LEAST TOXIC PEST CONTROL: HOW INFESTATIONS OF TERMITES, ANTS,
FLEAS, TICKS, AND BEETLES CAN BE CONTROLLED WITHOUT CAUSING
SHORT- OR LONG-TERM INDOOR AIR QUALITY CHANGES AND HEALTH RISKS
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION III, PHILADELPHIA, PENNSYLVANIA
NNEMS PROGRAM 1989, FRAN DOUGHERTY SUPERVISOR
LYNDA -M. MURRAY
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Disclaimer
This report was furnished to the U. S. Environmental Protection
Agency by the graduate student identified on the cover page, under
a National Network of Environmental Policy Studies fellowship.
The contents are essentially as received from the author. The
opinions, findings, and conclusions expressed are those of the author
and not necessarily those of the Environmental Protection Agency.
Mention, if any, of company, process, or product names is not to be
considered as an endorsement by the U. S. Environmental Protection
Agency.
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ABSTRACT
A number of least-toxic measures are discussed within the
framework of integrated pest management systems for termites, ants,
fleas, ticks, and beetles. It is presumed that adherence to such
programs minimizes changes in indoor air quality and also reduces
health risks by eliminating use of traditional, often hazardous
pesticides. Emphasis is placed on preventative measures such as
habitat modification and resource removal to eliminate conditions
that encourage the establishment of and foster the growth of pest
populations within the home. Control tactics are broadly
categorized as chemical, biological, and physical, and are detailed
in light of pertinent advances in research. Techniques relate
directly to the biology of the organisms and target periods of
vulnerabilty, symbiotic relationships between the pest and other
organisms, and basic physiological processes. Boron formulations,
insect growth regulators, and the use of extreme temperature seem
to have the most widespread applications, although "neem" products
may soon surpass even these advances.
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INTEGRATED PEST MANAGEMENT
Modern synthetic pesticides were first used during World
War II. Their effectiveness was great compared to that of
previous methods and their potential seemingly unlimited since
minimal hazard levels were perceived. Pest control operators
quickly came to depend on soil chemicals and "calendar" spraying,
often treating at the first sign of a pest with little or no
evaluation of the employed system. Exclusive reliance on chemical
controls has lead to a number of problems. One is the development
of resistance by the pest. First noted in cockroaches, flies, and
mosquitoes, resistance is now found in over four-hundred species
of pests. Indiscriminant use of certain chemicals has actually
selected for survivors in pest populations and has permitted
establishment of resistant progeny.
Another problem is resurgence. Non-selective pesticides can
remove the natural enemies of target pests and cause pest
populations to skyrocket. Similarly, elimination of the natural
enemies of potential pests can lead to secondary pest outbreaks.
Residues left by some pesticides also affect non-target organisms
and can build up in the food chain. Further, these residues can
be involved in synergistic phenomena in which the insecticide
combines with environmental factors that actually increase its
toxic effect.
Increased public concern over the use of insecticides and
the political organization of people affected by insecticides or
their residues pose a substantial hurdle for the continued use of
certain chemicals. Moreover, regulations regarding the
application of pesticides are becoming more stringent. Non-
renewable fossil-fuel, necessary for the manufacture and
application of synthetic pesticides, is in higher demand and the
cost of implementing traditional methods is rising as budgets for
control are declining. Fortunately, alternative measures in pest
control have been developed and there are a number of ways to
rationally and inexpensively combat pest problems. Given the
commercial availability of these newer techniques, traditionally-
used chemicals can be considered "last resorts"; to be employed
when alternative tactics fail and applied in a discrete way so as
to minimize exposure of non-target organisms.
Integrated 'pest management (IPM) is a decision-making
process in which one first determines if a pest suppression
treatment is necessary and, if so, answers questions regarding
when, where, and with what. It involves prediction of economic,
ecological and sociological consequences. In agricultural
settings, IPM programs have been developed for a variety of
crops. Pesticide use on these crops has dropped significantly,
while yield and quality have been retained, even improved. In
urban environments, IPM has been used to manage pests in parks,
gardens, and in many types of buildings. IPM concepts have also
been employed in forests when cyclic outbreaks of wood damaging
insects and diseases have occurred. While the term "IPM" has
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gained popularity, it has also been misused by institutions and
pest managers eager to jump on the bandwagon pulled by
enthusiastic consumers.
To clarify the meaning of the phrase, it is first necessary
to define the term "integrated". In part, the word implies the
fitting together of different treatment strategies into a total
management program. On this basis alone, many companies claim to
offer IPM programs. The definition is actually more complex,
since IPM programs are not mix-moshes of biological, chemical and
physical controls. Rather, the components are organized through
both monitoring and evaluation procedures, and careful decisions
are derived through consideration of economic, medical, and
aesthetic aspects of the treatment procedure. When IPM programs
are designed, interactions between key pests, their natural
enemies, potential pests, and other living and non-living factors
are also weighed.
In addition, IPM practitioners view pest management as a
single component within the context of ecosystem management. That
is, social, economic, political, and ecological factors all
influence pest management decisions. Aesthetic concerns of the
public are also considered, as well as government regulations
applicable to product marketing. IPM programs are consequently
transdisciplinary, relying on a variety of sources for input.
Contributions come from entomologists, plant pathologists, soil
scientists, architects, public health professionals,
sociologists, economists, etc. Essentially, information obtained
by IPM practitioners is woven into a coherent site-specific
strategy which aims at balancing the relationship between humans
and the species they regard as pests. It is the flexible nature
of IPM programs that make them so economically and aesthetically
sound. The use of natural pest controls such as disease agents,
predators, and parasitoids is maximized and artificial controls
are instituted only when pest populations threaten to exceed a
predetermined level of injury.
The objective of IPM programs is not to eradicate pests,
but to suppress their populations below a level which causes
unacceptable damage. It is generally desirable to permit a pest
to remain at low levels so as not to drive away its natural
enemies or to increase the risk of resistance development from
prolonged insecticide use. Pesticides never kill all their target
organisms; survivors go on to reproduce and pass along their
ability to detoxify the pesticides that are used against them.
Associated decreases in predator levels encourage the growth of
these surviving populations. By far the most energy- and cost-
effective pest management strategy involves consideration of the
human system within which pests find their resources. Through
appropriate building design and maintenance, and removal of food,
water, and harborage sites, the establishment of pest populations
can be significantly reduced.
There are six basic parts to an IPM program: (1) initial
information gathering to identify the pest and the problem, and
to delineate circumstances which may be contributing to the
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infestation; (2) monitoring at regular intervals to establish
fluctuations in the pest population or changes in the
environment; (3) establishing an injury level to predict if and
when the pest problem will escalate to the point of requiring
some sort of action; (4) record-keeping to note decisions made,
actions taken, and results; (5) selecting least-toxic treatments
which meet criteria regarding the least amount of hazard
presented to non-target organisms and the general environment,
and which are also economically-sound and likely to permanently
reduce the area's ability to support the pest; (6) evaluation of
the entire program to see how effective it is and if
modifications should be made.
The terms "monitoring" and "injury level" also need to be
defined. Monitoring implies regular inspections of areas in which
certain pests are likely to be found and most importantly
includes keeping records of the observations, paying attention
not only to the target organism but also to surrounding
influences such as human behavior and weather. Monitoring
programs should be tailored to the particular situation, and the
level of effort proportionate to potential damage, available
time, and the monitor's skill. For example, monitoring a
cockroach-infested kitchen may require only a bi-weekly
inspection of sticky traps acting as population gauges. In larger
systems such as forests and farms however, a more intensive
monitoring program may be required. In certain situations
potential pest and natural enemy populations are also monitored.
Key to the IPM concept is establishment of an "injury" or
"tolerance" level to indicate whether or not a problem is serious
enough to warrant treatment. The derived value takes into
consideration the amount of economic and aesthetic damage that
can be tolerated and is coordinated with a specific pest
population level. In agriculture, the degree of pest damage that
makes management worthwhile is relatively easy to determine.
Similar determinations are more difficult to make for building
infestations since opinions differ on tolerable levels of damage.
For example, people respond differently when asked how much
visibility of a pest or evidence of its activities is acceptable.
An initial injury level must therefore be set for the given pest
at the given site, but it should be noted that this level is
subject to change as the program continues. When an injury level
is suggested, it must be compared with field observations before
action is taken. Any pest management operation that does not
include periodic re-evaluation of injury level cannot rightfully
be called an IPM program since unnecessary activities can waste
resources and funds and can even exacerbate the existing
condition.
The purpose of this paper is to detail least-toxic methods
of prevention and control for termites, beetles, ants, fleas, and
ticks. Since the underlying framework is implementation of IPM
programs, each topic will be discussed with basic IPM questions
and approaches in mind. Due to the site-specific nature of IPM
programs, no exact prescription for control of these arthropods
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will be given. However, a-general outline of steps in a least-
toxic program is presented and a number of innovative techniques
are cited or alluded to. Much research has been done involving
the development of new insecticides, but because the focus has
often been on agriculture indoor adaptations can only be
suggested. I have therefore tried to concentrate on basic
techniques used against the most common house-invaders. There are
of course a number of pests that were not included in this
discussion and moreover, a number of control techniques not
mentioned or insufficiently described for the arthropods that are
discussed. Unfortunately, it is beyond the scope of this
preliminary review to focus on a broader range of approaches and
target pests. A good deal of material applicable to our
discussion awaits patent approval or scientific publication;
preempting such disclosures would be inappropriate.
-' r
•J
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BIBLIOGRAPHY
Olkowski, William, Helga Olkowski, and Sheila Daar. "What is
IPM?" Common Sense Pest Control Quarterly IV (3) (Summer
1988): 9-16.
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TERMITES
I. Identification of problem
A. Introduction
B. Termites in their natural environment
C. Termites as pests
II. Termite biology
A. Colony organization
B. Food sources and their need for symbiotic protozoa
C. Importance of soil and moisture
III. Termite detection
A. Introduction
B. Signs of termite presence
1. Gallery construction
2. Shelter tube formation
3 . Nesting habits
4. Presence of winged termites and shed wings
5. Other
IV. Monitoring
A. "Do-it-yourself"
B. Hire a professional
V. Termite prevention
A. Introduction
B. Basic preventative measures
1. Food removal
2. Reduction in available moisture
3. Removal of soil-wood interfaces
a) Basements and other areas
b) Crawl spaces
c) Slab-on-groud foundations
VI. Termite control
A. Introduction
B. Chemical methods of termite control
1. Introduction
2. Chemical control of subterranean termites: formation
of soil barrier
a) Barrier concept
b) Criteria a soil insecticide must meet
c) Screening
d) Activity
e) Repellency
f) Stomach poisons / protozoacides
g) Field testing
(1) "Ground board"
(2) "Concrete slab"
h) Chlorinated hydrocarbons
i) Other chemicals
j) Application methods
3. Chemical control of drywood termites
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a) Pretreatment of wood
b) Fumigation
c) "In-place" treatment
4. Wood extractives
a) Resistant woods and their resistant properties
b) Isolation of resistant species
c) Repellent and distasteful woods; wood
extractives as protozoacides
d) Extraction of resistance components
e) Uses for antitermitic compounds derived from wood
5. The bait block method and the use of insect growth
regulators
a) Bait block method as a viable alternative
b) Goal; advantages; baits; toxicants
c) Mechanism
d) Testing
e) Juvenile hormones
f) Juvenile hormone analogs and their effects
g) Examples of juvenile hormone analogs and their
consequences
6. Antibiotics used to eliminate symbiotic protozoa
7. Liquid nitrogen as a control for drywood termites
C. Biological control of -termites
1. Termites and fungi
2. Termite predators
3. Termite parasites
a) Nematodes vs termites
b) Controversy
4. Termite pathogens
D. Physical methods of termite control
1. Uses of extreme heat
2. Sand barriers for the control of subterranean
termites
3. Digging up subterranean termites
4. Termite control by electromagnetic devices
5. Electrogun™
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TERMITES
I. Identification of problem
A. Introduction
The order Isoptera contains many economically important
insects. There are six families which exist worldwide:
Kalotermitidae (drywood termites), Termopsidae (dampwood
termites), Rhinotermitidae (subterranean termites), Termitidae
(mound-building termites), Mastotermitidae, and Hodotermitidae
(harvester termites). The three families found in the United
States are Kalotermitidae, Termopsidae, and Rhinotermitidae. The
latter of these will be emphasized in our discussion.
B. Termites in their natural environment
In their natural habitat, termites are highly beneficial
insects. They work along with decay fungi to break down dead or
dying plant material, returning chemical elements in the wood to
the soil. Their role in the nutrient cycle is therefore
important, and attempts to control them need only be made when
human possessions are attacked or threatened.
C. Termites as pests
Termites have become "pests" for a few reasons. In clearing
forested areas for construction we remove cellulose, termites'
natural food source. Wooden structures which replace lost plant
material are then exploited as an alternative resource. The
estimated value of wood-containing, single-family units in the
United States was about 2.5 trillion dollars in 1980. This
amount, plus the unknown value of multifamily units, government-
owned buildings, and other wooden products, represents a
significant portion of the United States's net worth and should
signal prompt pursuit of wood preservation techniques.
Unfortunately, available, effective, and often inexpensive
preventative treatments are neither widely nor consistently
employed. Poorly designed slab-on-ground construction, increased
use of concrete and masonry adjacent to foundation walls, and
other home and yard alterations are often associated with lack of
preventative measures, impairment of prior chemical treatment
and exposure of vulnerable surfaces. Factors such as these
inflate the cost of control and unnecessarily deplete our
valuable wood resources.
Of the 2,200 species of termites known worldwide, sixty-
nine infest buildings. About fifteen species found in the United
States damage human dwellings, community buildings, and various
wood products. Subterranean termites are considered the most
destructive and economically important family. They occur
throughout the United States, except in Alaska, and are most
numerous and destructive in warmer regions. The predominant
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subterranean termites are Coptotermes formosanus Shiraki. and
species of the genera Reticulitermes and Heterotermes. Costs for
damage and control of termites may exceed an estimated 750
million dollars annually, with subterranean termites accounting
for about 95 percent of the total loss. Much of this percentage
can be attributed to species of Reticulitermes which are
widespread on the mainland. Heterotermes aureus (Snyder) is a
major pest in the desert Southwest, and Coptotermes formosanus
Shiraki attacks buildings in Hawaii (although it also damages
structures in southern states).
The southeastern part of the United States is considered to
be a "high hazard" area, with an untreated building having an 80-
100 percent chance of being attacked by subterranean termites
during its lifetime. The northern third of the United States is a
"low hazard" area with structures running a 0-50 percent chance
of attack. Other zones of the country are "moderate hazard"
areas, with buildings having a 50-80 percent chance of
infestation. These differences allude to the importance of
understanding termite biology in order to predict activity
patterns and select appropriate control measures.
The most destructive drywood termites occur in the southern
and southeastern coastal states, and in Arizona, California, and
Hawaii. They include Cryptotermes brevis Walker, Neotermes
castaneus (Burmeister), and species of Incisitermes. The dampwood
termites Zootermopsis angusticollis (Hagen) and Z. nevadensis
(Hagen) damage wood in Oregon, Washington, and California.
Paraneotermes simplicicornis (Banks) attacks buildings, shrubs,
and trees.
II. Termite biology
A. Colony organization
All termites live in highly organized social communities.
Individuals begin as transparent eggs and go through a larval
stage before maturing into workers, soldiers, reproductives
(future kings or queens), or secondary reproductives. Adults of
these castes each have different physical features and behavioral
roles
Workers are sterile, wingless, soft-bodied, and light in
color. Their duties may include the following: caring for eggs
and young, feeding and cleaning other colony members, foraging
for food, and constructing and maintaining shelter tubes.
Although workers are not found in drywood termite species, they
generally represent the most numerous caste and are often the
colony members seen in an infested sample. Because workers are
the damaging wood-eaters, they represent strategic targets when
defining control programs. Sometimes, workers become secondary
reproductives which supplement the number of eggs laid by the
queen. Soldiers have enlarged brownish heads and long mandibles
(mouthparts). Their job is to defend the colony against
predators, particularly ants.
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Sexual adults (reproductives) are black or yellow-brown in
color with two pairs of equally long wings. In contrast to winged
termites, winged ants have wings of unequal length, bent not
straight antennae, and hard bodies with thin waists and pointed
abdomens. Only a few termite workers develop into sexual adults,
and not many of these reproductives survive their short dispersal
flight from the mother colony. Most are eaten by predators (other
insects and birds) or suffer desiccation. Surviving males (kings)
and females (queens) shed their wings and establish pairs, then
excavate a cell in or near wood in the ground and mate. Most
species in the United States lay less than one hundred eggs in
the first year, but this number normally increases with the age
of the colony. A five-to-six-year-old colony may have several
thousand members, and produce winged reproductives yearly.
B. Food sources and the need for symbiotic protozoa
The principal food of termites is cellulose, a constituent
of wood and other plant tissues. Qualifying foodstuffs include
not only wooden building components but also utility poles, paper
products, and fabrics derived from cottons and other plants. When
searching for food, termites may also damage non-cellulose
materials such as plastic. Foraging tunnels made in wood are
called galleries. A preference for soft spring wood over harder
summer wood often leaves the food source layer-like and hollow-
sounding.
Subterranean termites and drywood termites both maintain
symbiotic associations with gut protozoa. These protozoa,
essential for digestion, are responsible for the initial
enzymatic breakdown of cellulose in ingested material. Drywood
termites excrete undigested lignin in the form of hard pellets
which are stored in their galleries. (Lignin is the stiffening
substance found in the secondary walls of plant cells.)
Periodically, these six-sided pellets are pushed out through
small "kick holes" made in the wood. In contrast, subterranean
termites plaster their excretions on gallery walls. They also use
their excrement to form delicate honey-comb structures within
galleries, and to cement soil particles together when creating
protective shelter tubes.
C. Importance of soil and moisture
Aside from cellulose, the presence of soil and moisture
are, to varying degrees for each family, key elements in termite
survival. Soil serves three main functions: it provides a source
of moisture to prevent soft-bodied termites from drying out, it
serves in protection against predators, and it is employed as a
building material for construction of above-ground shelter tubes.
Since some termites carry soil with them, termite presence can be
accompanied by that of wood fungi and consequently, wood decay.
Drywood termites are least dependent on the soil and are able
to build above-ground nests in sound dry wood. Dampwood termites
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however must nest in moist decaying wood, even though they can
extend tunnels into drier parts of the wood. Subterranean
termites require the greatest amount of moisture. They live in
the soil and tunnel through it to reach wood located above
ground. Sometimes this foraging behavior necessitates
construction of protective shelter tubes. These passages reach
from the soil to above-ground food source and reduce the risk of
desiccation and attack by predators.
III. Termite detection
A. Introduction
Discovering damage to wood and wood products, and
identifying the causative agent can be accomplished by the lay
person. Findings can be confirmed by a professional from a local
Cooperative Extension Service, college entomology department,
natural history museum, or pest control company. When inspections
are done by the homeowner, the first place to look for damaged
wood members is where water collects. To distinguish termites
damage from other types of wood damage the following should be
kept in mind. Fungi are generally associated with wood that is
discolored, shrunken, and weakened. Insects are associated with
wood that has holes, tunnels, galleries, or chambers on or
beneath the wood surface. Holes less than a half-inch in diameter
signal the presence of wood-boring beetles; holes greater than a
half-inch in diameter are indicative of carpenter bees. The
presence of galleries or chambers that are easily penetrated with
a screwdriver signify termites. The basic signs of subterranean
termite presence are outlined below; most have already been
mentioned.
B. Signs of termite presence
1. Gallery construction
There are various signs of subterranean termite activity.
One is the presence of feeding tunnels or galleries within
infested wood. Subterranean termite galleries run along the
wood's grain and are marked with grayish specks of excrement and
soil. These termites do not reduce wood to a powdery mass or push
wood particles to the outside as other wood-boring insects do.
Drywood termites cut clean galleries against the wood's grain.
Fecal pellets, pushed outside, often collect in nearby piles.
Because drywood termites usually damage wood less quickly than
subterranean termites do, the structural weakening they cause is
most likely to be seen in older buildings.
2. Shelter tube formation
Earthen shelter tubes, often seen extending over the
surface of foundation walls, are another sign of an active
subterranean termite colony, especially if they are quickly
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rebuilt when tampered with. Shelter tubes are characteristic of
subterranean termites exclusively.
3. Nesting habits
Most subterranean termites found in the United States do
not construct clearly defined nests. However, the Formosan
termite (Coptotermes formosanus Shiraki) builds what is called a
"carton nest". It is made of chewed wood, saliva, and feces, and
serves to retain moisture as well as provide protection from
predators. Carton nests permit above-ground colony establishment
and become dry and hard when not occupied. Formosan termites are
notably more aggressive tunnelers and consumers than species of
Reticulitermes.
4. Presence of winged termites or shed wings
The presence of winged termites (reproductives) or shed
wings, often near windows or lit areas, also indicate termite
presence. Such evidence suggests that winged termites have either
emerged within the building and have been unable to escape, or
that they have been drawn to the lights of the house from
outside.
5. Other
Aside from these rather obvious signs of subterranean
termite activity, one can predict where an infestation is likely
to be found if one reflects on basic termite biology. Since
termites seek out cellulose products, soil, and moisture, they
should be found in areas supporting such resources, for example,
beneath buildings and decks, and around leaky pipes and wet wood.
IV. Monitoring
A. "Do-it-yourself"
It is .believed by some researchers that annual monitoring
is a very effective way to see and treat termite problems, and
that it can essentially negate broad scale use of toxic
pesticides. Monitoring entails careful inspection of the
residence for conditions conducive to establishment of termite
colonies. Inspections can be done by the owner, a professional,
or both. Homeowners, when working alone, should first walk around
the house and record its dimensions on grid paper. This sheet can
be duplicated for note-taking during subsequent monitoring.
Attention should be paid to conditions that attract termites such
as chronically damp wood or soil (for subterranean termites), or
dry caked areas of wood (for drywood termites); the signs listed
above can serve as indicators of termite activity.
When monitoring, it is advisable to wear coveralls, a
helmet, and gloves since many of the areas that should be checked
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are cramped and hard to reach. A flashlight, a screwdriver for
probing, and a hammer for sounding are all helpful tools. A
moisture meter with a range of 15-24 percent, a pencil, a
clipboard, grid paper, and a measuring tape are also useful. A
ladder may be required to reach roof and attic areas. Inserting a
hacksaw under the sills or headers of earth-filled porches near
crawl spaces can be used to detect deterioration (the blade
should not go beyond the sill or header). Caulk can be brought
along for quick seals.
These exterior sources of trouble should be carefully
inspected: foundations, brick or stucco veneers, foundation air
vents, plumbing areas, planters and trellises, and window and
door casings. Indoors, inspection should center on areas that are
stained or have mold growth, on sagging or buckling floors, and
on attached rooms and garages. Simply put, any area prone to
moisture retention, separation, or decay is a potential termite
entry point.
B. Hire a professional
If a professional is chosen for the monitoring, the company
should offer annual termite monitoring services for a fee
separate from that of treatments. It is important to remember
that most termite infestations are slow to cause damage and that
a pest control company should not pressure a client into
contracting for treatments. Paying a separate fee for monitoring
may help ensure that the consultant offers an unbiased opinion of
the situation. Clients can request to see samples of insects and
decayed wood found during monitoring.
One advantage to having a professional do the monitoring is
the use of dogs by pest control companies. These dogs (usually
beagles) are specially trained to smell and hear wood-damaging
insects. They are able to search where humans cannot gain access
and can detect infestations missed by pest control operators. The
dogs are insured for errors and results obtained with their help
are admissable in court should any lawsuits arise. Although this
type of inspection is somewhat more expensive than the regular
kind, the cost is justified by increased efficiency.
Unfortunately, this service is not widely available and it
appears that consumers will have to encourage pest control
companies to offer it.
When inspection results are in, homeowners can decided
whether or not treatment is necessary. If it is, then the most
effective but least-toxic procedure can be delineated. If a pest
control operator is hired to do the work, he should be familiar
with alternative treatments and be willing to implement them
reliably and in close consultation with the client. When a least-
toxic program is pursued, an educated consumer is key to
obtaining satisfactory results.
V- Termite prevention
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A. Introduction
Probably the most effective and least costly time to
protect against subterranean termite damage is during the
planning and construction of a building. Three main types of
prevention may be considered: removal of wood debris and other
food sources, reduction in available moisture, and elimination of
soil-wood interfaces. Other, more direct methods of prevention
will be considered later in our discussion.
B. Basic preventative measures
1. Food removal
Before construction begins, all roots, stumps, and wood and
paper debris should be removed from the building site. Wooden
spreader sticks and grade sticks should be removed before the
concrete hardens. Form boards and scrap lumber need to be
discarded before filling and back filling are done around
completed foundations. Elimination of such items denies termites
food sources and accessways to building members during and after
construction.
2. Reduction in available moisture
Moisture sources used by termites include the water
contained in unseasoned wood, rain and ground water,
condensation, and water from plumbing leaks. Termites feed mostly
on wood wetted by rain seepage, soil, or leaky pipes. Buildings
should therefore be designed and constructed so as to permit
rapid drainage of water, particularly from foundations and roofs.
On roofs for example, heat from the attic can melt snow
lying above. The water then runs down the roof and freezes on the
overhang which is cooler. Additional water collects behind this
"ice dam" and soaks under the shingles, often resulting in
damaged ceilings or walls. Such consequences can be prevented by
increasing attic insulation and by inserting flashing to protect
the area under the shingles.
Shingles often present another problem. In the past, they
were placed without paper on narrow wooden strips which permitted
both inward and outward drying after rains. Today, since shingles
are usually laid directly on solid plywood, drying is restricted.
Adding to potential water collection is the tendency for modern
roofs to be of low pitch. This further slows drying and allows
soggy organic matter to accumulate. Given these trends, treating
shingles with a wood preservative appears to be the best
preventative measure.
The outside finished grade at a building site should be
equal to or below the level of soil beneath the structure. This
stops water from becoming trapped under the structure and also
exposes the foundation wall which facilitates inspection for
termite activity. Gutters and downspouts attached to eaves also
help move water away from a building. In certain instances, it
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may be necessary to install drainage tile around a building's
foundation.
Ventilation openings, found in foundation walls beneath
buildings with crawl spaces, need to be sufficiently large and
properly distributed so as to prevent formation of dead air
pockets. These pockets give rise to humid conditions favorable to
termite infestations. Cross ventilation is best achieved when
openings are within ten feet of the building's corners. Care must
be taken so as not to obstruct ventilation openings with
shrubbery and thereby prevent inspection.
3. Removal of soil-wood interfaces
a) Basements and other areas
Certain preventative measures should be taken to decrease
the availability of soil-wood connections. The formation of
physical barriers (e.g. increased distance between soil and
desirable building parts) serves this purpose. Such barriers
force subterranean termites to build shelter tubes which convey
their presence. For example, siding should not extend more than
two inches below the top of foundation walls, piers, or concrete
caps, and should be six inches above the outside grade. An
eighteen inch minimum clearance between the ground and the bottom
of the floor joists should be allowed, and clearances for beams
and girders should be twelve inches.
Porch supports should be separated by two inches from the
building to prevent hidden entry, and wooden steps should rest on
a concrete base six inches above the ground. Door frames and
jambs should not extend through concrete floors, and window wells
near the outside grade should be at least six inches below the
nearest piece of wood. Wooden partitions, posts, and stair
carriages in basements need to be installed after the concrete is
poured and should not extend through the concrete. Wood used in
basements should be pressure treated with a wood preservative.
Metal termite shields have been used as replacements for
concrete caps usually placed atop masonry foundations. If
correctly designed, installed, and maintained, a shield will
force termites to create revealing tunnels around and over their
bent-down edges. However, since these shields are often
improperly used, they are not presently recommended for detection
and prevention of termites.
b) Crawl spaces
In crawl spaces, all plumbing and electrical conduits must
be kept off the ground, suspended from girders or floor joists
but not supported by wood blocks (an easy area for termites to
tube over). Generally, it has been advised to chemically treat
the soil around basements and crawl spaces, and to fill gaps in
foundation walls or concrete slabs if pipes penetrate these
areas. Spaces under concrete porches, entrance platforms, and
other raised units should not be filled with soil. Rather, they
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should be left open, with access doors for inspection. If soil
filling is necessary, it is sometimes advised to chemically treat
the soil and keep it six inches from nearby wood sources. The
most termite resistant type of foundation in buildings with crawl
spaces is of poured concrete with reinforced piers to prevent
large shrinkage or settlement cracks (a .03 inch space is enough
for termite entry). The least resistant type of crawl space
construction employs only pressure-treated piers.
c) Slab-on-ground foundations
Certain homes, with neither basements nor crawl spaces,
have concrete slab-on-ground foundations. This type of
construction is very prone to termite attack. Termites can reach
the building by going over the edge of the slab, or by going
through expansion joints, openings around plumbing, or cracks in
the concrete. Infestations occurring under these circumstances
are difficult to control and chemical treatment of the soil,
before the concrete is poured, has been recommended to prevent
attack. The best type of slab-on-ground construction is use of a
"monolithic slab". In this case, the floor and footing are poured
in one continuous operation, eliminating vulnerable joint areas.
The next-best type of slab-on-ground construction involves
a "suspended slab". This slab extends across the top of the
foundation and is constructed independently of it. It prevents
hidden entry as long as the lower part of the slab is open to
view. The least resistant type of slab-on-ground construction is
the "floating slab" in which the slab rests on the foundation's
ledge or is independent of it. In either case there is direct
connection between the soil, expansion joints, and the foundation
walls.
Other preventative measures include: inspection of all new
wooden articles (e.g. furniture, picture frames, and crates) to
avoid introduction of an infestation; caulking outside cracks and
joints, and painting or varnishing all wooden surfaces;
inspecting under siding, and between and under wood and
fiberglass shingles; and timing building construction so that it
does not coordinate with the swarming of termites.
VI. Termite control
A. Introduction
Control of each group of termites is facilitated by an
understanding of the given family's physiology, behavior, and
basic reguirements. For example, the control of drywood and
subterranean termites should be approached differently if one
considers the amount of moisture each needs. Drywood termites
require only the amount of moisture absorbed by air-dried wood
whereas subterranean termites reguire more than that amount.
Treatments for drywood and subterranean termites could therefore
focus on, respectively, wood pretreatment and chemical barriers
in the soil. Generally, termite control indoors involves
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eliminating conditions that favor the formation of termite
colonies in the soil and that permit passage to wood within a
building. Indoor control relies on inspection, sanitation, and
chemical control. To simplify discussion of the available methods
of termite control, I have broadly classified treatments as
"chemical", "biological", and "physical". (This scheme is
followed throughout subsequent sections.)
B. Chemical methods of termite control
1. Introduction
Traditionally, termite control operations have stressed
the application of insecticides. These substances (e.g. the
fumigant methyl bromide and the liquid chlordane) are among the
most toxic approaches available. Increased concern regarding
associated health and environmental hazards, highly-publicized
accidents by poorly-trained pest control operators, new
government restrictions, and the increased availability of
alternative control techniques have set the stage for re-thinking
traditional methods and developing newer, less toxic approaches.
However, situations remain in which the use of insecticides to
control termites is still warranted. In such cases, there are two
ways to lessen potential health hazards. One is to restrict
application of a traditional insecticide, the other is to select
a non-traditional insecticide.
2. Chemical control of subterranean termites:
formation of a soil barrier
a) Barrier concept
Subterranean termites are best controlled by the
preventative measures outlined in the previous section. However,
complete control by these methods is difficult and sometimes
expensive. It is commonly believed that the most effective and
least costly program combines good construction practices with
creation of a chemical barrier between the soil in which the
subterranean termites live and the desirable cellulose sources
above. Termites living in the soil under and around a building
meet with the barrier when they are foraging. While some soil
chemicals kill termites, most serve as repellents that force the
insects to travel in a different direction.
b) Criteria a soil insecticide must meet
Before a chemical is selected for screening as a soil
insecticide, it must exhibit relatively low mammalian toxicity.
That is, greater than 500 mg/kg oral LD50, greater than 2000
mg/kg dermal LD50, and greater than 2 mg/1 inhalation LD50. The
chemical must also have low water solubility (less than 50 ppm),
and exhibit stability on the soil. Other considerations include
the chemical's effect on non-target soil insects and its
marketing potential.
n
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c) Screening
Screening potential soil insecticides in the laboratory
serves two purposes. First, it saves time and money which would
otherwise be spent on extensive field testing of ineffective or
short-lived chemicals. Second, screening isolates chemicals which
are persistent, that is, are toxic or repellent to termites for a
long period of time. Apparently persistent chemicals are further
tested in laboratory and field studies. The chemicals are
screened against R. virginicus (Banks) and C. formosanus Shiraki.
d) Activity
The activity of selected chemicals is determined by
restricting worker termites to a thin layer of treated soil in a
Petri dish. Changes in behavior and physiology are noted over an
eight hour period. If the specimens become moribund or die when
exposed to a wide range of concentrations (0-1,000 ppm wt/wt),
the chemical is selected for follow-up tests. Treated soil is
stored and bioassayed at six month intervals to verify
persistence of termicidal activity. If effectiveness is
maintained while on the soil, the chemical is tested in the
field.
e) Repellency
Chemicals which are repellent but not toxic to subterranean
termites are also studied. In tests concerning these chemicals,
termites are allowed to "choose" between treated and untreated
soil. If a statistically significant number of termites remain on
the untreated soil, the chemical is considered to be repellent.
If it is repellent over a wide range of concentrations, the
treated soil is stored and bioassayed at six month intervals.
Ideally, a chemical should be both repellent, and toxic on
contact (even brief contact with some chemicals can result in
delayed mortality).
f) Stomach poisons / protozoacides
Chemicals which are neither toxic nor repellent in eight
hour bioassays on soil are retested using powdered cellulose to
see if the chemical can act as a stomach poison. For two weeks
termites are exposed to dyed and treated cellulose. Their
physical condition and the guantity of dye in their gut is
monitored daily. After this time, hindgut protozoa are counted.
If there is a significant drop in protozoan number, the chemical
is subseguently evaluated as a protozoacide in "choice" and "no-
choice" tests. If termites feed on the treated cellulose and if
the chemical is slow-acting, it is considered for the "bait
block" method of control (to be discussed later, in connection
with insect growth regulators).
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g) Field testing
Field evaluation is the final and most time consuming phase
of testing prior to registration of the chemical with the United
States Environmental Protection Agency. A minimum of five years
efficacy data from four nationwide locations is required. These
evaluations are performed by the United States Department of
Agriculture Forest Service at sites throughout the mainland, and
on Sand Island of the Midway Atoll and in Panama. These sites
were chosen to represent semiarid, temperate, subtropical, and
tropical climates.
(1) "Ground board"
Two field tests are used to assess a termiticide's
effectiveness: the "ground board" and the "concrete slab". In the
ground board method a seventeen square inch area of soil is
cleared and then soaked with a known concentration and volume of
a chemical solution. A sapwood pine board is centered atop the
treated area and weighed down. Termites must penetrate the
insecticidal barrier to reach the desired wood. If termites fail
to attack the board, the barrier is considered effective.
(2) "Concrete slab" '
The concrete slab method simulates conditions associated
with slab-on-ground types of construction. The soil is treated as
in the ground-board tests, then covered with a polyethylene vapor
barrier. A plastic pipe four inches in diameter, placed in the
center of the soil, serves as an inspection port. The vapor
barrier around the pipe is covered with a one inch layer of
concrete. This test was developed in response to the introduction
of organophosphate and carbamate insecticides which are subject
to degradation by sunlight and leaching in exposed conditions,
but are effective under and around buildings. With both these
methods, treatments are replicated a number of times and the
boards are examined annually. Once a treatment board is attacked,
it is discounted and no longer examined.
h) Chlorinated hydrocarbons
Subterranean termites have been successfully controlled for
more than thirty years by chlorinated hydrocarbons. Chlordane,
heptachlor, and a chlordane-heptachlor mixture were frequently
used termiticide formulations. In tests conducted by the Forestry
Sciences Laboratory in Gulfport, Mississippi, the following
chlorinated hydrocarbons were found 100 percent effective for the
stated duration: 1.0 percent chlordane, thirty years; 0.5 percent
heptachlor, twenty-six years; and 0.5 percent aldrin and
dieldrin, twenty-nine years.
While these chemicals are very effective, they are also
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capable of accumulating in the food chain, and their persistence
makes them potential soil contaminants in residential areas which
have been converted for other (recreational) purposes. Further,
their use has created the illusion that regular monitoring and
habitat modification are unnecessary. It has been shown that
termites can reappear even in treated areas (the recurrence rate
is however lower than that associated with buildings which have
neither been treated nor monitored).
If expectations concerning these chemicals could be
lowered, say to an 80-100 percent level of effectiveness for a
seven to ten year period, then chlordane for example could be
considered effective at concentrations as low as 0.125 percent in
the United States (provided the proper volume of treating
solution is applied). Risks may also be minimized by confining
the application of these chemicals to areas removed from the
resident, such as under concrete slabs or beneath soil barriers
which would prevent vapors from entering the home through heat
ducts or other openings.
i) Other chemicals
Other termiticides, currently used and registered with the
EPA, include: chlorpyrifos, cypermethrin, fenvalerate,
isofenphos, and permethrin. All can be bought from certified
pesticide applicators and used with their supervision.
Chlorpyrifos can be purchased and used by homeowners only in some
states. These chemical solutions are least expensive and easiest
to prepare when purchased as liquid concentrates formulated
according to the percent of toxicant contained. Each concentrate
contains an emulsifier to make it mixable with water, and each
must be diluted before use. Recommended final dilution
concentrations are as follows: 1.0 percent chlorpyrifos, 0.25 -
0.5 percent cypermethrin, 0.5 - 1.0 percent fenvalerate, 0.75
percent isofenphos, and 0.5 -1.0 percent permethrin. It may be
viewed as a small concession that one commonly used chlorpyrifos
formulation DursbanR, an organophosphate, has a shorter life-span
(eleven to fourteen years) than the chlorinated hydrocarbons.
But, its LD50 value of 135 mg/kg falls between that of chlordane
(LD50 = 250 mg/kg) and aldrin (LD50 = 38 mg/kg) . Note that the
lower the LD50 value, the greater the material's toxicity.
j) Application methods
Chemicals may be applied with a power sprayer or tank-type
garden sprayer using low pressure to prevent misting. The type of
soil involved and the amount of moisture it contains both affect
the rate of solution acceptance. Excessively wet soil leads to
runoff and prevents proper penetration of the chemical; frozen or
dry soil causes puddling and prevents even distribution of the
chemical. Damp soil offers the greatest acceptance. It is
important to note that treated soil must be protected from
mechanical disturbance since even slight losses in barrier
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continuity increase the risk of termite entry. For example,
treatment of fill under slabs is less than two inches deep, with
most of the chemical concentrated in the top three-fourths of an
inch. It is easy to see how intolerable even slight disturbances
in such areas are. Final treatment on the outside of foundation
walls should be done after all grading and disruption are over.
Treated soil can also be washed away by rain, so it may be
necessary to cover areas if concrete is not poured soon after
soil treatment. Most soil insecticides stay put once they are dry
and are most often insoluble in water, so leaching is usually not
a concern. But, water supplies can be contaminated if the
insecticide is applied to soil containing layers of gravel or to
soil which tends to crack in droughts.
If a chemical barrier is not established prior to pouring
the concrete in a slab-on-ground foundation, and if an
infestation is later discovered, a chemical barrier can still be
created. A series of half-inch holes drilled vertically into the
slab about eighteen inches apart are each injected with the
chosen chemical in such a way that overlap provides adequate
coverage of the soil. Holes may also be drilled horizontally
through the exterior foundation to the soil just beneath the slab
and the chemical injected through these ports.
3. Chemical control of drywood termites
a) Pretreatment of wood
There are three commonly accepted methods of drywood
termite control: pretreatment of wood, fumigation, and "in-place"
treatment. Pretreatment of wood entails treating lumber with a
preservative, either by a pressure or non-pressure process,
before the wood is used. Some common preservatives are creosote
and creosote solution, oil-borne preservatives
(pentachlorophenol), and water-borne preservatives (inorganic and
metallic salts). The pressure process provides long-term
protection against drywood termites as well as subterranean
termites and wood decay fungi. The degree of protection gained by
the use of chemically treated woods depends on the kind of
preservative used, the degree of penetration, and retention of
the chemical in the wood. Preservatives must be applied at
standard retention rates and satisfactory penetration attained.
Maximum protection is achieved through pressure impregnation
using an approved chemical.
Pretreated wood can be considered part of a "least-toxic"
program because it can be used in a limited area during
construction and as a replacement for damaged or hard-to-monitor
wood in susceptible areas. Of the materials used to pretreat
wood, those containing copper are the least toxic. Since
pentachlorophenol, arsenicals, and creosote products pose health
hazards are on the EPA's restricted materials list, and will
eventually be unavailable without a permit, new preservatives
will be sought.
Marketed preservatives of relatively low toxicity have the
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following as active ingredients: copper naphthenate, copper-8-
quinolinolate, zinc napthenate, polyphase (3-iodo-2-propynl-butyl
carbamate), TBTO (bis-tributyl-tin-oxide), and TBTO / polyphase.
For soaking the wood, follow the label instructions. (Soaking is
preferred over brushing since it increases absorption of the
preservative.) When treating the wood yourself, it is advisable
to wear a respirator with an activated charcoal filter, and to
use washable or disposable gloves. To further decrease the amount
of preservative you apply, the chemical can be used just on the
most vulnerable part of the lumber which is the end, taking care
that the treatment is done after the item is trimmed. A mask
should be worn when sawing treated wood to prevent inhalation of
the sawdust.
Compared to the above preservatives, a recipe given by the
USDA Forest Service is even less toxic, but still provides a high
level of protection for treated woods. The active ingredient is
copper-8 quinolinolate, the only wood preservative approved by
the Food and Drug Administration for use on tables with which
food or humans make contact. The active ingredient is combined
with the Forest Product Laboratory's water-repellent formula in
these proportions: 12 ounces of boiled linseed oil, 1 ounce of
melted paraffin wax, 105 ounces of solvent (paint thinner), and
9.5 ounces copper-8 (10 percent concentrate) to 0.75 percent
copper-8.
b) Fumigation
Although fumigation can kill all termites existing in a
structure, it is an expensive procedure and reguires that the
area be evacuated for a day or two until the poisonous vapors
dissipate. The infested building is draped with an airtight
covering of nylon or polyvinyl chloride and the fumigant is
introduced in several areas under the cover. Sulfuryl chloride
(VikaneR) , at 1 pound per 1000 cubic feet of space and at a
temperature of seventy degrees Fahrenheit or above, can be used
if the building is kept covered for twenty-four hours. Methyl
bromide is effective at 2-3 pounds per 1000 cubic feet. Aside
from fumigation being expensive and inconvenient, the chemicals
are highly toxic and do not provide permanent protection. Once
the fumigant has dispersed reinfestations can occur, although
fumigation should not be needed for another six to eight years.
Some pest control operators use vaults to fumigate small infested
articles.
c) "In-place" treatment
"In-place" or spot treatments refer to application of
insecticides only to areas where termites have been detected or
where monitoring is difficult. This technique stands in sharp
contrast to traditional recommendations of applying long-lasting
insecticides to every potential infestation site. Least-toxic
spot treatments are considered most effective when combined with
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habitat modification, biological controls, and/or physical
controls.
Localized infestations can be controlled by the "drill and
treat" method, a process which involves drilling small holes into
infested wood and injecting toxic chemicals. Chemicals which are
commonly used include Perma-Dust PTR 240, PTR 270 Dursban", PTR
250 Baygon", and PTR 2230 Tri-Die. But, since this method
protects only select areas and because thorough application can
be difficult, termites are not always eliminated. Heavy-bodied
oil emulsions containing pentachlorophenol and heptachlor have
also been used to treat wood surfaces.
A less toxic alternative to these spot treatments is
offered by the use of desiccating dusts. These dusts can be
applied during construction to prevent infestations or after
fumigation to prevent reinfestations. A desiccating dust can be
abrasive or sorptive in nature. That is, it can either abrade or
absorb the waxy layer on an insect's outer coat, causing
dehydration and eventually death. Diatomaceous earth, a powder
made from naturally-occurring deposits of fossilized diatoms,
functions both to abrade and to absorb. It is found as an inert
in a number of products and works against many pests. It is safe
enough to be added to grain in storage to eliminate pests, and
can be used as an additive in animal foods for control of
intestinal parasitic worms in cows, horses, and dogs. (The form
of diatomaceous earth discussed here is not the glassified sort
used for swimming pool filters.)
Silica dust is sorptive in nature. It comes in two forms,
amorphous precipitated silica (not to be confused with the
crystalline form that causes silicosis in industry workers) and
silica aerogel. Both prevent drywood termite attack. Silica gels
are highly effective due to their large specific surface areas,
adequate pore diameter, and low sorptivity for water, Dri-die 67R
has been used for over twenty years and has a low mammalian
toxicity (LD50 > 3,160 mg/kg). Laboratory feeding tests report no
toxic effects in test animals and no pathology observed in
laboratory rats feed up to 25,000 ppm for twenty-eight days.
DrioneR appears to be even safer with an LD50 value of over 8,000
mg/kg. DrioneR contains 40 percent amorphous silica aerogel, 1
percent pyrethrins (a plant derivative added for quick kill or
knock-down), and 49 percent petroleum distillate (carrier). It
also contains the synergist piperonyl butoxide which allows the
product to supply 60 percent more ammonium fluosilicate than Dri-
die1'. Ammonium fluorosilicate enhances the product's
effectiveness by conferring a positive electrostatic charge to
the silica gel particles which enables them to adhere better to
the target insect. The charge dissipates after a few months and
effectiveness of the dust is reduced to that of an unfluorinated
silica gel. Because fluorine is an environmental contaminant,
there is controversy over use of the synergist.
Silica gels are useful in confined areas such as attics for
drywood termites, in sewers and wall voids for cockroaches, and
in the house and yard for young fleas. Generally, silica aerogel
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is used in attics at the rate of 1 pound per 1,000 square feet to
prevent winged drywood termites that enter via crawl spaces from
boring into the wood. While actively crawling about, the termites
pick up the dust and die in as little as two hours. It has been
noted that even small amounts of silica aerogel dusted onto wood
blocks will prevent feeding by exposed termites and consequently
limit their survival to about two weeks. (Termites in non-treated
controls were meanwhile feeding vigorously.) Silica aerogels are
inorganic and not subject to decomposition, and they offer
protection for the life of the treated building. However, they
are toxic to fish and should not be allowed to contaminate
natural bodies of water or home aquaria. When using these and
other, even non-toxic dusts, it is advisable to protect yourself
with goggles and a dust mask. Signs posted in the treated area
are helpful to future residents and inspectors.
4. Wood extractives
a) Resistant woods and their resistant properties
Work done at the Southern Forest Experiment Station in
Gulfport, Mississippi has involved the use of wood extractives as
termiticides. It is known that certain woods are more resistant
to termite attack than others and that resistant species include
bald cypress, eastern red cedar, chestnut, Arizona cypress, black
locust, redwood, osage orange, black walnut, and Pacific yew.
Resistant properties result from chemical constituents of the
wood which are distasteful, repellent, or toxic to termites.
b) Isolation of resistant species
A study conducted by Carter and Dell (1981), aimed at
isolating species of resistant American wood, determined the
survival and feeding responses of R. flavipes (Kollar) on
selected species of hardwoods. Heartwood blocks were cut from
forty North American hardwood species which represented twenty
families. Blocks from each board were tested using workers taken
from three out of nine available colonies (this minimized the
effects of biological variation of the termites on the test
results). After eight weeks of exposure to the blocks, surviving
termites were counted. The test blocks were subsequently weighed
and the amount of wood eaten was estimated. Boards were then
placed in one of four categories: "S" (susceptible, 60-79 percent
termite survival), "MS" (moderately susceptible, 30-59 percent
termite survival), "MA" (moderately antitermitic, 1-29 percent
termite survival), and "A" (antitermitic, 0 percent termite
survival). The "A" group contained these species: Northern
catalpa, camphor tree, American holly, yellow poplar, osage
orange, white and red mulberry, sycamore, post oak, sassafras,
and winged and cedar elm.
c) Repellent and distasteful woods; wood
extractives as protozoacides
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Resistant woods need not be toxic, and may instead be
repellent or distasteful. Under force feeding or "no-choice"
tests with these types of woods, termites die from starvation. A
non-toxic material can also act by eliminating symbiotic
protozoa. Laboratory testing of protozoacides is preferred over
field evaluation since the former takes less time, provides more
uniform testing conditions, and allows for a more quantitative
assessment of results. Overall, laboratory tests involving wood
extractives are believed to predict reasonably well the results
of long-term field tests with the same or a closely related
termite species.
d) Extraction of resistance components
Once a resistant species is identified, solvents such as
methanol, pentane, and acetone are used to extract the components
of the wood which confer resistance. Various methods are employed
to isolate and identify the active components, although it has
sometimes proven difficult to isolate a pure sample of the
"resistance factor". Extracts are tested on filter pads for
antitermitic activity and compound identification is then pursued
using chromatographic and spectrophotometric methods. Studies are
also done to determine just how the antitermitic substance works
(for example, whether or not it targets gut protozoa).
e) Uses for antitermitic compounds derived from
wood
In the United States, the use of resistant woods in
construction has been almost totally replaced by chemical
treatment of wood. Nevertheless, investigation of the propeties
of resistant woods is still worthwhile. It is projected that
antitermitic wood extractives, in crude form or as a constituent
thereof, might be useful as wood preservatives for non-resistant
woods, as bait termiticides, or for use in soil barrier
treatments. Analogs for such purposes may also be developed.
The potential of wood extractives has been illustrated
experimentally by Carter and Deal (1982). Five inch long and one-
half inch square sapwood sticks were treated with extracts from
five woods (catalpa, holly, melaleuca, post oak, and yellow
poplar) which had proven effective as wood preservatives in
preliminary field tests. The treated sticks were inserted in
holes cut in untreated pine sapwood stakes (ten stakes per
extract) and the stakes driven into the ground. After one year,
only two of the fifty sticks showed damage that was greater than
surface nibbling. In contrast, 60 percent of the controls were
attacked.
The experiment focused on commercially important species of
American hardwoods and noted the variable nature of their
antitermitic properties. Variation has been found to exist
between trees of the same species and even within a single tree
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in which heartwood is resistant but sapwood is not (e.g. yellow ,
poplars). Further, the antitermitic component in the heartwood
may be unevenly distributed. Accurate determination of species
resistance can be made only after a large number of trees have
been sampled. In certain instances, an active extractive
component may be volatile or susceptible to chemical changes when
exposed to air. The estimated degree of resistance in woods with
these compounds therefore depends not only on the tested
termites, test conditions, and length of test period but also on
the length of time the wood has been cut prior to testing.
5. The bait block method and the use of insect growth
regulators
a) Bait block method as a viable alternative
One difficulty in killing termites, opposed to other pests,
is that their nests are often hard to locate. Even if their nests
are located and the queen is killed, supplementary reproductives
can take over and allow the colony to persist. Control through
the use of bait blocks has basically been viewed as supplemental
to more traditional approaches and has been restricted to areas
where termite pressure is low. However, since the residues of
soil termiticides are increasingly being viewed as health and
environmental hazards, the bait block technique may offer a more
viable alternative than previously expected.
b) Goal; advantages; baits; toxicants
Unlike the barrier method of control which aims at
excluding or repelling termites from certain areas, the bait
block method aims at suppressing or eliminating colonies from a
given area. Aside from the directness of its goal, the bait block
method has other advantages. First, it involves only a small
quantity of slow-acting toxicant. Second, it is not associated
with any actual or perceived environmental hazard. And third, it
does not pose the long-term threat associated with persistent
chemicals. Also, the bait block method can be employed at various
stages in the construction of a building. For example, treated
bait blocks can be placed around susceptible pine stakes in a
grid like form prior to construction to suppress the existing
termite population and lessen the termite hazard on a
construction site. Attempts to re-establish a feeding network
(destroyed by construction) would be thwarted by the bait blocks.
Perimeter baiting around a plot of susceptible stakes could be
used to intercept invading termites.
The use of baits to encourage contact with an insecticide
is a technique well-suited to social insects like termites, given
their foraging, food exchange, and grooming habits. Toxicants
used on the bait blocks include stomach poisons, protozoacides,
insect growth regulators (juvenile hormones), and combinations of
these. Some believe that use of slow-acting toxicants is the only
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feasible way to eliminate colonies of C. formosanus which may
support up to ten million individuals and maintain foraging
galleries as long as one hundred meters.
c) Mechanism
In theory, the bait block technique works as follows.
Foraging workers from a colony locate and feed selectively on a
toxic bait block. They then return to the colony and distribute
the toxicant to other colony members via trophallaxis (food
exchange). Through toxicant transfer, the colony is eventually
decimated. Field study involving C. formosanus Shiraki (Su et al
1984) has shown that individuals of this species select their
feeding sites at random. This "random selection" of feeding sites
implies that, if given enough time, all foragers from a colony
will eventually encounter a control agent that has been
introduced just at a single site, with the end result being
colony elimination. Because the bait block method relies on
preference of the toxic block over any other available food
source, the blocks are often decayed by the brown-rot fungus
Gloeophyllum trabeum. This fungus does not act as an attractant,
but it does cause workers to exhibit an arrest response (i.e.
they stop, and remain on the treated wood).
For the toxicant to perform adequately, it must be lethal,
possess minimal antifeedant properties (so as not to discourage
feeding on the toxic block), and act slowly. The latter
characteristic gives poisoned foragers time to leave the bait
block site and return to the nest, still able to poison their
nestmates. If foragers died at the bait block, not only would
spreading of the toxicant be prevented, but, as part of normal
termite behavior, contaminated individuals would be walled off
and the site subsequently avoided.
d) Testing
Initial testing of bait block toxicants involves a no-
choice test in which a series of cups containing dyed treated
cellulose and a layer of lab stone are placed within a larger
covered container. Each cup has a small hole in the bottom which
allows water to be drawn up from a moist cotton pad below.
Twenty-five R. virainicus or C. formosanus workers are introduced
into each cup. Three replicates are done for the controls and
each treatment concentration (12.5 - 5000 ppm). Test units are
examined for two weeks, with daily observations of behavior and
physical responses. Sometimes, at the end of the first and second
weeks, the number of symbiotic protozoa in the termite hindgut
are estimated for several concentrations. If the toxicant used is
an insect growth regulator, a longer period may be needed to
observe associated effects. Dead termites are removed at each
examination to minimize fungal and bacterial contamination.
Potential bait toxicants usually begin to adversely affect
termites after several days, and 100 percent mortality often
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occurs by the end of the second week.
Promising compounds are then used in choice tests in which
termites are permitted to feed on either treated or untreated
cellulose. A plastic nest unit is partially filled with a sand-
vermiculite-water mixture and two pieces of untreated pine blocks
are placed inside. The nest unit is connected to a smaller
foraging chamber by a glass or plastic tube. In the foraging
chamber is a block of fungus-decayed sweet-gum wood (Liguidambar
styraciflua L.) vacuum impregnated with the chemical being tested
(or the appropriate solvent if it is a control). Blocks are
placed in the foraging chamber twenty-four to forty-eight hours
after approximately one thousand termites are introduced. The
blocks are then covered with a thin layer of the sand-
vermiculite-water mixture and a bit of distilled water is added.
When the units are dismantled, the termites are counted according
to caste. Each bait block is cleaned of debris and dried, and its
oven-dried weight compared with the original dried weight.
Only chemical concentrations that cause significant
mortality over several weeks without exhibiting strong
antifeedant properties are considered for field tests. As long as
workers are present in the appropriate numbers, feeding should
continue. However, assessment of feeding habits when insect
growth regulators are used must be made carefully since
effectiveness of the toxicant is not strictly correlated with
decrease in weight of the toxic block. Field testing entails
placing bait blocks next to susceptible pine stakes in chosen
test plots and evaluating the damage done to the susceptible
stakes over time.
e) Juvenile hormones
The role of juvenile hormones in caste differentiation and
regulation, and the development of their structural analogs has
presented an interesting opportunity for termite control. It is
known that soldier differentiation in subterranean termite
colonies depends on the titer of juvenile hormone present at
certain times in the molting cycle of nymphs and larvae. Further,
it is believed that juvenile hormone titer and the resulting
number of soldiers are controlled by pheromones produced either
by reproductives or by soldiers. Pheromones produced by
reproductives are believed to stimulate soldier production,
whereas those produced by soldiers are believed to inhibit
soldier production.
f) Juvenile hormone analogs and their effects
Juvenile hormone analogs (JHA's) or insect growth
regulators (IGR's) are synthetic versions of natural juvenile
hormones. They can regulate the growth and reproduction of
insects and are useful in insect control programs because they
prevent proper mating and hence reproduction. Assuming no
immigration occurs, population number can be visibly reduced.
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Since mammals have different chemical growth regulators and
develop in a different manner, adverse effects on humans through
use of IGR's to control pests is unlikely. The biological
specificity and low mammalian toxicity of IGR's make them
promising components for control programs. The IGR methoprene for
example has an LD50 of over 34,000 mg/kg and has been found to be
effective for five to six years.
However, IGR's do not provide immediate kill. If quick
results are desired, insect growth regulators must be considered
as a component within a more extensive control program. The use
of IGR's is further limited by the migratory habits and life
cycles of the insect being treated. Probably the greatest concern
regarding IGR's is that they will be used in mixtures with
conventional insecticides -- an approach which will inhibit the
switch to preventative procedures and least-toxic methods of pest
control. To lessen the existing potential for development of
resistance to these IGR's, it is urged that their use be
restricted to enclosed settings, where migration of insects is
eliminated.
JHA's have a number of effects on termites. Most are
associated with the assumption of soldier or soldier-like
characteristics. Specifically, JHA's cause workers to develop
soldier-like characteristics and cause undifferentiated nymphs to
become normal presoldiers and "intercastes" (nymph-soldiers
morphologically distinct from normal presoldiers). Loss of
microbial symbionts, feeding inhibition, failure of colony
establishment by dealate pairs, and overt toxicity are other
consequences. These effects have been observed in a number of
species but responses depend on the chemical and its
concentration, the termite species, and the substrate. The most
dramatic consequence seems to be production of superfluous
presoldiers and soldiers. This occurrence causes a skewing of
caste proportions and consequently creates an energy deficit
within the colony. That is, as the number of dependent colony
members rises, fewer and fewer workers are available to care for
them. Further reduction in the number of available workers is
caused by new foragers returning to the toxic bait block. This
"snowball" effect can lead to starvation of an entire colony.
g) Examples of juvenile hormone analogs and
their consequences
Until 1983, studies primarily involved the JHA's methoprene
and hydroprene. At low concentrations (0.016 - 0.063 ppm on
filter pads), methoprene was found to cause the production of an
excess number of soldiers in laboratory colonies of R. flavipes
and R. virginicus (Banks). It also caused the loss of symbiotic
protozoa. At higher concentrations (0.125 - 2.5 ppm), methoprene
was found to be toxic. Methoprene has also been implicated as a
factor in egg mortality and female infertility. In an experiment
done by Howard (1980), unflown alates from four colonies of R.
flavipes were collected and segregated by sex. Groups of each sex
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were held separately by colony on filter paper in a darkened
incubator at about twenty-five degrees Celsius for less than
twenty-four hours. They were then exposed to direct sunlight
which induced dealation. Experimental units contained two strips
of weathered pine and a moistened sand-vermiculite matrix. The
wood had been soaked with 0, 31, or 62 ppm methoprene in acetone
and air-dried in a fume hood. One pair of dealates from the same
colony were placed in each unit. The units were sealed with
paraffin and placed in an incubator at about twenty-five degrees
Celsius. Units were checked daily for one week, and two or three
times weekly thereafter for four months. Data included the number
of eggs produced, the number of eggs hatched, and the number and
stage of larvae present. Five replicates per source colony were
used for each treatment concentration.
Within forty-eight hours, all the pairs began construction
of their nuptial cells, most near to or on top of the wood. Egg
laying started around the eighth day (except in two methoprene-
treated units in which no eggs were ever produced). The average
length of time to deposition of the first egg and the average
total number of eggs produced did not differ for the three
treatments. But, the average amount of time required for hatching
and for appearance of second- and third-stage larvae were
significantly greater in units containing the methoprene-treated
wood than in controls. Also, fewer eggs were hatched in the
treated units. It is unclear whether these effects are due to
methoprene acting as an ovicide or from its induction of
sterility in the females. Those methoprene-exposed eggs which did
hatch developed normally, although effects may have been delayed.
It is known that colonies founded by alates of R. flavipes in
wood impregnated with methoprene are less successful than
colonies founded in untreated wood. The conclusion that can be
drawn from this study is that JHA's can be used as a form of
"birth control" against infestations of R. flavipes (Kollar).
The JHA's 2-[p-(m-Fluorophenoxy)phenoxy]ethyl
ethylcarbamate (Ro 16-1295) and fenoxycarb do not exhibit the
antifeedant properties that JHA's like kinoprene, triprene,
hydroprene, and methoprene do. Jones (1984) has shown that
fenoxycarb and Ro 16-1295 cause intercaste production in C.
formosanus Shiraki and R. virginicus (Banks) . In the latter, the
number of intercastes was over 50 percent at four weeks, and
survival was significantly reduced by six weeks. Larvae and
workers had differentiated into soldier-like workers, and nymphs
had become intercastes with uneven pigmentation, misshapen wings
and abnormal mouthparts. Mandible length and head shape also
varied. At six weeks the number of intercastes in C. formosanus
also reached about 50 percent, however, significant mortality was
not achieved. It was found that differences in food substrate
altered the response of this species; intercaste development
occurred on treated wood blocks but not on treated cellulose.
6. Antibiotics used to eliminate symbiotic protozoa
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The necessity of symbiotic protozoa for cellulose digestion
in certain termites is well known. But, this relationship has not
often been exploited as a control mechanism. Experiments have
shown that elimination of just one species of protozoa from C.
formosanus Shiraki or R. flavipes (Kollar) prevents lipid
synthesis and termite survival. Aside from wood extractives and
methoprene, other chemicals such as antibiotics also cause the
loss of symbiotic protozoa. Maudlin and Rich (1980) attempted to
determine whether or not antibiotics could be used in bait
blocks. Atabrine, chloroquine phosphate, and chlortetracycline
(CTC, aureomycin) were chosen for the studies since they are
known to cause the loss of protozoa in R. flavipes workers.
The antibiotics were each vacuum impregnated into
"attractive" wood blocks or absorbent paper pads at three
concentrations (0.1 percent, 1.0 percent, and 3,0 percent) in
deionized water. In choice tests, untreated wood blocks were
readily eaten whereas feeding was inhibited on blocks treated
with atabrine and chloroquine phosphate. An inverse relationship
was found to exist between the amount of applied chemical and the
degree of feeding. Because ingestion was slight and protozoa
numbers barely affected, these two antibiotics were eliminated
from testing. Their anti-feedant properties would make them
unsuitable for use in bait blocks.
However, termites readily fed on blocks treated with CTC
even if untreated blocks were available. After two or three
weeks, protozoan numbers were quite reduced in group given 4-5 mg
CTC. It was also found that higher concentrations did not
eliminate protozoa any faster or better than lower
concentrations; the 3.0 percent concentration was less effective
than lower concentrations in choice situations. Also, the number
of Dinennympha sp. per termite was reduced after two or three
weeks at concentrations of 1 and 3 percent CTC. But, T. agilis
and Spirotrichonympha sp. persisted after three weeks. Th©
indication is that after three weeks, protozoan elimination
results in termite starvation. Controls persisted long after this
time.
In no-choice tests using 1.0 or 3.0 percent CTC and wood
blocks or filter pads, protozoa were eliminated^after three
weeks. As in choice tests, protozoan number decreased rapidly as
CTC concentration increased but a 1.0 percent solution appeared
to be adequate. Since untreated blocks present in the choice test
did not prevent the loss of protozoa, it is unlikely that forced
feeding on treated blocks in the no-choice test caused semi-
starvation. Effects observed in no-choice tests paralleled
effects known to occur when termites are given methoprene,
namely, that once the protozoa are eliminated, termites are
unable to digest cellulose and starve to death within two to
three weeks. Although survival on treated blocks was comparable
to that of controls, termites lost more weight when on the
treated blocks. The conclusion that can be drawn from this study
is that CTC is a potential bait block chemical, and that it is
more effective at lower (1.0 percent solution) concentrations
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than higher concentrations. If CTC is employed as a control,
adjustments must be made to account for dilution as it is passed
between termites by trophallaxis.
7. Liquid nitrogen as a control for drywood termites
Another alternative to conventional chemical treatment for
drywood termites was recently investigated by Charles Forbes and
Walter Ebeling (1986). It involves the use of liquid nitrogen
which, when applied to infested wood, essentially freezes
infesting termites to death. This method is advantageous for at
least two reasons. The first being that liquid nitrogen is
inexpensive and environmentally benign. The second being that
liquid nitrogen, when changed to gas upon release from the
applicator, is able to reach areas in buildings that are
inaccessible by conventional means (e.g. "drill and treat"
method). Although investigation has targeted the drywood termite,
many other insects of colonial or resticted habits are also
potential victims. Insects unlikely to escape this treatment
include carpenter ants, pharaoh ants, fire ants, plaster beetles,
psocids, bees, and possibly fleas. Other pests (e.g. powderpost
beetles) living in cabinets, panels, or floors, can be confined
by a cold-resisting, insulating tarp.
Initial testing was aimed at measuring temperatures reached
in the wooden parts of a mock-up wall, the voids of which had
been injected with liquid nitrogen. Successful results pointed to
the feasiblity of attaining lethal temperatures to control
drywood termites (Incisitermes minor). Subsequent experiments
concentrated on developing equipment and methods of application
which could be confidently employed by pest control operators.
To determine the temperature at which termites could be
killed in a reasonable amount of time, specimens were placed in
the freezer compartment of a refrigerator. Mortality figures were
derived for drywood termite nymphs and alates, and also adult
Tribolium confusum beetles. Groups of twenty insects representing
each species or stage were placed in a Petri dish on a piece of
filter paper. The temperature was measured using an Atkin
thermocouple digital thermometer. The freezer was set to approach
its lowest point (-4 degrees Fahrenheit). At -1.94 to 0.572
degrees Fahrenheit, all insects were killed within five minutes.
Testing continued with a modified mock-up wall which had
features characteristic of residential buildings. Uninsulated
areas were covered on both sides by drywall, but insulated areas
were covered by drywall on the interior and siding on the
exterior. A window was placed in the insulated area since frames
and sills are common areas of infestation. Temperatures were
again monitored with the thermocouple, but a switching device was
added to permit collection of temperature data from up to twelve
locations in the wall. Testing determined rates of application
and temperature required in the wall voids to ensure lethal
temperatures in adjoining wood members, and also the length of
time needed to maintain the flow of nitrogen to attain the
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desired temperature.
Twenty drywood termite nymphs or alates, or adult Tribolium
confusum beetles were placed in thin pyrex glass tubes and
confined to the distal portion by a wooden rod inserted into the
tube. The tube was plugged with cork and inserted into a hole
drilled into the center of a 2-by-4 inch stud. The lethal
temperature therefore had to penetrate the wood and the glass
tube before reaching the insects. (The part of the tube extending
to the outside was covered with insulation.) Temperature readings
were taken from a hole drilled into the center of the same stud
just above the insects (temperature of the insects was assumed to
be the same).
The part of the stud last to respond in both insulated and
non-insulated areas of the wall achieved the lethal temperature
in an hour and fifteen minutes or less. To reach this temperature
inside the stud, wall void temperatures did not have to fall
below -112 degrees Fahrenheit. However, since some wooden
components were large or in an effort to hasten the process,
temperatures were sometimes dropped as low as -292 degrees
Fahrenheit. Several tests showed that when temperatures in the
stud reached -4 degrees Fahrenheit, the insects were dead. Due to
the low temperatures in the wall voids, temperatures in the studs
continued to drop. The temperatures could remain at -4 degrees
Fahrenheit for over two hours even though this temperature can
kill the subjects in less than five minutes. Deliberate overkill
ensured complete elimination in all parts of the treated areas.
Further, it was found that covering the wall sections with an
insulating material increased efficiency of the process and
required use of less nitrogen over a shorter treatment period.
Insulating mats also prevented frost from forming on the outer
surface of the wall.
Field testing was carried out at two locations. The first
involved a drywood termite infestation in the outer wall of an
apartment building. Nitrogen was conducted from an outlet valve
near the building to holes drilled to the voids from the outside.
Thermocouple sensors were placed on the inside of these holes
(areas expected to be most delayed in achieving -4 degrees
Fahrenheit). Insulating mats were mot used.
Another field test was conducted involving a wall and post
of a condominium porch. Part of the post was within the wall and
extended above it. The area of the post near the wall was flanked
by two studs. Mats were laid against the treated part of the wall
and also wrapped around the exposed section of the post. For low
temperatures to reach the post's center, they had to penetrate
the studs and then the post. In thirty-two minutes, the bottom of
the post reached -20 degrees Fahrenheit, but -101.7 degrees
Fahrenheit was reached at the upper site (near the input jet) in
the same amount of time. The exposed section of the post was
treated by injecting nitrogen under the mat. The lower end
reached -15.5 degrees Fahrenheit in one hour, but by then it was
-97.2 degrees Fahrenheit in the upper site. When -4 degrees
Farenheit was reached in the lower site in the part of the post
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within the wall, the temperature stayed below -3 degrees
Fahrenheit for sixty-five minutes. The corresponding site in the
exposed post was still below -4 degrees Fahrenheit thirty minutes
after the nitrogen injection.
Research continues on improved application and equipment
mechanisms, including development of an automated metering and
timing device and an application nozzel for floors and walls. The
survival of other pests (household fleas, C.formosanus. and fire
ants) exposed to liquid nitrogen is also being evaluated.
Precautionary measures needed for this technique include shutting
off and draining water pipes, and shutting off gas pipes near the
treatment site. The effects on non-treated areas and the risks
associated with the method's application are somewhat unclear. At
this point, the application of liquid nitrogen may require an
hour or more at each infestation site. This makes the procedure
expensive compared to other methods, but with integration into
the pest control industry the cost will presumably drop.
Equipment and technical training should be available to pest
control operators in the near future.
C. Biological control of termites
1. Termites and fungi
A number of fungi and termites use cellulosic materials as
food and compete for the same nutrients. It has been shown that
wood decayed by some fungi elicits a positive feeding response,
whereas other fungus-decayed wood is toxic or repellent. One goal
of research has been to develop new approaches to termite control
with these relationships in mind. As stated earlier, the success
of bait blocks depends on the positive feeding response elicited
by termites such as R. flavipes (Kollar) to wood decayed by the
brown-rot fungus Gloeophyllum trabeum. The fungus does not act as
an "attractant" rather, when it is found by the foraging workers,
it is preferred over available non-decayed wood. Preferrence for
this type of decayed wood, after it is treated with a toxicant,
is a critical factor in determining the success of the bait block
technique. As of 1978, Amburgey (1979) cited no studies involving
development of a control technique based on negative behavioral
responses elicited by termites to non-pathogenic fungi.
2. Termite predators
Several animals feed on termites under various
circumstances, but ants are their primary predator in the United
States. It has been shown that a disturbed termite colony is
quickly invaded and attacked if ants are nearby. Yet, sometimes,
a termite colony (e.g. Reticulitermes spp.) and a fire ant colony
(Solenopsis spp.) are found coexisting in dead logs. The use of
predators for termite control, at the present, has not been
thoroughly explored. But it is known that Argentine ants
(Iridomyrex humilis), common in California and the southern areas
of the United States, can kill a large number of termites
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overnight. Subterranean termite shelter tubes normally provide
protection from these invaders as long as they remain intact. It
is when swarming termites have just emerged from the soil, just
landed at a new colony site, or during the early stages of colony
establishment that they are most vulnerable to ant attack.
Insecticides regularly applied at foundations of buildings
against predaceous ants negate a rather effective and natural
form of termite control.
3» Termite parasites
a) Nematodes vs termites
Some groups of nematodes (round worms) are specific to
insects and do not harm plants, animals, or microbes. Spear™, a
mixture of predaceous nematodes, is a commercial product that is
applied to infested soil or wood as a water solution in the same
way that conventional termiticides are. The nematodes can, over
the span of a few inches, seek out the termites, enter their
bodies, and kill them. Because termites feed on their dead or
dying nestmates and also share food and feces, parasitic
nematodes can quickly circulate throughout a termite colony and
destroy part or all of it.
The entomogenous nematode Steinernema feltiae Filipjev
(Neoplectana carpocapsae Weiser) has been investigated as a
control for R. tibialis (Banks) in both laboratory and field
situations. This species of termite is widespread from the
deserts of California to Illinois, and up to Montana. It is
similar in habit to R. hesperus Banks and to R. flavipes (Kollar)
and is found in dry areas. It is responsible for less damage than
other species simply because fewer opportunities to attack
buildings exist in its normal habitat. R. tibialis feeds on
native and structural wood and is often found in herbivore dung.
Laboratory trials suggest that the following species are also
susceptible to this nematode: C. formosanus Shiraki, Nasutitermes
costalis Holmgien, Zootermopsis sp., and other Reticulitermes
species.
Researchers at the University of Hawaii, working with
laboratory termite colonies, have found that elimination of
colonies is possible with nematodes. But, they have also found
that infected individuals, when introduced into a colony, are
quickly walled off and cease to be effective parasite carriers.
Epsky and Capinera (1988) determined the laboratory efficacy of
S. feltiae against R. tibialis by setting baited traps in areas
where the termites foraged. Each trap consisted of a wood-strip
frame and a cloth floor plus two pieces of moistened laminated
cardboard as bait. Twenty-five out of the twenty-nine traps set
were attacked. Whether or not termites attacking the traps came
from the same colony was not determined, but the choice of well-
spaced colonies insured that many separate colonies were
evaluated.
In laboratory tests, field-collected termites were placed
in Petri dishes with tight-fitting lids, each containing a
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section of 4 percent agar with a piece of sweetgum wood
(Liquidambar sp.). LD50 estimates were made using Petri dishes
containing two pieces of filter paper and ten termites. Doses of
0, 100, 3,200, 10,000, and 100,000 nematodes along with 1 ml
formalin (0.1 percent) were applied to each dish. Five replicates
per concentration were done, using termites from different traps
in each one. Termite mortality was recorded at thirty-six, sixty,
and eighty-four hours after inoculation. Testing confirmed the
susceptibility of R. tibialis to S. feltiae and showed that
termites exposed to the second dose were all dead within eighty-
four hours.
Additional trials utilized a substrate of wood chips in 4
percent agar to assay termite mortality in choice tests and to
determine termite avoidance of nematodes. The experimental setup
included three plastic cups connected by plastic straws. In the
first trial, two hundred nematodes in 1 ml formalin were added to
the right or left cup in each behavior arena. The other cup was
supplied with 0.1 ml formalin but no parasites. Ten workers were
then placed in the center cup and allowed to choose between the
nematode-filled and nematode-free cups. In the second choice
trial, zero and ten thousand nematodes (each in 0.5 ml formalin)
were used, and ten termites were added. The number of termites
and their location in each of the arenas were recorded for one
week. Avoidance was said to be indicated by feeding in the
nematode-free cups. Little mortality occurred in choice tests
with ten nematodes per termite (trial one) , but 100 percent
mortality occurred in choice tests when five hundred nematodes
were given per termite (trial two) within three days. It was also
noted that termites fed little in the paper-Petri dish assay as
opposed to the agar substrate assays in which they actively
tunneled and chewed the agar, increasing the chance of infection.
In the no-choice test, substrate was added to all three
cups and twenty workers were added to the middle cup. After one
week, termite location was recorded. Either zero or two thousand
nematodes in 0.25 ml formalin were added to the cup where most of
the nematodes were. Movement out of the original location
(indication of avoidance behavior) and the number of termites
surviving after one week were recorded for each of the twenty-
three behavior arenas. In the arenas with one hundred nematodes
per termite 58.2 percent mortality was found. Other studies
achieved 98 percent mortality with two hundred nematodes per
termite and 100 percent mortality if 133 nematodes were given per
termite. Termites did not avoid nematode-infested areas in either
choice or no-choice trials.
In field tests, nematodes were applied at a rate of IxlO7
per square meter to soil below termite traps and termites were
counted at three subsequent samplings. Results showed that the
baits could only be protected for two to three weeks at the
applied nematode rate. Untreated traps generally had numerous
entrance holes and a network of tunnels. Many termites were found
under the traps. In contrast, termites attacking treated traps
the corner or went around the frame and attacked the
-K
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top. The undersides had few holes and hardly any termites were
found underneath these traps.
This experiment confirmed the termite's susceptibility to
the nematode but also illustrated the fact that termites avoid
areas with large numbers of nematodes or try to exploit small
gaps in nematode-covered areas to reach a food source. The
potential for reinvasion by termites suggests that it may be more
effective to treat the whole colony rather than just the feeding
site and hence eliminate the need for frequent nematode
application.
Colony extermination has been obtained in studies on the
live-wood tea termite Glyptotermes dilatatus with Heterorhabditis
sp. These termites behave like wood-boring beetles and are able
to live inside wood with little or no connection to the ground.
Although these subjects are very different from subterranean
termites, a chain of infection similar to that seen in the study
could provide a way to eliminate subterranean termites. Research
regarding other strains of S. feltiae (or other nematodes) and
application methods required for long-term protection need to be
pursued.
b) Controversy
Olkowski's update (1985) indicates that the use of
nematodes in commercial applications has met with mixed success.
Stan Post and Bob Drucker head the company N-Viro which
distributes SAF-T-SHIELD™, a product containing the parasitic
nematode N. carpocapsae, strain forty-two. The parasites are sold
in units of four million at a cost of thirty-nine to fifty
dollars. Post has treated four thousand stuctures since the
spring of 1984 and believes that the nematodes are helpful in
controlling termites in residential areas. The company's success
rate is estimated to be 80 percent (not far from the 92 percent
maximum given for chlordane). The estimate is based on the number
of re-treatments and reports from other pest control buyers. It
is expected that increased operator training will raise the
effectiveness level. The dosage relationship between different
soils and the,, quantity of nematodes must still be determined, as
must the routineness of the treatment.
Another pest control operator says he regularly injects
nematodes under concrete-slab foundations to treat existing
termites and finds the technique 95-100 percent effective. Still
another company reports that they are achieving 50 percent
effectiveness with initial treatments. The indication seems to be
that follow-ups are necessary, particularly when preventative
modifications have not been made. Initial treatment results are
expected to improve once a way to help the nematodes withstand
drying has been developed.
Ironically, it is precisely this short-lived characteristic
that makes nematodes such an appealing prospect for termite
control. Unlike conventional long-lived insecticides, nematodes
can survive for only two years, depending on the availability of
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moisture. While this ensures that no harmful residues remain in
treated areas, it also makes monitoring more crucial, especially
where re-treatment is concerned.
Some negative conclusions on nematode use have been drawn
by the media in response to research results obtained by Raymond
Beal at the Wood Products Insect Laboratory of the U.S. Forest
Service in Gulfport, Mississippi. Field tests, performed in much
the same way as for conventional insecticides, were used to
evaluate nematode effectiveness against termites. Field plots
were covered with eight to forty thousand nematodes per square
foot. A pine board was then placed over treated areas, covered
with a black polyethylene vapor barrier, and held in place with a
concrete slab. After one and two months exposure, Beal calculated
the percentage of damage.
George Poinar, an insect pathologist at the University of
California at Berkley, was asked to comment on the media's
conclusions and cited several aspects of the study which he found
problematic. One is that the field site contained what could be
considered an unlimited supply of termites. As the nematodes
killed termites, other termites moved in and continued to feed
until the nematodes were used up. (The nematodes were basically
"outnumbered".) Poinar does not consider the field site typical
of most residential infestations and thinks that the results of
the study are somewhat of a testament to the usefulness of
nematodes. He also points out that the strain of nematodes used
in the Beal study was not the one (strain twenty) that is
commercially distributed. Poinar concludes that the Beal study
should not be considered indicative of the potential use of
nematodes and that negative publicity, the large investments made
in conventional methods, and a general unwillingness to change
will delay appropriate investigations. It should be noted that
Beal has stated that his work was preliminary and that
conclusions from the study should be drawn carefully -
Fortunately, some pest control operators have forged ahead.
Obviously, communication between pest control operators and
researchers could help in the development of suitable uses for
nematodes and ease the transition of this and other control
techniques into industry.
4. Termite pathogens
Research has involved pathogenic fungi and bacteria as
possible methods of control. Several patents are involved with
pathogenic bacteria, but their practical value is questionable.
D. Physical methods of termite control
1. Use of extreme heat
The susceptibility of insects to high temperatures has also
been exploited as a means of control. Using thermostatically-
controlled temperature cabinets, Charles F. Forbes and Walter
Ebeling (1987) have determined the amount of time required to
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32
achieve 100 percent mortality of adult male German cockroaches
Blatella gentianica. adult flour beetles Tribolium confusum,
nymphs of the western drywood termite Incisitermes spp., and
adult Argentine ants Iridiomyrmex humilis, at 115, 120, 125, and
130 degrees Fahrenheit. The least amount of time required for 100
percent mortality was found when the temperature was increased
from 115 to 120 degrees Fahrenheit.
Another experiment by these researchers determined the
amount of time needed to reach 115, 120, and 130 degrees
Fahrenheit in a block of Douglas fir (3.25-by-1.50 inches in
cross-section and 4 inches in length). Temperatures were
determined via thermocouple sensors set within the center of the
wood block. Tests were also done using a larger block at 160
degrees Fahrenheit. Drywood termites nymphs were placed in the
centers of the blocks in an effort to simulate treatment of
structural infestations. The emphasis was on attaining lethal
temperatures within a practical time span.
A small mock up house was used to see how long it would
take for lethal temperatures to be reached inside various wooden
members. The house included components found in conventional
residential construction such as 2-by-4 inch studs, 4-by-12 inch
headers, and 6-by-12 inch beams. A crawl space, attic, ceiling
joists, and wall voids with and without insulation were also
included. Air from an electrically-driven blower was passed
through a gas-filled heater and into the house through an
eighteen inch insulated flexible metal duct. Heated air was drawn
out through a similar duct at the opposite end of the house and
recycled back into the blower. Heating efficiency was increased
by covering the roof with tar paper and wrapping the entire house
with a black plastic tarp. The latter ensured that lethal
temperatures were maintained in the outer surfaces of the house.
Temperatures were monitored in twelve locations per treatment via
thermocouples. Temperature curves were determined for various
locations in the house, and the room temperture was not raised
above 180 degrees Fahrenheit.
In another test, the room temperature was not raised above
160 degrees Fahrenheit and a quarter-inch tunnel was drilled into
the center of a 2-by-4 inch ceiling joist. Drywood termite nymphs
and flour beetles were placed in the bottom and the tunnel packed
with fiberglass insulation. It was found that a half-hour at 120
degrees Fahrenheit was sufficient to kill the insects. Similarly,
two hundred German cockroach nymphs, twenty adult flour beetles,
and numerous cat flea (Ctencephalides felis) larvae, pupae, pre-
adults, and adults were confined in the plastic containers and
placed in the house. All were dead after thirty minutes at 120
degrees Fahrenheit. Compared to free-living house-hold pest,
wood-inhabiting pests are somewhat protected in their chambers
and require more time to be killed by higher temperatures.
A smaller, lighter heating device was used in field tests.
Five treatments of drywood termites and one of carpenter ants
were performed. In the second story of a two story condominium,
two bedroom-living room units with termite-infested ceiling beams
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33
were treated. A bathroom through which alates had entered was
also treated. All three rooms were accessible by balconies and
the heater was carried to each of these sites. Propane gas was
conducted to the heater by a hose from a tank situated on the
ground below. Access to the bathroom was attained by means of a
duct pulled in from one of the bedrooms. A hole was drilled to
the center of a ceiling beam in each room and a sensor was
inserted before the hole was packed with insulation. In the first
treated room, 120 degrees Fahrenheit was reached in fifty-three
minutes in the ceiling beam.
In another case, a 4-by-6 inch termite-infested beam in a
second story balcony was treated. A plastic tarp was placed over
the balcony and loosely held down with duct tape. A flexible duct
brought heat from the ground-level heater to the balcony. The
temperature under the tarp rose from seventy-four degrees
Fahrenheit to 140 degrees Fahrenheit in six minutes, with the
beam center temperature reaching 120 degrees Fahrenheit in
seventy-six minutes.
One treatment involved carpenter ants (Camponotus
clarithorax) which had infested a kitchen-breakfast-utility room
area for ten years. At this site, the duct was directed for hot
air discharge along the floor, thereby avoiding the
stratification of heat that had been noted in earlier
experiments. A sensor was placed in the center of a 2-by-4 inch
stud under the sink cabinet. To reach the stud center, heat had
to penetrate 3/8 inch plywood and then the stud itself. In three
hours 120 degrees Fahrenheit was achieved. No workers or alates
have since been found in this treated area.
In all the heat treatments done by the reasearchers for
drywood termites, a good deal of "overkill" was aimed at
presuming that areas difficult to reach would be adequately
exposed. All visible fecal pellets had been removed prior to the
treatments and no new pellets have been seen since. There was no
damage detected to usual house furnishings or their contents,
except for candles which melted when* temperatures at certain
times rose to 130 degrees Fahrenheit. Thin plastic containers and
similar items were found to become somewhat distorted. It was
also found that heat applied to only one side of a door caused
the door to warp (i.e. a concave surface resulted on the heat-
exposed side). Normal shape was regained upon cooling,
A full-scale treatment was done on a two bedroom house
infested with powderpost termites (Cryptotermes brevis). The
house was covered with a tarp as done for fumigations, and the
heat discharged from the machine through the front door. The
attic was not insulated and the access hole to the attic from the
hallway was left open. Temperatures were again monitoered via
sensors inserted into various wood members. Attic and living
space temperatures were also monitored. Lethal temperatures of
125 degrees Fahrenheit or more were reached in two hours in all
the areas where the sensors had been placed.
2. Sand barriers for control of subterranean termites
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The use of sand or crushed volcanic cinders as a barrier to
R. hesperus was proposed by Ebeling and Pence in 1957. At that
time, it was observed that termites construct tunnels at the rate
of about an inch per hour. They do this by pushing their head
forward in the sand and by using their head and mandibles to
press the sand particles to either side of the tunnel. Smaller
particles are taken in their buccal cavities and placed along
tunnel walls to form a smooth and tightly sealed surface. A spot
of fecal "cement" is put down before particles are set. Termites
use their broad hypopharynx (tongue) for pushing particles and
for spreading sand, earth, and fecal material. To build above-
ground shelter tubes, termites carry small sand and soil
particles in their buccal cavities and grasp larger ones in their
mandibles. Their mandibles have a span of only 0.5 mm, but by
grasping an edge termites can move particles up to 1 mm in size.
Recently, experimentation has been pursued and a patent
applied for by Ebeling and Forbes (1988). This seemingly
simplistic type of control targets termite tunneling and tube-
building behavior by substituting a penetrable medium with an
impenetrable one in areas through which termites are likely to be
moving. An indirect advantage is that the sand helps to absorb
dampness in termite-prone areas.
The 1957 study showed, and recent studies confirm, that
fine dry sand cannot support subterranean termite galleries.
Specifically, it has been shown that R, hesperus nymphs are
unable to penetrate a layer of dry or moist sand consisting of
particles ranging in size from 2.5 to 1.6 mm (ten to sixteen
mesh). (Note: high mesh number means mesh openings are smaller
and that fewer large particles are accepted.) The smallest
particles in this mixture are too large for the termites to move
aside and the largest ones cannot be crawled around. The mixture
is still effective even if larger particles (six to sixteen mesh)
are added, as long as the barrier is tamped to remove penetrable
spaces. Nymphs are able to penetrate dry or moist grit, or
particles 3 mm in diameter. They can also tunnel through fine
moist sand.
To successfully implement this sort of control, sand must
be of the reguired range, be used industrially, and be available
commercially. The sixteen or twelve (mesh) sand used in sand
blasting is acceptable and inexpensive (about four dollars for a
hundred pound sack). A sample of twelve grit sand has the
following composition: 71.4 percent ten to sixteen mesh, 9.5
percent larger than ten mesh, and 18.5 percent smaller than
sixteen mesh.
At the USDA Southern Forest Experiment Station, Susan Jones
performed various tests with the aggressive tunneler C.
formosanus. Using groups of about 750 workers and soldiers, Jones
found that the termites could penetrate a three-fourths inch
layer of dry twelve grit in six days; in three days if it was
moistened. Dry sixteen grit was penetrated in twenty-four hours.
These experiments indicated that particles smaller than 16 mesh
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35
should be removed from a mixture unless their percent in the
composition is small and the barrier is tamped to prevent
penetration.
Sand barriers can be applied in the crawl spaces inside or
outside a foundation's perimeter. Since laboratory tests proved
that a sand-concrete barrier can resist violent shaking, these
barriers could be used in crawl space construction to seal earth-
filled porches, patios, and steps from the foundation, and could
also be used to repair similar barrier interfaces which have been
disrupted. A six to sixteen mesh sand used in these cases would
have to be tamped to ensure removal of penetrable spaces. In
slab-on-ground construction, the sand would have to be applied
before the concrete is poured and may need to include a layer of
gravel to weigh down the sand or cinder barrier.
In a recent field test, a crawl space under the residence
of a chemically-sensitive person was provided with a sand
barrier. The infestation had originated on the outside and had
reached wood via tubes stretching from below the ground through
loose stucco, to the sill, and then to cripples, joists,
flooring, and studs. A concrete termite barrier six inches wide
and eight inches deep had been installed when the house was
built. It encircled the foundation but had been separated from it
in certain areas due to foundation movement. This barrier was
removed, and enough concrete was poured into the resultant trench
to hold an eight inch wide strip of metal flashing three inches
from the foundation. Twelve grit sand was poured between the
flashing and the foundation to a depth of seven inches. Pouring
the sand to within a half inch of the top of the flashing was
expected to prevent roots that penetrated the concrete from going
any further in providing termite access. Salt (also a termite
barrier) was sprinkled in the lower part of the sand barrier to
combat potential breaks between the concrete and the foundation.
The refilled trench was covered with a cap of concrete. Results
have been successful. Movement into the substucture has ceased
and no new infestations have been found.
Generally, the formation of a sand barrier outside a
foundation is a simpler process and suitable for both crawl space
and slab-on-ground types of construction. In one treated area, a
compressor (able to hold 250 pounds of sand) was connected to a
fifty foot long tube one inch in diameter, and used to blow sand
into a crawl space. Three hundred pounds of sand were blown from
the hose at the rate of one cubic foot per five minutes to create
a barrier one inch deep and covering an area twenty inches wide
by twenty-four feet long. The sand was tamped with a brick to
increase efficacy of the barrier. The whole process took about
seventeen minutes.
3. Digging up subterranean termites
One type of physical control that can be exerted on
subterranean termites is simply digging up small colonies. Even
if all the termites are not removed in this process, digging
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36
breaks apart the nest and exposes remaining termites to attack by
natural predators such as ants. Regular monitoring of these sites
is recommended, as more digging out may be necessary. Shelter
tubes can be broken easily or removed entirely to destroy the
connection between soil and wood and further increase the
probability of natural-enemy attack.
4. Termite control by electromagnetic devices
Electromagnetic devices were once sold as preventative and
remedial controls for termites. However, tests conducted by the
Forestry Sciences Laboratory in Gulfport, Mississippi showed that
they were ineffective. The EPA issued a "stop sale" on the
devices since manufacturer claims were not substantiated. Three
different devices were tested and field tests with subterranean
termites exposed to the mechanisms for six months showed no
significant change in tubing behavior or in frequency of attack.
In lab tests with drywood termites, no significant differences
were found in mortality, amount of wood consumed, or increase in
termite biomass after three months exposure.
5. Electrogun™
A new approach to elimination of drywood termites is use of
the Electrogun M The device is an AC pulsing generator that
operates on a low current (90 watts), high voltage (90,000
volts), and high frequency (100 kHz). It aims at killing the
insects in their galleries. The unit is safe for the operator to
use and emits no harmful radiation (e.g. microwaves, x-rays,
ultraviolet rays). The inventor of the device, Dr. L.G. Lawrence,
made use of the fact that drywood termites frequently create
galleries just below the surface of the wood. Access to the
termites can also be gained through their "kick holes". Holes can
also be drilled directly in the wood or a nail inserted to carry
the current inside. Studies have shown that the current
recommended can travel down half an inch and kill termites
existing there.
The "Extermax System" (i.e. the name of the process using
the gun) was tested by Dr. Walter Ebeling. Two hours post-
treatment, moribund termites were dissected to determine the
condition of their symbiotic protozoa. All protozoa in treated
termites were found to be dead, while those in untreated controls
were still alive. Five days later, treated termites also died.
This lag time, between treatment and death, is characteristic of
the technique but the exact cause of termite death is not clear.
It is probably connected with the loss of symbiotic protozoa.
Dr- Ebeling has observed the technique performed and states
that the technician moves a probe rapidly over the infested area,
stopping at galleries near the surface when the current's sound
and appearance dictate it. From treated points, the current can
flow eighteen inches, but probes cannot be pushed too far into
the kick holes because the current will carbonize a path directly
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to the electrode, diverting it from the termite gallery-
Of the thirty-five Electrogun™-treated infestations
followed by Dr. Ebeling, only three required follow-up treatment.
In a questionnaire, eight out of nine operators said that they
received fewer call-backs with this treatment than with the
"drill-and-treat" method using conventional insecticides. One
operator has found that with increased operator experience, call-
back number has dropped. (One call-back was traced to aluminum-
backed insulation that had interfered with the process.) Another
operator says he has completed over $400,000 in business with the
gun and offers a two year unconditional guarantee. The potential,
he believes, is limited only by operator expertise. The
Electrogun™ is distributed nation-wide and training is provided
by the distributors. Research has been underway to adapt the tool
to control of ground-dwelling insects such as subterranean
termites and fire ants, but devices for this purpose were not on
the market as of 1984.
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BIBLIOGRAPHY
Amburgey, Terry L. "Review and Checklist of the Literature on
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Carter, Fairie Lyn and Raymond H. Beal. "Termite Response to
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Insecticidal Dusts." Common Sense Pest Control Quarterly III
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ANTS
I. Carpenter ants
A. Identification of problem
1. Introduction
2. Carpenter ants: in their natural environment and as
pests
B. Carpenter ant biology
1. Colony organization
2. Nesting habits
3. Food sources
C. Carpenter ant detection
1. Distinguishing from termites
2. Appearance of infested wood
3. Professional inspections
D. Carpenter ant prevention
1. Introduction
2. Removal of attracting conditions
E. Carpenter ant control
1. Chemical control of carpenter ants
a. Conventional insecticides
b. Desiccating dusts
2. Biological control of carpenter ants
3. Physical control of carpenter ants
a. Electrogun™
b. Removal of nest, damaged wood, and strays
II. Other pestiferous ants
A. Identification of problem
1. Introduction
2. Ants in their natural environment
3. Ants as pests
B. Pharaoh ant and Argentine ant biology
1. Pharaoh ant
2. Argentine ant
C. Ant detection
D. Ant prevention
1. Introduction
2. Elimination of food sources
a. Food storage containers
b. Management of wastes
3. Permanent sticky barriers
4. Modification of habitat
E. Ant control
1. Chemical control of ants
a. Dusts
b. Silica gel-pyrethrum combination
c. Insecticidal soap
d. Boric acid baits
e. Insect growth regulators
2. Biological control of ants
a. Pyemote mite
b. Nematodes
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c. Coordinating colony cycle with treatment
d. Disturbance of feeding trails
Physical control of ants
a. Detergent barriers
b. Flooding
c. Temperature extremes
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ANTS
I. Carpenter ants
A. Identification of problem
1. Introduction
There are five hundred species of carpenter ants (genus
Camponotus) but only nine species are common in the United
States. Secondary data derived from Cooperative Extension Service
(C.E.S.) entomologists in several northeastern states indicate
that carpenter ants are displacing subterranean termites as a
primary concern of the general public. Fowler (1983) reached this
conclusion assuming that the number of inquiries received by the
C.E.S. was a function of the sighting incidence by the general
public.
New Jersey C.E.S. data on structural pests shows that, in
terms of total number of queries, carpenter ants, subterranean
termites, wasps, and other ants all ranked higher than
cockroaches (the most prevalent structural pest). This seems to
point to a bias on the public's part towards concern over
wood-damaging social insects versus more common pests such as
cockroaches. The switch in queries began around 1960 and can be
partially attributed to changes in weather, settlement patterns,
and human awareness. Suburbanization increased the risk of
structural pest attack in homes, but widespread and effective use
of chlordane as a soil termiticide decreased the rate of
subterranean termite infestations in relation to that of
carpenter ants. This combination of events has apparently
heightened the public's concern regarding potential carpenter ant
problems.
2. Carpenter ants: in their natural environment and as
pests
In their natural habitat, carpenter ants live in logs,
stumps, and hollow trees and act as decomposers of decaying wood.
They become a problem to humans when they enter wooden buildings
and cause structural damage. Although long-standing infestations
may require extensive repairs, minor repairs (if any at all) are
most frequently necessary. Carpenter ants are important pests in
the Northwest and the Northeast, and it has been estimated that
several million dollars are spent yearly, particularly by the
urban public, on control measures. Although worker ants will bite
if provoked, it is their rather large size that seems to be of
greatest annoyance. Once established indoors, carpenter ants
behave like other house-invading ants in their search for food.
B, Carpenter ant biology
1. Colony organization
Carpenter ants, like termites, are colonial insects which
mine in wood. Ant eggs hatch into white, soft-bodied, helpless
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larvae which pass through a number of growth stages prior to
pupation and adulthood. Most larvae develop into workers
(foragers) which support the queen and developing young. Adults
are most often black, but they may be reddish-brown or yellow in
color. There are three adult castes: worker, winged male, and
winged female.
Workers vary in size from 5/16 to 7/16 of an inch, and are
divided into two groups -- majors and minors. Majors are
sexually-underdeveloped females which guard the nest and forage
for food, transferring it to the smaller workers (minors). Minors
expand the nest and care for the young.
Winged males (kings) develop from unfertilized eggs and are
about 7/16 of an inch in size. Winged females (queens) develop
from fertilized eggs laid by mated queens and are 3/4 of an inch
long. Between spring and mid-summer, winged reproductives emerge
from the mother colony to mate. Males die soon thereafter, but
females shed their wings and establish new nest sites. Each queen
excavates a small cavity in wood, seals herself in, and lays
fifteen to twenty eggs. She feeds her young with mouth fluids
derived from stored fat and metabolic conversion nutrients of her
wing muscles. The first workers produced by the queen are small
since they were nourished by her reserves, but when they mature
they are responsible for tending to the next brood and expanding
the nest. This allows the queen to devote all her energies to
egg-laying. Although in most species there is only one queen per
colony, each queen is able to lay thousands of eggs over what can
be a fifteen year life span.
2. Nesting habits
Colonies reach a peak population size in three to six
years, with worker number about three thousand. At that time
winged reproductives are produced and new colonies set up, either
by a single fertilized female or by movement of colony members
through "budding". In the latter process, scouts establish small
satellite colonies in firewood, lumber, and wood debris, in or
near buildings. Budding is considered the main mechanism behind
house invasion. In a study conducted in urban areas of New
Jersey, carpenter ants were seen in 75 percent of the 306 shade
trees examined. Each colony kept their brood in one tree, but it
was found that a number of auxiliary sites, joined by underground
tunnels, existed in other trees.
It is possible that destruction of forested areas may cause
the ants to seek out nearby buildings. Carpenter ants attack both
hard and soft wood, often selecting out partially-decayed areas.
It has been found that black carpenter ants cannot inhabit wood
with a moisture content level below 15 percent, although colonies
can be established in wall voids or cavities within a structure
and sometimes even in the open. Nests usually start out in damp,
somewhat decayed wood but later expand into dry wood. They need
not be located inside an infested structure, and may instead be
found in a hollow tree or stump located adjacent to the house,
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with ants entering the building through openings in the
foundation. Colony members hibernate in the winter, unless the
nest is in a warm part of the building. It is possible for all or
part of a colony to move to a new site.
3. Food sources
"Honeydew" from aphids, leaf-hoppers, mealybugs, scales and
white-flies is the primary food of carpenter ants. They also eat
dead insects, plant and fruit juices, sweets, meat, grease, and
fat. Workers can exist for six months without food and if under
stress the queen and a few workers can persist through
cannibalism.
C. Carpenter ant detection
1. Distinguishing from termites
Because correct identification of invading insects is
directly related to the effectiveness of control measures,
differences between swarming termites and carpenter ants should
again be noted. Regarding morphology, carpenter ants have narrow
waists and "elbowed" antennae, whereas termites have broad waists
and slightly concave antennae. Behaviorally, carpenter ants use
wood to construct their nests and to reach water and foodstuffs,
but they do not eat the wood like termites do. Wingless adult
carpenter ants can be found foraging for sweets or protein inside
the house, their presence most noted in kitchens and other areas
providing food and water between the hours of 11 and 2 pm. In
contrast, termites need not leave the wood that they infest since
it provides most of their resources.
2. Appearance of infested wood
Carpenter ant nests within a structure may be marked by
slit like entrances or "windows" covered with a clear material
made by the ants. Existing cracks and crevices can also be used
as entranceways. Generally, wood shavings and frass (insect
feces) will be seen just beneath an entrance. This "sawdust" may
also be seen sifting from cracks in siding, behind moldings, in
basements, and under porches. If the infestation is an active
one, the shavings will be in the form of chips, the frass will be
dark and square-ended, and there may be parts of or whole dead
ants present in the debris. Carpenter ant tunnels are
characteristically cut against the grain of the wood and are
smoothly polished and free of wood shavings, soil, and fecal
pellets. Invading ants make a rustling noise in the walls (this
increases if you knock on the wall because the ants are sensitive
to vibrations).
3. Professional inspections
As stated in the section on termite detection, beagle dogs
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are being used during professional inspections. It is possible
that these dogs could also be trained to locate carpenter ant
infestations. The expectation is that they would significantly
improve the reliability of inspections and that this would lower
the number of fumigations and facilitate spot treatment
procedures.
D. Carpenter ant prevention
1. Introduction
Once it has been decided that treatment for the ants is
required, a qualified person can be enlisted to follow the most
effective, least-toxic route. Again, an educated consumer is a
vital factor in the success of the chosen program. Monitoring
before and after treatments is also critical since it measures
the effectiveness of the control procedure. Because termites and
carpenter ants are similar structural pests, recommended
preventative and direct control measures are nearly identical
under a least-toxic management program. To avoid repetition, I
have simply highlighted certain aspects of the techniques
previously discussed under termites.
2. Removal of attractive conditions
The first and most important step in prevention is to
remove the conditions which are causing wood to become and remain
damp; the construction practices previously outlined do a great
deal in eliminating and preventing water retention around the
home. Nonetheless, areas wetted by poor ventilation, leaky roofs,
or roof gutter overflow are typical places to check for carpenter
ants. Commonly tunneled wood includes porch pillars and
supporting timbers, sills, girders, joists, studs, and window and
door casings. Damaged wood should be replaced or repaired, and
suspected wood should be probed with a screw driver or ice pick
to see if it gives way under pressure. If ants appear, the nest
has probably been located. Another way to prevent infestation is
to remove firewood, stumps, and waste wood from around the home.
Trees should be pruned so that they do not touch the building and
provide an easy accessway for invading ants.
E. Carpenter ant control
1. Chemical control of carpenter ants
a. Conventional insecticides
Partial control of carpenter ants can be achieved through
application of ant-roach aerosols or the residual insecticide
malathion to areas encountered by the ants. The central factor in
elimination of carpenter ant infestations aside from location of
the nest and destruction of the colony, is elimination of the
queen. Unfortunately, chemical controls are often used as a
substitute for needed structural change and habitat modification;
economic concerns are most often stated as the reason for a
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traditional approach.
b. Desiccating dusts
As with termites, desiccating dusts can be a major
component of carpenter ant prevention. Both diatomaceous earth
and silica gels are used, but boric acid dust is also effective.
Boric acid is derived from borax and is non-volatile once in
place. (That is, it does not enter the air and present a
respiratory hazard.) It is applied as a light film which adheres
to insects and is ingested by them during grooming. Boric acid
dusts are most effective when kept dry, and can last for the life
of the building in which it is applied. The best formulations
include the following: an electrical charge to increase adherence
to the target, an anti-caking compound, and blue coloring and a
bitter taste to prevent ingestion by humans and pets. Boric acid
dusts are manufactured primarily for use against cockroaches and
a more detailed treatment is given in that section.
Special application tools are needed for applying this
chemical in wall voids. Even small amounts of boric acid are
poisonous if eaten by children or pets, so excess should be kept
in sealed out-of-reach containers. During application, the
material should not be inhaled or allowed to enter the eyes, and
treated areas should be posted to prevent accidents. Baits and
broadcast liquid formulations of carbamates and organophosphates
insecticides are also available for the control of carpenter
ants. If a choice exists between the two, baits are better since
there is less exposure to the material.
2. Biological control of carpenter ants
Researchers at the Bio-Integral Research Center (editors of
Common Sense Pest Control Quarterly and The IPM Practitioner)
have found, in a pilot field test, that nematodes are effective
at eliminating carpenter ant colonies. Although the technique
needs to be perfected, it is predicted that nematodes can be used
effectively against this insect, without presenting a hazard to
resident of the structure. The researchers advise mixing a few
teaspoonsful of the nematodes with a protein substance such as
tuna fish or pet food, and placing the mixture where the ants
will find it. Pre-baiting (i.e. without the nematodes) will
establish how attractive the chosen bait is and will prevent
wasting the nematodes. Sugary substances can also be used as
baits but it is more likely that nematodes carried by a
proteinaceous bait will reach the developing larvae and
reproductives.
3. Physical control of carpenter ants
a. Electrogun™
The Electrogun™, as described under the discussion for
physical control: of termites, is also a useful tool for the
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control of carpenter ants.
b. Removal of nest, damaged wood, and strays
It is crucial to find where the nest is, then to remove
damaged wood, the nest, and any strays. It is also important to
remember that these ants sometimes nest in wall voids rather than
the wood itself, and that a discovered nest may not be the
primary one. If the ants in one area are eliminated, and the
access points caulked, then it is probable that the infestation
has been eliminated, at least in that area. When handling small
infestations, a large sponge, saturated with a sugar solution can
act as a trap. Once the ants have collected in the trap, they can
be killed by sinking the sponge in a bucket of soapy water.
II. Other pestiferous ants
A. Identification of Problem
1. Introduction
Ants are numerically the most abundant social insects.
There are between 12,000 and 14,00 species, but only 7,600 (in
250 genera) have been described. In North America, 455 species
are found. The major house-invaders include: the thief ant
(Solenopsis molesta), the little black ant (Monomorium minimum),
the odorous house ant (Tapinoma sessile), the pharaoh ant
fMonomorium pharaoni), and the Argentine ant (Iridomyrmex
humilis). The last two species will be discussed here.
2. Ants in their natural environment
In their natural environment, ants prey upon a number of
insects including certain household pests such as the silverfish
and clothes moth. The Argentine ant for example attacks
subterranean termites, and also helps aerate hard, dry earth and
recycle dead plant and animal material. Ants living in the house
help to clean up tiny debris particles — potential food for even
more pestiferous insects. These "pests" are therefore beneficial
cleansers and fertilizers, even when not in their natural
environment. Species that enter the home generally do not sting,
and the ones that bite are not aggressive. Populations of species
that regularly nest in the home are not likely to become large if
habitat modification and basic controls are maintained.
3. Ants as pests
However, when ants invade the home in search of a meal,
they often present a problem. Largely it is an aesthetic one
since their presence is thought to reflect poor house-keeping
practices. Regular house invaders such as the thief ant, pharaoh
ant, or Argentine ant are not usually carriers of pathogenic
agents, but foods that they have swarmed over should be disposed
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of since it can be assumed that they carry organisms which cause
spoilage. Pharaoh ants have been found entering wounds, and it is
known that they are able to carry over twelve pathogenic
bacteria. Researchers in Chile have found that it is possible for
the Argentine ant to harbor human enteropathogens such as
Shigella flexneri. Staphylococcus aureus, enteropathogenic
Escherichia coli. and Bacillus cereus. Management should be
directed at removing ants from certain areas of the home, but not
at removing them from their natural surroundings.
B. Pharaoh ant and Argentine ant biology
1. Pharaoh ants
The pharaoh ant is a tropical ant that nests where the
temperatures are between eighty and eighty-six degrees
Fahrenheit. In the continental United States it is most often
found in heated buildings, but is occasionally found outdoors if
the weather is suitable. Mating occurs in the summer, and more
than one queen (each laying hundreds of eggs) may occupy a nest.
When kept in the laboratory at twenty-seven degrees Celsius and
80 percent relative humidity, it takes thirty-eight days for
workers to emerge from the eggs. Although this species can feed
on sweets, it prefers fatty foods, and preys upon bedbugs, white
grubs, and other insects.
2. Argentine ant
The Argentine ant is a native of South America but is now
established in Arizona, California, Oregon, Washington, Hawaii,
Illinois, Maryland, and in southern states. It is a plant pest as
well as a house-invader, and has been widely transported by human
activity. One aspect of its behavior which seems to have aided
its travel is its ability to survive in water. Individuals are
known to alternately swim and walk on the surface of water upon
which dust has collected. As a group, they can cluster in balls,
with immature stages being kept in the center and workers and
queens on the outside. Workers continually scramble to the top as
more individuals are added and in so doing allow air to reach the
immature ants locked in the ball's center. Along with their
"swimming" ability, Argentine ants have proliferated because they
lack natural enemies, can form extended colonies, and have hardy
and numerous queens. While Argentine ants fall prey to the yellow
hammer (Colaptes auratus), the English sparrow, and nymphs of the
cockroach Thyrsocera cincta, they are basically free of natural
enemies in the lands that they invade. Temperature and moisture
are the most natural avenues of control.
Argentine ant nests are shallow and often located under
boards or rocks, among tree roots, and under the sidewalk. In the
summer, the ant nests are small and scattered, but as the weather
cools, the colonies coalesce into one larger nest placed deeper
into the soil or nearer to artificial warmth. Absence of these
ants from drier climates indicates a strong need for moisture.
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They are notably drawn to warm moist areas like those offered by
decaying plant material. In the early 1900's Newell made use of
these facts and found that during cool weather, ants could be
lured to a box of compost which could then be fumigated. (Dry ice
would be the fumigant of choice today.) During the warm months,
Newell found that the ants could be lured to decaying wood placed
in a cool spot and baited with a nearby food source (a jar of
honey or sugar). After the nesting place was occupied, the
infested wood was submerged in boiling water and later reused.
Common sense techniques such as these deserve attention and might
easily be incorporated into least-toxic control programs.
Unlike other ants, Argentine ants are very friendly with
same-species ants from a different colony. This behavior
facilitates establishment of extensive community systems that
revolve around a common food source, but it also makes their
elimination more difficult. In addition, each nest can have more
than one queen. These queens are active in feeding and grooming
the young, and have been seen travelling along worker trails.
Since Argentine ant queens mate when in the nest, they avoid the
exposure period experienced by termite reproductives and increase
their chance of survival.
To non-species members, Argentine ants are quite
aggressive. In fact, they have displaced native ants in certain
areas. While doing somewhat of a service by displacing the
stinging agricultural pest S. xyloni in parts of California, the
Argentine ant has also caused a significant problem in California
citrus orchards by protecting honeydew-producing insects from
their natural enemies. (Honey dew is a sugar/protein mixture
derived from sap plants and exuded naturally by plant-sucking
insects).
The extensive range of the Argentine ant can also be
attributed to its omnivorous habits. Small insects such as flea
larvae, young cockroaches, bed bugs, and other pests are "indoor"
foods, whereas thrips and lacewing and ladybird beetle larvae are
"outdoor" foods. Food is shared by regurgitation and it has been
found that food consumed by one worker can be passed to 156 other
colony members in forty-eight hours. Sugars are used most by the
workers, whereas proteins are reserved for larvae and the queen.
In the past, sugar has been the bait used to carry toxicants such
as boric acid. But, it is possible that a greater proportion of
the poison could be transported directly to the young if an
appropriate mixture of sugar and protein could be derived.
C. Ant detection
Before treatment (preventative or direct) can begin, it is
necessary to determine whether or not the invading ant is a
carpenter ant. If it is not, the first step is to locate the
attracting food source. It is then necessary to find the entrance
point and the nest site, and to determine whether the ant is a
biter or a stinger.
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D. Ant prevention
1. Introduction
Since ants need food, water, and refuge like any other
animal, denying them access to any or all of these resources can
greatly decrease their number. Measures taken to eliminate ant
presence will also help to reduce invasion by other insects such
as cockroaches, flour beetles, and moths which are accompanied by
their own predators (i.e. spiders, centipedes etc.). Each
permanent change will simplify subsequent preventative measures.
2. Elimination of food sources
a. Food storage containers
Reduction in available food sources involves use of
appropriate food storage containers, proper management of waste
materials, the use of permanent sticky barriers, and modification
of habitat. Ants are able to travel up the threads of a screw top
jar and enter it if there is no liner or rubber gasket.
Therefore, well-sealed jars and plastic containers with snap on
lids should be kept handy for food storage. Ants can enter
refrigerators but they cannot enter freezers due to their extreme
temperature.
b. Management of wastes
By nature, ants are decomposers of organic materials and
often seek out wastes on kitchen counters and in garbage pails.
To reduce the risk of infestations started in this way, kitchen
surfaces should be kept clean, and floors washed or vacuumed
frequently- It is further advised that food wrappings and food
containers be rinsed before being discarded. Leftovers of any
sort are ant-enticing and should be disposed of in sealed
receptacles, separate from other types of wastes, and set aside
for composting if desired.
3. Permanent sticky barriers
Food goods (e.g. pet food) that must remain in the open can
be protected by barriers. Ants will not cross sticky barriers
such as Stickera", TanglefootR, or Sticky Stuff". Dust decreases
the effectiveness of these barriers, but a downward-projecting
tuna can lid placed above them is a good way to extend their
effectiveness.
4. Modification of habitat
Once entry points have been located, silicone caulk can be
used to block them off. Silicone seals resists shrinkage from the
structure and can be "painted on" (especially helpful in larger
areas). Closing off cracks should be accompanied by the use of
.5-1
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sorptive dusts or desiccants such as silica aerogel, diatomaceous
earth, and boric acid dust.
E. Ant control
1. Chemical control of ants
a. Dusts
Creating a chemical barrier around the house foundation is
the traditional approach of pest control professionals. However,
it should be kept in mind that some species of house-invading
ants (e.g. Argentine ant) patrol the foundations of buildings and
act as a deterrent to subterranean termites. The use of non-toxic
barriers to prevent intrusion upon living spaces is therefore
preferred over foundation barriers. But if the use of caulk and
sticky barriers is ineffective, poisons can be used.
Sorptive dusts such as diatomaceous earth and silica
aerogel are particularly useful when blown into cracks and wall
voids before they are sealed. Boric acid dust can also be used.
If kept dry, these materials should be effective for years, and
should not harm the residents. No dusts, even "non-toxic" ones
should be inhaled.
b. Silica gel-pyrethrum combination
Although the treatments just mentioned are effective, they
are also slow to act. For quick knock-down, silica gels can be
combined with pyrethrum insecticides. These formulations should
be purchased in a container having an applicator which can set
the chemicals only where they are needed. Both Revenge™ and
Pursue™ have these applicators; Drione™ is a non-aerosol
formulation with an applicator like a plastic ketchup dispenser.
When dry, these products turn white and are easy to detect. They
also present a low level of hazard to mammals, can be easily
applied, and work guickly. Unfortunately, they are not cure-alls,
and ants are adept at finding new entry routes unless permanent
preventative measures are taken.
c. Insecticidai soap
Insecticidal soap or a soap-pyrethrum drench can be used to
kill ants directly or to force nest relocation when ants are L
outdoors but too near a structure. Once nests have been located,
the soap (e.g. Safer™ Insecticidal Soap) can be used to saturate
the site. (This may have to be done more than once.) If plain
insecticidal soap treatments are inadequate, pyrethrum
insecticides can also be used to drench the nest. Natural
pyrethrum or pyrethrins, derived from an African flower, are
less-toxic than laboratory formulations. Eco Safe Laboratories, a
supplier of powdered pyrethrum flower heads, suggests soaking 1.5
ounces of pyrethrum powder and 1 teaspoon of coconut oil soap in
a gallon of water overnight. Trails and nest areas can be baited
with the following recipe: 3 cups of water, 1 cup of sugar, 4
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teaspoons of boric acid or borax; hi-protein cat food or a
cockroach control bait can be substituted for this mixture. One
cup of the bait can be placed into three to six screwtop jars
that are packed half-way with cotton, and then saturated with the
bait solution. Lids are replaced, and a few small holes are put
in each as entranceways.
d. Boric acid baits
Baiting has two major advantages: it uses only a small
amount of poison and applies it directly to the target. However,
it works only if the target insect can locate the bait, feed upon
it, and through grooming and feeding behavior transfer the
toxicant to other colony members. Slow-killing toxicants ensure
that even developing young are exposed. Larger queens may take
longer to kill, and may in fact survive (along with unexposed
pupae) after all workers have died off and re-establish a colony.
In some ant species, workers can lay eggs which develop into more
workers or reproductives. The extensive intercommunication
between Argentine ant colonies make their eradication nearly
impossible. Given these facts, retreatment does not sound like an
unreasonable expectation. Commercially-formulated baits such as
DraxR, by R-Value of Georgia, have become available for use
against the pavement ant, thief ant, pharaoh ant, and little
black ant. DraxR is a mint-jelly based boric acid bait which
kills both queens and workers. It is formulated as a dust
primarily for cockroach control but is also labeled for ants.
Most baits are combinations of boric acid and a sugary
attractant.
e. Insect growth regulators
Insect growth regulators are available for the control of
the pharaoh ant and the fire ant. PharoridR, by Zoecon
Corporation of Texas, has the insect growth regulator methoprene
as its active ingredient. When mixed with an attractive bait, it
kills developing young by interfering with the molting process
and also sterilizes the queen. Methoprene's negligible acute
vertebrate toxicity makes it suitable for residential use.
Pharorid" and Drax can be combined into a two phase system, used
in conjunction with habitat modification and education of the
building's occupants.
Before this combination treatment is initiated, the use of
all other insecticides is suspended. Conventional insecticides
tend to scatter pharaoh ants, which promotes establishment of
satellite colonies and exacerbates the problem. Methoprene is
used in the first phase of treatment and relies on the presence
of workers for its transferal. If worker number is decreased in
this initial phase, less methoprene will reach the queen and
brood.
Occupants of the building should be informed that
elimination takes two or more months, and that during this time
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workers (in decreasing number) will still be seen. Worker
presence does not indicate program failure; it indicates that the
workers are actively transporting the toxicant. The residence
should be inspected and feeding and nesting locations mapped.
During this part of the treatment, occupant cooperation is
essential. All food sources other than the IGR bait must be
eliminated in order to maximize the ants' dependence on the
presented food. Nest sites such as stored paper supplies, boxes
of miscellany, and accumulations of inorganic trash must also be
eliminated or isolated on free-standing tables protected by
sticky barriers or soapy moats.
It may take six weeks before the PharoridR baits result in
a decrease in the number of ants. During the eight week treatment
period, seven visits to the bait stations for monitoring may be
necessary. Since colonies vary in the foods that they prefer,
bait foods should be tested prior to mixing with methoprene.
PharoridR comes in a small vial with 10 ml 10 percent AI (active
ingredient), and can be stored unopened for two years in the
refrigerator. The recommended bait includes two parts liver
powder, one part honey, and enough sponge cake to make a seven
ounce slurry. A half honey/half peanut butter mixture is also
suitable. The bait can be dispensed using a pencil eraser dipped
into the solution or as a segment of a "loaded" plastic straw.
Each dab or segment can work over a twenty-five square foot area.
Baits should be placed next to but not on the ant trails since
the latter seems have a repellent effect.
During the first week of monitoring, the baits should be
checked three to five days post-placement. Throughout the initial
phase of treatment, consumed baits should be replaced. The goal
is to get the ants to consume as much of the bait as possible, so
if necessary, more baits should be placed in areas where there is
the greatest amount of feeding. The stations should be checked
weekly for the next two weeks and for the remaining five weeks
checked every two. By week eight, the queens should be sterilized
although mature starving workers will be wandering around,
homeless and unable to feed themselves. These workers should be
cleaned up so that the program's effectiveness is apparent. In
the second phase of -the treatment, the methoprene baits are all
replaced by boric acid baits and all areas of entrance and
accessway are caulked.
A recent study by Banks, Williams, and Lofgren (1988)
investigated the use of insect growth regulators to control red
and black imported fire ants, S. invicta Buren and S. richteri
Forel. Fenoxycarb is one of a group of chemicals with a carbamate
moiety that acts as an IGR against a number of insects. It can be
used against cockroaches, mosquitoes, scale insects, psyllids,
termites, stored product insects, and some lepitopterous pests.
It has been shown to cause alterations in egg-laying and brood
development, and eventual death of most treated colonies. The
study reviewed here assessed the effectiveness of fenoxycarb in
controlling the red imported fire ant (RIFA).
In the laboratory, technical grade fenoxycarb was dissolved
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at 1.0 and 2.0 percent by weight in refined soybean oil. Oil red
dye was added to the solutions as a visible tracer. The oil
solutions were administered in 50 or 100 microliter pipettes to
laboratory-raised RIFA colonies. Each concentration of the IGR
and the control (uncontaminated oil) was tested against at least
three colonies. The colonies were given their normal diets
twenty-four hours after treatment and held in the laboratory
under controlled atmospheric conditions. Each colony was examined
twice a week for sixteen weeks, then monthly for a year (by which
time most colonies had either died or fully recovered). At every
observation, each colony was rated according to the estimated
number of workers and the quantity of brood (eggs, larvae, and
pupae). Effectiveness of the treatments was determined by
comparisons of colony indices (equal to, the value assigned to
the number of workers multiplied by the value assigned to the
brood quantity).
The oil solutions were readily accepted by the RIFA
colonies, although the 2.0 percent solution was removed more
slowly than the 1.0 percent solution, indicating possible
repellency of concentrated solutions. Dyed integuments proved
that a substantial amount of oil had been passed to the larvae
within twenty-four hours. All colonies exhibited effects of
fenoxycarb relatively quickly, with the most obvious sign being a
shift from worker brood to sexual brood production. Decline in
worker brood continued until no workers were present in any
colony (four to eight weeks post-treatment). At a 5 mg (AI) per
colony dosage, seven of the eight test colonies had died by
thirty-six weeks; the eighth colony completely recovered by week
thirty-two- Three of five colonies treated with 10 mg (AI)
fenoxycarb had died in a year; some recovery had occurred in the
other two colonies.
Fenoxycarb's exact mode of action is unknown, but the
disappearance of worker brood can be due to three possible
factors: mortality of the existing brood due to direct toxicity
(there is little evidence to support this) or through disturbance
of developmental processes, reduction or cessation of egg
production, or shift in caste differentiation from workers to
sexual forms. Mortality of colonies usually required six or more
months and was basically attributed to lack of worker replacement
and natural colony mortality due to age.
Four field tests were conducted in Georgia and Mississippi
to further evaluate the efficacy of fenoxycarb on natural
infestations of RIFA. Six bait formulations were applied to the
test plots with a tractor-mounted granular applicator. Similar
plots represented untreated controls. The efficacy of each
treatment was evaluated by carefully searching the plots before
and after treatment, then opening every nest with a shovel to
examine its contents. One method used assigned a number to each
colony, based on the estimated number of workers and whether or
not the colony had a worker brood. Another method employed in the
study assigned a rating for size to each nest. The total number
of ants per unit area was the number of mounds per category times
o
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the assigned average number of ants per mound.
Baits containing fenoxycarb were found to be very effective
at reducing the population indices of the RIFA colonies and also
the total ant populations in almost all treated plots. Worker
number dropped and worker brood was totally eliminated. All the
field tests showed that fenoxycarb was effective against natural
RIFA populations. An average of 60 percent of the treated
colonies were dead thirteen weeks after treatment, and about 33
percent more that had lived until the thirteenth week were
reduced to less than one thousand workers. Only about 13 percent
of the surviving colonies in treated plots contained any worker
brood, whereas about 94 percent of the untreated control colonies
contained worker brood. Field testing showed that application of
the bait to wet soil and vegetation can reduce efficacy.
2. Biological control of ants
a. Pyemote mite
Although ants have a number of natural enemies, only the
pyemote mite or itch mite is marketed for this purpose. It has
been used successfully to control fire ants outdoors and may also
be useful for killing carpenter ants living in trees. But, it can
present a problem for humans and is generally not suitable for
use near them.
b. Nematodes
Several species of insect-eating nematodes are commercially
available, although there is no data on their use against ants.
It is possible that a strain, harmless to humans, could be
developed for this purpose.
c. Coordinating colony cycle with treatment
Work reported by Markin in 1970 shows that many ant eggs
are produced between late February and early March, and that most
sexual forms develop from these eggs. Maturation of these
individuals occurs by May and mating occurs inside the nest when
females emerge from their pupae. The number of queens remains
constant until January or February of the following year when 75
percent are killed off by the workers. Workers are produced in
March, reach a number high in October, and decrease thereafter
until their number bottoms out in March or April. It has been
recommended that control measures be initiated in the fall and
that baits be kept available all winter when colony size is
dropping and the availability of nectar is low. Full scale
control efforts should start before warm weather provides food
and opportunity for the mother colony to fragment.
d. Disturbance of feeding trails
Studies done by Dechene (1970) illustrated that major
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15
foraging trails of the Argentine ant radiate outward from the
nest, and that they are reinforced by ant traffic. A worker will
follow the trail for a given distance, then wander up to a foot
away to forage. Directionality is apparently not implied in the
trail since workers that encounter it will follow it in either
direction. It has been found that removing the antennae of
workers deprives them of chemical and tactile stimulation, and
prevents them from locating trails. Even if a bit of trail is
removed, workers will become disoriented. Interference with ant
sensory reception is another potential mechanism of control.
3. Physical control of ants
Physically eliminating individual workers will do little to
suppress the infesting ant population, especially since new ants
are added so quickly. But, it is helpful to mop or vacuum up
workers that remain after controls have been implemented.
a. Detergent barriers
Detergent barriers are one way to stop ants from consuming
exposed edibles. Water alone is ineffective since ants use the
water's surface tension to make their way across non-soapy moats.
Adding detergent causes the ants to sink.
b. Flooding
Flooding can be used make ants move from flower pots or
away from a given area. A colony existing in a flower pot can be
encouraged to move by flooding the plant with water while
simultaneously providing an accessway or bridge to an adjacent
compost- or soil-filled container. The ants pick up their pupae,
head for the pot's rim, and travel across to safer ground. The
container can then be removed and disposed of. Hot or cold soapy
water is another simple control that can be used to wash nests
away from buildings. (Many ants nest outdoors and then wander
inside.)
c. Temperature extremes
Like all life forms, ants have an certain range of
temperatures outside of which they cannot survive. Most of the
techniques related to uses of extreme temperature are used
against carpenter ants and have been outlined in the previous
section. Ebeling has stated that Argentine ant workers forage day
and night, in light and dark. Also, that workers become sluggish
at forty-five degrees Fahrenheit and cease activity at
forty-three degrees Fahrenheit (activity is resumed if the ants
are warmed). The greatest amount of foraging occurs between fifty
and eighty-six degrees Fahrenheit. Findings such as these could
be incorporated into a control program to target insects when
they are vulnerable or to predict when they are most likely to be
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out and about.
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BIBLIOGRAPHY
Banks, W.A., D.F. Williams, and C.S. Lofgren. "Effectiveness of
Fenoxycarb for Control of Red Imported Fire Ants (Hymenoptera:
Formicidae)." Journal of Economic Entomology 81 (1) (February
1988): 83-87.
Collison, Clarence H. "Carpenter Ants." The Pest Sheet (The
Pennsylavania State University, Cooperative Extension Service)
(June 1978):1-3
Fowler, Harold G. "Urban Structural Pests: Carpenter Ants
(Hymenoptera: Formicidae) Displacing Subterranean Termites
(Isoptera: Rhinotermitidae) in Public Concern." FORUM:
Environmental Entomology 12 (4) (August 1983): 997-1002.
Heller, Paul R. "Ant Control in Home Lawns." The Pest Sheet (The
Pennsylvania State University, Cooperative Extension Service)
"How to Control Pharaoh Ants." The IPM Practitioner VIII (5) (May
1986.
Olkowski, Helga and William Olkowski. "Ants in the House."
Common Sense Pest Control Quarterly IV (4) (Fall 1988).
"The Argentine Ant: Pest and Predator." Common Sense
Pest Control Quarterly V (1) (Winter 1989).
Olkowski, William and Helga Olkowski. "Carpenter Ants." Common
Sense Pest Control Quarterly I (2) (Winter/Spring 1985).
,' r.
U-
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FLEAS
I. Identification of problem
II. Flea biology
III. Flea control
A. Introduction
B. Chemical control of fleas
1. Pets
2. Indoors
a) Introduction
b) Evaluation of chemicals on appropriate surfaces
c) Applications on nylon carpet
3. Outdoors
C. Less toxic controls
1. Fatty acids, pyrethrum, and limonene
2. Diatomaceous earth, pyrethrins, and methoprene
3. Pet care, "lures", and vitamins
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FLEAS
I. Identification of problem
Fleas are able to transmit a number of diseases to man. One
is plague. Although there have been no reported epidemics in the
United States since 1925, the plague is present in the wild
rodent population in the western states and a few cases occur in
humans each year. Murine typhus is another disease transmitted by
fleas, but it primarily affects rats and mice. Transmission of
the pathogen is believed to occur when flea feces enters the
wound when the host animal scratches. About forty cases of murine
typhus are reported each year in the United States. Both people
and pets can have allergic reactions to flea bites. However,
since humans are often not the preferred host, they are only
bitten when infestation levels are very high or when the pet host
is absent. Bites on humans occur from the mid-calf down and
appear as small red bumps, three to four in a line.
II. Flea biology
Fleas are small, wingless, dark-colored insects with narrow
bodies that enable them to move easily between body hairs. Their
last pair of legs is modified for jumping and their mouthparts
are adapted for piercing skin and sucking blood. Whisker-like
spines on their head are used for identification. There are three
well-known species of fleas: the cat flea (Ctenophalides felis),
the dog flea (C. canis), and the human flea (Pulex irritans). The
cat flea can attack dogs, cats, humans, and other animals.
The life cycle of a flea can be divided into four stages:
egg, larva, pupa, and adult. Eggs are often deposited on a pet,
in the pet's bedding, or in cracks and crevices of floors. In
about a week the eggs hatch into worm-like larvae which live not
on fresh blood but on organic matter such as dried blood and
adult flea excrement. In twelve days the mature larvae change
into pupae. If food is plentiful, the pupal stage may last for
only seven days; if a host is unavailable, it can extend for over
a year. Adults feed more than once a day on fresh animal blood
and live for over a year. They can survive for one to two months
without a meal, and for eight months having had just one. Since
adult emergence is triggered by the presence of a host,
reintroduction of a pet can bring about mass emergence.
III. Flea control
A. Introduction
Many conventional chemical treatments are on the market for
flea control. They include toxic collars, soaps, dusts, "bombs",
and "foggers". Fleas are most often controlled by the use of
chemicals applied to an infested pet, indoor areas, or outdoor
areas. The brief discussion which follows focuses on the
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application of chemicals at the first two sites. Due to their
toxicity and the generally high level of exposure experienced by
pets and people using them, chemicals are not recommended as part
of a least-toxic program. Less toxic control techniques are
outlined under the last heading of this section.
B. Chemical control of fleas
1. Pets
Pet treatment involves use of one of the. following
insecticides: carbaryl 5 percent dust, malathion 4 percent dust,
methoxychlor 4 or 5 percent dust, or pyrethrins 1 percent dust.
(Carbaryl cannot be used on kittens less than four weeks of age.)
If combinations of the above are used, component concentrations
should be lowered. Preparations usually come as powders, sprays,
and shampoos.
2. Indoors
a) Introduction
To eliminate infestations in the house, it is helpful to
first vacuum the rugs, floor, and the corners of each room and to
dispose of the bag. Application of bendiocarb, chlorpyrifos,
malathion, methoxychlor, or a household formulation of pyrethrins
kills larvae and adult fleas. Because dusts leave a deposit,
sprays are generally preferred. Floors, low wall areas,
furniture, and rugs should be treated, but with care since some
products can stain.
b) Evaluation of chemicals on appropriate surfaces
The seasonal pest C. felis (Bouche) is a serious veterinary
and public health problem. Indoor control has concentrated on
larval refugia and laboratory tests have basically involved
exposure of C. felis or Xenopsylla cheopsis (Rothschild) to glass
surfaces, filter paper, or soil treated with insecticide. Results
of these tests have not accurately reflected the efficacy of
insecticides when they are applied indoors. A more realistic
approach was taken by Rust and Reierson (1988) who applied
insecticides to common household surfaces. The following
insecticides were evaluated in their experiment: carbamates
(bendiocarb, bendiocarb plus synergized pyrethrins, carbaryl, and
propoxur), organophosphates (chlorpyrifos, diazinon, malathion,
and propetamphos), and natural pyrethrins and pyrethroids
(cypermethrin, fenvalerate, permethrin, pyrethrins, and
resmethrin).
C. felis larvae were collected from trays set beneath caged
cats and allowed to developed in a mixture of sand and dried
blood. Several hundred pupae eclosed in a jar with a screened lid
which permitted separation of one- to four-day old adults from
pupal cocoons. Adults jumped through the screen as the jar was
tipped and were then directed onto treatment surfaces via an
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inverted funnel. Three situations were evaluated. The first
involved seven to ten serial dilutions of each insecticide
applied to cotton fabric. The fabric was fastened to the inside
of a Petri dish and a 1 ml dilution was evenly applied to each of
five disks. Fifteen to twenty adult fleas were confined to the
treated fabrics under an inverted funnel and the number of
survivors counted after twenty-four hours.
Day old residues on cloth provided 50 percent kill in
twenty-four hours in this order of toxicity: chlorpyrifos >
diazinon = propetamphos > dichlorvos = diazinon 2FM > bendiocarb
= bendiocarb + synergized pyrethrins - synergized pyrethrins>
carbaryl = dioxanthion = propoxur > fenvalerate - malathion =
permethrin = resmethrin. Put simply, the organpophosphate
insecticides chlorpyrifos, diazinon, and propetamphos are very
effective at killing adult fleas.
Insecticidal activity was also evaluated on both thin and
dense nylon carpet with canvas-jute backing. The maximum volume
applied was 50.9 ml/m (more spray wetted the carpet too much and
caused mildew). The minimum applied was 26 ml/m2. Residual
activity was determined from the mortality found at twenty-four
hours among groups of twenty-five fleas confined to each of three
pieces of treated carpet. Fleas were tapped from the treated
disks into a basin of cold water and the number of living and
dead were counted. Control mortality was between 0 and 15
percent.
Day old residues of organophosphate and carbamate
insecticides applied at greater than 51 mg (AI)/m2 killed all
adults within twenty-four hours. Rates found for more than 90
percent kill of adults for six weeks were: carbaryl 1222 mg
(AI)/m2, diazinon 509 mg (AI)/m2, propetamphos 255 mg (AI)/m2, and
chlorpyrifos mg (AI)/m2. At lower rates only the last two
retained activity. Because pre-emerged adults can remain in their
pupal cocoon from three to twenty weeks, insecticides must be
active for at least twenty-one days in order to affect emerging
adults. The length and density of the carpet may have prevented
penetration of insecticides into the nap.
The effects of vacuuming, wear, and shampooing on residual
control were also tested. A carpet sample was treated with
bendiocarb, encapsulated diazinon, or propetamphos. The sample
was either left undisturbed or vacuumed with ten sweeps of an
upright vacuum cleaner weekly. To simulate walking, a drum-type
roller was passed over other sample pieces three times daily. One
piece of carpet was treated with each of the three insecticides
and rolled and vacuumed daily. Testing also included cleaning a
treated carpet with a carpet shampoo machine.
The activity of bendiocarb, diazinon, and propetamphos was
not found to differ significantly on undisturbed deposits aged
for three weeks. Residual activity of bendiocarb and propetamphos
did not decrease significantly when treatments were vacuumed,
rolled, or vacuumed and rolled. Activity of microencapsulated
diazinon however, declined under the same conditions although it
still gave over 83 percent kill. (Crushing the encapsulated
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insecticide allowed the active ingredient to volatilize more
rapidly than if it were left intact.) Shampooing decreased the
residual performance of both bendiocarb and microencapsulated
diazinon in three weeks but it did not significantly affect
propetamphos applications.
Generally, the organophosphate insecticides (except
malathion) provided the greatest activity against cat fleas when
treated on carpet. Synergized pyrethrins and carbamate
insecticides require 1.5-8.8 micrograms (AI)/cm to give 50
percent kill within twenty-four hours. Carbaryl, a commonly
chosen insecticide for this insect, was found to be the least
active carbamate tested. Very high amounts of pyrethroids (>30
micrograms/cm2) were needed to provide adequate kill. Determined
activity can be summarized as follows: organophosphates >
carbamates = synergized pyrethrins > pyrethroids. It should be
emphasized that residual activity for three to six weeks may be
necessary to interrupt the life cycle of the flea indoors since
room conditions can extend the pupal stage.
c) Applications on nylon carpet
The cat flea C. felis (Bouche) has been found difficult to
control on carpets using residual sprays. The problem may relate
in part to insecticide resistance. In fact, a study by El-
Grazzar, Milio, Koehler, and Patterson (1986) found that
tolerance to as many as nine insecticides occurred in a single
strain of cat flea. " Koehler, Milio, and Patterson (1986)
conducted a study to determine the residual toxicity to cat fleas
of commercially prepared insecticides when applied to carpets.
Fleas were reared on cat hosts at the ARS-USDA Insects
Affecting Man and Animals Research Laboratory in Gainesville,
Fla. Commercial preparations of microencapsulated pyrethrins
(0.16 percent), bendiocarb (0.50 percent), bendiocarb and
pyrethrins (0.50 percent), propetamphos (0.50 percent),
microencapsulated diazinon (1.00 percent), and chlorpyrifos (0.25
percent and 0.50 percent) were diluted in 100 ml water to the
above concentrations, and applied to the carpet at label rates
with a track feed sprayer at 1.41 kg/cm2, 4 6 cm above the carpet.
Short pile carpet samples (12.96 strands per cm nylon double
thread, 1 cm height, jute backing) were treated individually with
an insecticide and allowed to dry for four hours. Each sample was
then cut into thirty-six square inch pieces which were allowed to
age and were subsequently evaluated in the laboratory at twenty-
six degrees Celsius and 50 percent relative humidity. Carpet
residues were evaluated at one, two, four, seven, fourteen, and
twenty-one days posttreatment. At each of these times, five
samples were picked at random for each compound and placed in a
250 ml glass hydrometer cylinder. Ten cat fleas were placed on
the carpet in each cylinder. After twenty-four hours, the carpet
was removed and examined for living and dead fleas.
All the insecticides except 0.5 percent bendiocarb and 0.16
percent microencapsulated pyrethrins caused mortality one day
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posttreatment. But by day two, the 0.5 percent bendiocarb and
0.25 percent chlorpyrifos also failed to cause significant
mortality. Fourteen days posttreatment 0.5 percent bendiocarb and
pyrethrins, and twenty-one days posttreatment 0.5 percent
propetamphos failed to provide significant mortality- High levels
of mortality were achieved but high levels of control were not.
At two days posttreatment, only 0.5 percent chlorpyrifos caused
more than 80 percent mortality. It caused greater than 90 percent
mortality for a week before its efficacy declined.
From this study it can be concluded that insecticides
applied to nylon carpet (one of the most commonly treated
surfaces) do not provide long-term protection against fleas.
Registered insecticides provided control only for one to seven
days. Three factors seem to be contributing to this finding. One
is that carpet has a greater surface area per square centimeter
than other treated surfaces, therefore less active ingredient per
unit area is present. Second, carpet density prevents complete
coverage of the treated area. Third, since the carpet is a
synthetic organic material, synthetic organic pesticides may be
moving into the fiber matrix and becoming unavailable to the
fleas. Poor residual control is the net result of these factors.
New formulations and application procedures appear to be
necessary. Insect growth regulators represent an effective
alternative to these conventional insecticides.
3. Outdoors
Outdoor methods of control should begin in the summer and
early fall. One of the following chemicals can be used:
bendiocarb, carbaryl, chlorpyrifos, diazinon, malathion
methoxychlor, or propoxur. All safety measures detailed on the
label should be followed.
C. Less toxic flea controls
1. Fatty acids, pyrethrum, and limonene
Safer, Inc. of La Mesa, California offers a variety of
products for insect control in the house, in the garden, and for
pets. Entire™ Flea and Tick Spray is a combination of fatty
acids and natural pyrethrum that can be applied to pets and to
infested areas.. Fatty acids are a basic energy source and a
building block of cell membranes. A select few can serve as
insecticides by penetrating the body of a susceptible insect and
acting as membrane disrupters. Essentially the fatty acids "punch
holes" in the cell membrane by binding to carbohydrate or protein
receptors. This alters normal membrane permeability and cellular
physiology and causes the cell contents to leak out, resulting in
the rapid death of the insect or mite. Unlike conventional
petrochemical-based insecticides, fatty acid formulations need
not be ingested by their target. They are also biodegradable, do
not accumulate in the food chain, and can be combined with other
chemical formulations to create a broad spectrum insecticide.
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Once the formulations are dry, they are no longer effective.
Safer™ Indoor Flea Guard and Safer M Flea Soap for Dogs and Cats
are combinations of potassium salts and fatty acids. (The salts
upset the ion balance of the membrane.) Two other products by
this company (Insecticidal Soap for Houseplants and Mite Killer)
are also based on these ingredients and are used against red
spider mites and two-spotted mites. It is also known that
limonene, a citrus fruit extract, is effective at repelling
fleas.
2. Diatomaceous earth, pyrethrins, and methoprene
Diatomaceous earth, mentioned previously for the control of
termites and ants, can also be sprinkled into furnishings
frequented by flea-ridden pets. Pyrethrins (esters of pyrethrum,
an extract from the chrysanthemum plant) and the insect growth
regulator methoprene are other alternatives. Pyrethrins are very
toxic to fleas but have low mammalian toxicity. Methoprene works
by interfering with flea development and also has relatively low
mammalian toxicity. Researchers at the Bio-Integral Center have
stated that methoprene is active for six months against
developing fleas.
3. Pet care, "lures", and vitamins
Restricting a pet to a single bed enables the owner to wash
bedding frequently to remove adult fleas and larvae. Bathing an
animal and grooming it with a metal comb (dunked into soapy water
after each stroke) can also decrease the number of fleas. If
homeowners are planning to be away for a few days, a goose-necked
lamp left lit on the floor above a bowl of soapy water can act as
an attractant, drowning enticed fleas. Taking vitamin. B1 as
Brewer's yeast has been found to reduce the frequency of flea
bites. (This form should be given to pets in small quantities to
avoid cramping.) B-complex vitamins serve the same purpose.
<1 L
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BIBLIOGRAPHY
Atkins, Michael, Senior Vice President of Product Development and
Registration of Safer, Inc. Interview by author, 30 October
1989.
El-Gazzar, L.M., J. Milio, P.G Koehler, and R.S. Patterson.
"Insecticide Resistance in the Cat Flea (Siphonaptera:
Pulicidae)." Journal of Economic Entomology 79 (1) (February
1986): 132-134.
Green, Stanley G. "Fleas." The Pest Sheet (The Pennsylvania State
University, Cooperative Extension Service) (September 1984).
Koehler, P.G., J. Milio, and R.S. Patterson. "Residual Efficacy of
Insecticides Applied to Carpet for Control of Cat Fleas
(Siphonaptera: Pulicidae)." Journal of Economic Entomology
79 (4) (August 1986): 1036-1038.
"Least Toxic Control of Fleas in Homes." An NCAMP Pest Control Fact
Sheet (National Coalition Against the Misuse of Pesticides).
Rust, Michael K. and Donald A. Reierson. "Performance of
Insecticides for Control of Cat Fleas (Siphonaptera:
Pulicidae) Indoors." Journal of Economic Entomology 81 (1)
(February 1988): 236-240.
"Safer™ The 1989 Catalog of Natural Plant Care Products." Safer,
Inc. Printed in the U.S.A. 1988.
"SaferR Insecticide Concentrate Technical Bulletin." Safer, Inc.
1989.
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TICKS
I. Identification of problem
II. Tick biology
III. Tick prevention
IV. Tick control
A. American dog tick
B. Brown dog tick
C. Repellents
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TICKS
I. Identification of problem
Ticks cause and transmit a number of diseases. Dermatitis
for example is caused by the tick's secretions or its bite. Tick
paralysis is another condition known to affect cattle, sheep,
dogs, and humans (especially children). It is believed that a
poison passes from a feeding female tick to the host. In humans,
the initial symptom is loss of feeling and muscular coordination
in the legs, followed by paralysis which continues up the body to
the arms, throat, heart, and lungs. Although death is possible,
recovery can be rapid if the tick is located and removed. Both
the wood tick and the brown dog tick can cause this ailment.
Rickettsia rickettsii, the disease organism responsible for
Rocky Mountain spotted fever, is transmitted by the American dog
tick. Most cases occur in the eastern United States and men,
rodents, and rabbits are all susceptible. Two weeks after being
bitten by an infected tick, a body rash will develop, accompanied
by high fever, headache, and muscle pain. Antibiotics and
vaccinations are available to treat this disease, but since ticks
wander about their host for as long as two hours before they
settle down to feed, the best way to prevent transmission is to
catch the tick while it is still moving. A pregnant female tick
can acquire the disease by biting an infected host and pass it on
to her offspring. This transferral can go on for six to eight
generations. The magnitude of the problem is easily seen when one
considers that a single female can lay over six thousand eggs.
Tularemia, a disease of rabbits and rodents, is highly
infectious to man and can occur through transferal of ticks,
through contact with the tick's body fluid or feces, or by
contact with an infected rabbit or rodent. The disease agent is
able to penetrate unbroken skin. Symptoms include swelling at
the bite site, swollen lymph glands, fever, muscle pain, and
weakness which can last for months. Anemia and death are possible
results of transmission. The American dog tick and the brown dog
tick are both carriers of this disease.
II. Tick biology
Ticks and mites belong to the class Arachnida. Unlike the
members of the class Insecta which we have been discussing, adult
ticks have eight legs and have neither antennae, compound eyes,
wings nor body segments. All are parasitic and live on the blood
of vertebrates. The three species of ticks to be considered here
are: the American dog tick (Dermacentor veriabilis), the brown
dog tick (Rhipicephalus sanguineus), and the lone star tick
(Amfalyomma americanum (L.)). The second species is an important
household pest but only a potential vector of disease since it
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generally does not attack man. A. americanum, found throughout
the southeastern United States, is a primary concern because its
presence on dogs can permit pathogen transfer to humans.
The American dog tick is inactive in the winter but it can
be found ready and waiting to attach to a passing host in the
spring and summer. Since it will not establish itself inside the
house, indoor control is unnecessary. In contrast, the brown dog
tick can live in the home year round and uses dogs almost
exclusively as hosts. Various features can be used to distinguish
between these two ticks. For example, the basis capituli (base of
the mouthparts) has rounded ends in the American dog tick but
pointed ends in the brown dog tick. The scutum or back plate of
the ticks is another distinguishing feature. Its color tells the
species and its size tells the sex. The scutum of the American
dog tick has silverish or whitish markings which stand out from
the color of its back whereas the back of the brown dog tick is
all one color. In males, the scutum covers the entire back but in
females only the front part of the back is covered.
The life cycle of the American dog tick takes about two
years to complete and goes as follows. In the spring, females lay
4,000 to 6,500 eggs. The eggs hatch into six-legged "larvae"
which actively search for food (rabbit or rodent blood), although
they can live up to a year without any- Once a larva finishes its
meal, it drops to the ground and molts into a nymph. The nymph
must then locate another rodent host. Once the adult form is
reached, the tick is able to select larger host such as dogs and
cattle. Once an adult female has engorged herself, she is able to
lay eggs. Adults can live for two years without food.
All stages in the life cycle of the brown dog tick rely on
a dog for a host. Between meals, the tick hides in crevices in
the house. Breeding in the house is unaffected by the change in
seasons so any stage is likely to be found on the dog or in the
house at any one time. The brown dog tick will occasionally use
man as a host.
III. Tick prevention
Preventative measures start with thorough examination of
animals or people that are returning from an outing. If a tick is
found feeding, it needs to be irritated enough so that it will
withdraw. Applying alcohol or gently pulling the tick off with
tweezers should do the trick but this procedure should be done
carefully so that its mouthparts are not left behind. The wound
should be cleaned with antiseptic and the remover's hands washed
to eliminate germs present in the tick's secretions.
IV. Tick control
1. American dog tick
Appropriate control measures again center around knowledge
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of the species type and its behavior. With regard to the American
dog tick, it is only necessary to remove the ticks from the dog.
But if the source of ticks is an area around the home, that area
can be sprayed with carbaryl, diazinon, chlorpyrifos, or
propoxur.
Koch and Burkwhat (1983) established and compared base-line
data on the effectiveness of a number of acaricides against an
Oklahoma strain of D. variabilis. Collection of such data is
useful in detecting the development of resistance and in
selecting acaricides for further study. Larvae fed on domestic
rabbits and were later placed in covered plastic containers and
allowed to molt under controlled atmospheric conditions. Because
studies involving A. americanum have shown that susceptibility is
dependent on age, the nymphs selected for the study were five to
seven weeks post molt.
First, the acaricides were dissolved in acetone. Then, 1-ml
glass pipettes were immersed in the proper acetone dilution and
allowed to dry for twenty minutes. (This period may have allowed
dichlorvos to vaporize which resulted in its reduced residual
effectiveness.) The larger opened ends were covered with cloth
and secured with a latex band and the smaller ends broken to
permit entry of the ticks. Ten nymphs were aspirated into each
treated or untreated tube with a vacuum pump and the narrow
broken off tips resealed with clay. All pipettes were held for
twenty-two to twenty-four hours at about twenty^seven degrees
Celsius and over 90 percent relative humidity- Mortality counts
were then immediately made. Ticks were considered dead if they
did not respond when prodded or blown upon. LC50 and LC90 values
(lethal concentrations) were determined from the tests using an
average of eight replicates for the six acaricide concentrations
used.
Results showed that the carbamates propoxur and bendiocarb
were the most effective acaricides. Lindane, amitraz,
chlorfenvinphos, and carbaryl were the next most effective, with
nearly identical LC5Qs. Ronnel, malathion, and rotenone were
found to be the least effective compounds. Results proved that
several acaricides are effective against D. variabilis.
Field evaluation of free-living populations has been
performed by Koch, Burkwhat, and Tuck (1985) using A. americanum
(L.). Their study described a method used to evaluate acaricidal
dips for dogs and reported results obtained from certain marketed
products. Male and female beagles one to three years old and of
medium weight were obtained from a professional handler. Woodlots
with concentrations of A. americanum were located in Cherokee
County, Oklahoma. Sample sites were flagged with surveyor's
ribbon and on the first testing day dry ice was placed on the
ground to stimulate host-seeking activity.
Thirty minutes later, three leashed dogs were brought to
each site. The groups of dogs were moved to different sites after
fifteen to thirty minutes and then removed from the area after an
hour total exposure. Four to five hours later, attached adults
and nymphs were counted by inspection before the dogs were housed
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in an outdoor kennel near the laboratory.
Tick-infested dogs were randomly assigned to treatment
groups (three per group). Each dip was prepared according to
label recommendations by mixing the calculated dose in about 15
liters of tap water. Each dog was completely submerged for
several seconds and then penned singly or with a dog of the same
treatment group to prevent cross-contamination. One group of dogs
in each trial was dipped in water and served as a control. Live
ticks (those that moved normally) were counted and removed
twenty-four hours after treatment; dead ticks were noted and also
removed. Infestation rates averaged one-hundred ticks per dog
during the two years of study. Treated groups were returned to
the lots at three, seven, twenty-one, twenty-eight, and thirty-
five days after treatment to determine the residual activity of
each acaricide. (Treatment groups showing no mortality were not
exposed to the ticks.) After exposure, counts were again taken at
four or five hours and again twenty-four hours after exposure
(the delay allowed time for ticks to attach). Most host grooming
was noted during the attachment period, although removal of
attached ticks was found to be minimal.
Results of the tests showed that all the acaricides tested
(except for pyrethrins) caused complete mortality of A.
americanum (L. ) attached to dogs on treatment day, but that
levels of activity dropped for all the acaricides thereafter.
Because ticks attached, it is assumed that the tested acaricides
lack repellent properties. This testing method employed natural
populations and infestations, but because there was a decline in
the average number of ticks per untreated dogs it also proved
that an unegual ectoparasite pressure existed. Population
fluctuations are often encountered in field trials and complicate
interpretations of results. A similar method of study was used by
these researchers to evaluate the effectiveness of acaricide-
impregnated dog collars against A. americanum. Similar studies
using the American dog tick or the brown dog tick are possible.
2. Brown dog tick
If the brown dog tick is the problem, both the home and the
dog must be treated. Dogs can be dusted with one of the
following: 5 percent carbaryl, 5-10 percent methoxychlor, 3-5
percent malathion, 1 percent rotenone, or a commercial tick or
flea powder. Cracks and crevices in the house and the dogs
bedding should be treated carefully, using either 5 percent
malathion dust or a 2 percent to 0.5 percent diazinon spray. Rugs
and furniture should be vacuumed. During the warm months it may
also be necessary to treat areas around the home.
3. Repellents
The following can be used as repellents when visiting areas
likely to be infested with ticks: diethyltoluamide, ethyl
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hexanediol, dimethyl phthalate, dimethyl carbate, Indalone and
benzyl benzoate. Protection lasts only a few hours.
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BIBLIOGRAPHY
Green, Stanley- "Ticks." (The Pennsylavania State University,
Cooperative Extension Service) (January 1980): 1-4.
Koch, Henry G. and Henry E. Burkwhat. "Susceptibility of the
American Dog Tick (Acari: Ixodidae) to Residues of Acaricides:
Laboratory Assays." Journal of Economic Entomology 76 (2)
(April 1983): 337-339.
Koch, Henry G. , Henry Burkwhat, and Marty D. Tuck. "Field Method
for Evaluating the Effectiveness of Acaricides Against Lone
Star Ticks (Acari: Ixodidae) on Domestic Dogs." Journal of
Economic Entomology 78 (1): 287-289.
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BEETLES
I. Cockroaches
A. Identification of problem
B. Cockroach biology
1. Appearance of adults
2. Likely habits
3. Cockroach life cycle
C. Cockroach detection
1. Means of entry
2. Monitoring existing populations
D. Cockroach prevention
1. Anticipation of cockroach mobility
2. Habitat modification
a) Eliminating water sources
b) Eliminating food source
c) What attracts cockroaches
d) Sealing potential harborages
E. Cockroach control
1. Aesthetic injury level
2. Chemical control of cockroaches
a) General use of chemicals
b) Some aspects of resistance
(1) Responses to propoxur (a carbamate
insecticide)
(2) Effects of synergists on bendiocarb and
pyrethrin resistance
(3) Pyrethroid resistance
c) Boric acid
d) Insect growth regulators
(1) Exposure effects of hydroprene and fenoxycarb
(2) Treatment and retreatment effects using
hydroprene
(3) Effects of fenoxycarb on technicians
e) Photodynamic dyes
f) Anacardic acid
3. Biological control of cockroaches
a) Use of hymenopterous oothecal parasitoid
b) Potential use of fungi •
4. Physical control of cockroaches
a) Household measures
b) Ultrasound
c) Zap Trap™
5. The Asian cockroach: new control problem
II. Wood-boring beetles
A. Identification of problem
B. Biology of wood-boring beetles
I. Introduction
2. Lyctid beetles
3. Anobiid beetles
4. Cerambycids (the old house borer)
C
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5. Non-reinfesters
C. Detection
D. Prevention
1. Inspection
2. Sealing wood surfaces
3. Reducing available moisture
4. Storing firewood outdoors until it is needed
5. Debarking stored logs
6. Using kiln- or air-dried lumber
7. Using boron compounds
E. Control
1. Chemical controls
a) Fumigation
b) Pyrethrum
2. Physical controls
a) Coating exterior surfaces
b) Temperature and humidity variation
c) Electrogun™
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BEETLES
I. Cockroaches
A. Identification of problem
One of the most well known but least popular insects is the
cockroach. There are over 3,500 species existing throughout the
world, fifty-seven of which are found in the United States. The
truly pestiferous species are German, brown-banded, Oriental,
smokeybrown, and American. Cockroach presence is considered
"socially unacceptable", and the insect's unpleasant odor and
ability to contaminate food with disease organisms make finding
alternative methods of control a worthwhile pursuit. The German
cockroach is the most widespread pestiferous species, its
cosmopolitan distribution due largely to man's dispersive
tendency- It is known to cause allergic reactions in 61 percent
of asthmatics and 27 percent of nonatopic children. Cockroaches
have been linked with transmission of the pathogens that cause
food poisoning, toxoplasmosis, infectious hepatitis, polio, and
amoebic dysentery -
Koehler, Patterson, and Brenner (1987) found that, out of
1,022 apartments surveyed in north-central Florida, 97.5 percent
were infested with German cockroaches. Data indicated that half
of the apartments had over 13,000 cockroaches, with the average
apartment having 19,647 cockroaches. Although monthly control
measures were followed in some cases, apartment dwellers still
faced unacceptably high infestation levels and constantly risked
exposure to pathogenic agents carried by the cockroaches.
Resistance of the insect to currently used pesticides is probably
a contributing factor. The need to re-evaluate conventional
treatment techniques is clearly pertinent, as is the need to more
extensively explore alternative measures of control.
B. Cockroach biology
1. Appearance of adults
The adult German cockroach (Blattella germanica) is about a
half-inch long with two dark stripes on its thorax; young are
one-sixth to one-half an inch long. The brown-banded cockroach
(Supella longipalpa (F.)) is similar to the German cockroach in
size, but has two light-colored stripes across its body. Adult
Oriental cockroaches (Blatta orientalis) are black and about an
inch long. Adult American cockroaches (Periplaneta americana
(L.)) are 1.5 inches long.
2. Likely habitats
Cockroaches are found in caves, animal nests and burrows,
and human habitats. They commonly dwell in restaurants, eating
areas, and bathrooms where food and water supplies are plentiful-
Warm, moist microclimates such as these are similar to those
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found in their native tropical habitat, East Africa.
German cockroaches prefer kitchens and baths but are
occasionally seen outdoors and can exist in heated buildings as
far north as Alaska. Although less abundant than the German
cockroach, the brown-banded cockroach presents a more difficult
control problem since it can tolerate drier conditions and will
roam throughout establishments. This species is a major urban
pest across the United States but is especially troublesome in
the South.
Adult Oriental cockroaches emerge from heat tunnels,
sewers, and similar places in the spring and may then invade
buildings. They can live year round in basements and are often
seen in the summer and fall in lit outdoor areas. American
cockroaches also inhabit the lower floors of buildings and can
live in dumps, wood piles, and sewers if the weather is warm.
They are the most avid fliers of the group. The smokeybrown
cockroach is common in southern states and lives in wood and
debris piles unless cool temperatures or lack of food drive it
indoors.
3. Cockroach life cycle and daily behavior
Female German cockroaches carry their egg capsules
(oothecae) for most of the incubation period (other house-
invading cockroaches simply deposit them in a safe place). The
incubation period is temperature dependent but at eighty-five
degrees Fahrenheit it lasts twenty-three days. Thirty-five to
forty-three nymphs emerge from each ootheca, and individuals go
through six or seven instars before molting into adults. The
average development period (nymph to adult) is also temperature
dependent but lasts seventy-four days at eighty-five degrees
Fahrenheit. Female German cockroaches can live for over six
months and produce about four oothecae (most other cockroaches
produce offspring only once). German cockroaches are thus the
most prolific of these species.
During the day cockroaches hide or rest in dark narrow
spaces such as cracks and crevices in or near human dwellings,
but at night they forage. German cockroaches become active as
soon as twenty minutes past dark; their activity increases until
it peaks near daybreak. The easy access to harborage and other
resources offered by most buildings make cockroach cohabitation
with people ideal (for the cockroach that is).
C. Cockroach detection
1. Means of entry
Cockroaches can enter a living unit from outdoor buildings
or dumps, or from an adjacent apartment. Pathways include heat
tunnels, plumbing, structural gaps between buildings, and
elevator shafts. Cockroach eggs can be introduced into buildings
by grocery cartons and sacks of vegetables.
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2. Monitoring existing populations
Cockroach presence is indicated by living or dead
cockroaches, cockroaches in traps, caste skins of different
stages, empty egg cases, or fecal droppings. Once cockroach
presence is established, a monitoring program can be initiated.
Using a flashlight, and pen and paper, a floor plan of the
infested area can be drawn up for note-taking. Monitoring is
particularly important when combating roach problems not only
because it locates infestations precisely in time and space, but
because it establishes a baseline population size from which to
determine the most cost-effective treatment program. For example,
data collected through monitoring can pinpoint where population
density is highest and consequently where to concentrate control
efforts. Monitoring, as stated before, also aids in evaluating
the effectiveness of instituted control methods.
Cockroach presence is usually assessed by flushing out the
insects with a pyrethrin aerosol spray. The use of traps however
is a more effective indicator than either flushing out or trying
to visually count the cockroaches. Most of the commercially
available traps are modeled on a prototype developed by Zoecon
Corporation of California. They usually consist of a small
rectangular cardboard box which has three bands of sticky glue
inside. Some offer baits such as burnt molasses. When and how
often to place traps is determined by the size of the given
population, the type of infested location, amounts of competing
attractants, and the resources and skill level associated with
the particular monitoring program. Aside from their use in
monitoring, baited traps can be used to a certain degree as
control tools, say for catching immmigrants in a "clean" area or
when insecticide use is impossible. Populations of cockroach
natural enemies can also be monitored, but this type of
monitoring requires special knowledge and must be done in
accordance with the sort of enemy (microbe, parasitoid, predator)
being trapped.
Another way to sample populations is with a jar trap (often
used in scientific experiments). The trap is usually a 128 ml
baby food jar coated with grease on the inner surface to deter
escapees. Two to three grams of white bread or beer may be used
as bait. Although this method is biased towards nymph-catch, it
is reasonably well standardized as opposed to the visual counting
and flushing techniques (however, these also include a good deal
of monitor bias).
Once a monitoring program has been established, control
measures can begin. Action is required when the pest population
threatens to reach or exceed the injury level. (A discussion of
the aesthetic injury level preceeds the topic of control.) No
absolute cockroach population level is used to indicate an
unacceptable degree of injury. Instead, this level is defined for
each treatment site. Contracts with pest control operators should
outline precisely how the situation's action point will be
determined, given the information obtained by monitoring the
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population.
D. Cockroach prevention
I. Anticipation of cockroach mobility
One major consideration in developing an effective method
of control is that cockroaches are always on the move. The battle
to prevent their recurrence can be constant and some believe that
the best preventative measure is chemical treatment of an area
every two to four weeks so that newcomers are killed and re-
establishment avoided. It has been found that urban
interapartment travel can be as high as 30 percent per week.
Runstrom and Bennett (1984) examined this movement through
a mark-recapture study of German cockroach populations in urban
apartments. A total of four buildings, each having four
apartments, were used. The floor plans for each were the same
except that adjacent units were mirror images of eachother. That
is, certain sets of kitchens and bathrooms were back-to-back and
serviced by a common plumbing system that divided the wall voids
between the units. About forty jar traps were placed in each
apartment overnight. All captured adults were marked on their
pronotum with a colored numbered tag (a different color was
chosen to represent each apartment for the given week of study)
Once tagged, the marked individuals were released into the site
of capture. Traps were set up in each apartment three more times
at weekly intervals. A total of six thousand adults were tagged
and sexed, and each was uniquely identified.
Insecticide was applied in individual apartments after the
third week of trapping to determine the effect on movement. The
apartment with the highest trap catch (greatest potential for
dispersion) was treated with chlorpyrifos (0.25 percent) plus
dichlorvos (0.25 percent). The other three apartments in the
building were monitored for twenty-four hours to check for
dispersion from the treated room. Recapture rates averaged 14
percent for all apartments. Of all the recaptures in a given
apartment which were "immigrants", 75 percent came from an
adjacent apartment having a common plumbing connection. In
thirteen of sixteen apartments, recaptures coming from adjacent
apartments were greater if the apartments were joined by plumbing
connections than if they were not.
Analysis of movement after pesticide application revealed
no significant effect on movement rates. Even though the
pesticide used contained dichlorvos (a flushing agent), movement
out of the treated area twenty-four hours after treatment was not
significantly different from that exhibited before treatment.
However, movement into treated areas was decreased in all cases
after pesticide application. Apparently a good deal of cockroach
control relates to modification of existing structures to inhibit
movement between living units.
2. Habitat modification
a) Eliminating water sources
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Habitat modification entails permanent preventative
alteration of the environment through elimination of attracting
resources. It has been found that female German cockroaches can
survive eighty days with food and water, but only thirteen
without them. It has also been found that females live longer
(forty-two days) on water alone than food alone (twelve days)
when kept at twenty-seven degrees Celsius. Further, that survival
increases with higher relative humidity. Obviously, reducing
water and humidity are key to lowering cockroach survival.
Sources of drinking water include condensation around
windows and pipes, leaky plumbing, and water-filled containers
such as those used for pets or for catching leaks from
appliances. The installation of barriers can sometimes help to
eliminate these attractants, but since reduction is often
insufficient building modification and food removal are most
often the chosen paths of prevention.
b) Eliminating food sources
Sanitation is another important aspect of prevention. Food
lodged in hard-to-reach places such as in cracks, beneath
baseboards, and behind cupboards encourages infestations, as do
opened packages of edibles. Glass or pressure-sealed plastic
containers should therefore be used to store food (cockroaches
can chew through paper and cardboard). Special efforts need to be
made in restaurants and food processing areas in recreational and
business establishments. In these areas garbage pickups should be
increased, especially if infestation levels are high or chronic.
Garbage containers, even if used with plastic liners, should be
cleaned regularly since all residues are attractive to
cockroaches. Effective population reduction in infested
establishments reguires careful examination and alteration of
maintenance procedures.
In a report which examined insecticide efficacy, cockroach
resistance, and the role of sanitation in control of the German
cockroach, Coby Schal (1988) stated that there was a positive
correlation between poor sanitation and higher cockroach
populations. Moreover, that poor sanitation lowered the efficacy
of otherwise effective insecticides. In some treatments, he found
that improved sanitation increased the efficacy of the
insecticide. Results such as these not only point to the role of
sanitation in cockroach control but they also emphasize the
interrelatedness of components in any least-toxic management
program.
c) What attracts cockroaches
Several types of compounds are thought to aid insects in
finding food. Many are products of the degradation of proteins
and fats, others are microbial components or products of
fermentation. Compounds which have been considered include fatty
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acids, esters, and alcohols. Products of animal decay (amines,
indoles, and sulfur compounds) are usually less attractive.
Roaches prefer diets high in carbohydrates with a minimum of fats
and protein. Breads are at the top of their list (as are the
dregs of a beer bottle), but response to animal proteins is very
low. Cockroaches probably choose among many volatile compounds
present in the air to locate desirable foods.
Isolation of attracting components can serve in directly
reducing cockroach number, in luring the pests to pathogens or
poisons, and in facilitating monitoring procedures. Although
carbohydrates and sugars stimulate feeding in insects, their
volatility is low and they probably could not act as long-
distance attractants in baits. Work with pheromones baits has not
been as effective as anticipated, results being complicated by
the fact that the studied pheromones must be perceived by touch.
d) Sealing potential harborages
Cockroaches are thigmotactic, that is, they prefer to have
their bodies touching the substrate. Spaces that accomodate this
need are easily found in poorly constructed or deteriorating
buildings. Adult German cockroaches can hide in cracks as small
as 1.6 mm wide and first instar larvae can squeeze through areas
1 mm wide. Such spaces should be caulked or otherwise sealed
according to the size and location of the gaps. In residences
with many cracks and crevices, sealing should begin when
monitoring indicates that populations are highest. Other
preventative steps include weatherstripping openings, replacing
or repairing windows and screens, and realigning doors. Air vents
like those found in kitchens can be screened to prevent cockroach
entry.
E. Cockroach control
1. Aesthetic injury level
The principles of integrated pest management (IPM) were
first tested and found effective within the context of
agriculture. But as IPM has expanded to include other ecosystems,
various factors have demanded consideration. For example, where
urban pest management programs are concerned, there is a need to
understand the close association between the target pests and
man, and to consider the sociological and physiological demands
of the public. Changes in relevant factors have led to an
alteration of the basic aim of IPM programs as they are applied
to certain situations. In agriculture, the aim remains to
establish an economic injury level (EIL)-- the lowest pest
population capable of causing economic damage— and to avoid
total eradication of the target population. While an EIL centers
on management techniques, urban IPM programs often involve strict
control measures dictated by prevailing attitudes and trends
regarding the pest. When Olkowski set up an urban IPM program for
street trees in Berkeley, California, he established an
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"aesthetic" injury level (AIL). The reasoning behind it was that
problem assessments are not always seen in economic terms;
aethetic considerations are sometimes also necessary before
treatments are pursued. I have introduced this concept here
because it relates most strongly to cockroach control.
Zungoli and Robinson (1984) conducted a survey in federally
subsidized public housing projects in Maryland and Virginia to
determine the attitudes of the residents towards the presence of
cockroaches in their homes. Results showed that 83 percent of the
residents surveyed perceived cockroaches to be a serious problem.
Association of the pest with food was found to be particularly
intolerable. Many residents expressed a feeling of hopelessness
concerning their ability to control the pest. Thirty-nine percent
of the residents did not believe that total elimination of the
cockroaches was possible and, of these, 72 percent believed the
problem was attributable to factors outside their control (e.g.
neighbors, lack of cooperation, cockroach movement). Those
experiencing the heaviest infestaions were willing to pay the
most for control.
It was also found that thirty-four percent of the residents
take action if they see one cockroach; 55 percent tolerate zero
to two cockroaches before they respond. For a control program to
satisfy 45 percent of the residents, it would have to ensure that
no greater than one cockroach would be seen in a twenty-four hour
period. Needless to say, such minimal tolerance of this pest
necessitates development of high caliber control techniques not
only to achieve a very high initial suppression goal but also to
maintain a consistently high level of effectiveness. In addition,
resident would have to be educated regarding the causes of
infestations and encouraged to cooperate with other tenants. An
underlying part of least-toxic control programs is a certain
degree of tolerance on the resident's part. But, as this study
shows, aesthetic tolerance can sometimes be so low as to make
establishment of an AIL impractical.
2. Chemical control of cockroaches
a) General Use of chemicals
Typically, liquid or aerosol ant and roach sprays, or baits
are the chosen methods of cockroach control. The sprays contain
quick killers or irritants (e.g. pyrethrins) plus a long-lasting
insecticide and are applied regularly to places from which
cockroaches emerge. They are also used to drive out Oriental and
American cockroaches hiding in openings around pipes and drains
in basements. Popular synthetic chemicals include
organophosphates, carbamates, and pyrethroids. Chlorpyrifos,
diazinon, propoxur, propetamphos, and pyrethrum (pyrethrins) have
all been associated with adverse health effects and cockroach
resistance to many has been found. Alternatives include boric
acid, amidinohydrazone, and hormone analogs. The acute toxicity
of the synthetic insecticides just listed is over five times that
of boric acid. Pyrethrum is 25 percent more toxic than boric
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acid. Boric acid comes in a non-volatile formula and may contain
less than 1 percent inert ingredients compared to the over 50
percent found in synthetic formulations. (Inert ingredient
content is a serious concern since inerts remain largely untested
for association with adverse health effects.) Aside from the risk
to the pest control operator, continual use of harmful
insecticides encourages the development of resistance in the
target pest and prolongs exposure of the environment to adverse
effects.
b) Some aspects of resistance
(1) Responses to propoxur (a carbamate
insecticide)
Widespread use of insecticides has affected insect
populations in two ways. One is the development of physiological
resistance, the other is behavioral change. Bret and Ross (1985)
found that a propoxur-resistant strain of B. germanica dispersed
less than a susceptible strain when exposed to propoxur vapors.
In fact, the resistant (BP) strain was found to be seven to eight
times more resistant than the susceptible (VPI) strain. The
selection for avoidance behavior due to insecticide pressure has
been positively correlated with physiological resistance in
certain species. A study by Ross and Bret (1986) detailed the
excitatory behavior elicited by propoxur in terms of movement and
grooming response.
Adult B. germanica males from both the BP and VPI strains
were used. In each replicate five males of the chosen strain were
confined on a piece of filter paper. Below them was placed an
aluminum pan containing the chosen solution and a wire screen to
prevent direct contact between the cockroach and the chemical. A
glass chimney, coated with petroleum jelly on the inside to
prevent escape and covered with a glass plate, was placed above
the cockroaches. Two out of the five cockroaches in each
replicate were marked with a dot of white correction fluid.
Movement in the set up was recorded with a video camera for five
minutes after exposure. When the video was played, movements were
traced using a piece of acetate placed over the television
screen. Eight repetitions were performed under the same
controlled conditions. The number and rate of antennal and tarsal
cleaning motions performed per minute for half an hour were also
visually recorded. Ten replicates, each the sum of five
individuals, were completed for each strain.
Experimental results indicate that exposure to propoxur
vapors causes an increase in movement and in antennal and tarsal
cleaning compared to that seen in controls. Control cockroaches
moved about the entire arena, going around the perimeter as well
as crossing its center. In contrast, exposed subjects
concentrated nearly all their movement at the perimeter. This
pattern was considered an avoidance response (an attempt to move
away from the source of irritation). BP males moved about more
than VPI males in both test and control situations, but the
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change of response between control and exposed conditions was
greater for the VPI males than the BP males.
Antennal grooming to remove the irritant from
chemoreceptors involved downward movement of the antenna and
flexion of the prothoracic leg over it to direct it towards the
mouth. Mandibles moved in a chewing motion along each antenna
from base to tip. (Tarsal grooming involved similar use of the
mouthparts, with most effort spent on the prothoracic legs.) No
rate changes between controls and test subjects existed. But,
upon exposure to the vapors, VPI males cleaned more frequently
and showed a 9.5-fold increase in the total number of antennal
cleanings over the controls; BP males showed only a 5.4-fold
increase. Loss of motor coordination due to intoxication
eventually resulted in a decrease in antennal grooming.
Exposure to the chemical caused a steady increase the
frequency of tarsal cleanings, with VPI males exhibiting a
greater increase than BP males. Results were partially influenced
by accumulation of petroleum on the antennae, lack of harborage,
and a relatively short period of acclimitization. Nonetheless,
the degree of change seen in each strain when compared to control
groups is significant, and points to a correlation between the
development of resistance and the expression of decreased
sensitivity to insecticide vapors.
(2) Effects of synergists on bendiocarb and
pyrethrin resistance
Resistance to bendiocarb is supposedly the most widespread
resistance problem in B. germanica. However, resistance that is
metabolic in nature can be negated through use of synergists such
as piperonyl butoxide. Cochran (1987) examined the effects of
synergists on reducing bendiocarb resistance and compared the
effects of different synergists on resistance to natural
pyrethrins in the German cockroach. Nymphal cockroaches of a
variety of strains were used in the experiment. Ten subjects were
placed in each of three jars which had been coated on their
interior with known amounts of chemicals. Time/mortality
responses were recorded until 90 percent of the cockroaches were
mortally affected. Data from the three replicates was pooled and
statistically analyzed. LT5Qs were calculated for each strain for
each chemical, and resistance ratios (RR's) were also found (LT50
resistant strain, R / LT50 susceptible strain, S). The chemicals
tested were: pyrethrins alone and with the synergists (piperonyl
butoxide or PBO, and MGK 264); bendiocarb (Ficam W) alone and
with the synergists; and pyrethrins plus bendiocarb with and
without synergists and bendiocarb (Ficam Plus). Bendiocarb was
applied at the rate of ten micrograms per square centimeter and
pyrethrins at the rate of three-tenths of a nanoliter per square
centimeter. Synergist concentrations were related to insecticide
concentrations in definite ratios (e.g. 1:1, 1:10, insecticide to
synergist).
As would be expected, neither synergist modified reponses
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10
of susceptible strains. But, MGK 264 rendered all but one
resistant strain almost totally susceptible. PBO was not as
effective at lowering resistance. Using two of the strains
(Mandarin and Kenly) and ratios of 1:2 and 1:3, it was found that
increased amounts of synergists decreased the resistance ratios.
These strains were also tested with natural pyrethrins, with and
without synergists. Kenly was found to be highly resistant
whereas Mandarin exhibited low resistance levels. A small
decrease in the RR for the Mandarin strain was recorded for use
of both synergists. Further testing of the strains with
bendiocarb plus pyrethrins and with or without synergists
uncovered an optimum ratio of 1:10 for pyrethrins and 1:3 for
bendiocarb. Both of the synergists reduced the resistance ratio
in both strains.
It can be concluded from this experiment that resistance to
pyrethrins and bendiocarb in the German cockroach can be negated
through the use of PBO or MGK 264 as synergists. Also that
commercial formulations of mixtures of these materials would
lower the resistance of a given strain. Ficam Plus (bendiocarb,
pyrethrins, and PBO) was used in this experiment and it did in
fact decrease the resistance of both bendiocarb and pyrethrins.
Supposedly, synergists act as inhibitors of microsomal mixed-
function oxidases.
(3) Pyrethroid resistance
Pyrethroid insecticides have been quite successful in the
control of insects because they can quickly immobilize
(knockdown) and kill the target pest. However, potential
resistance problems exist, especially in insects previously
selected by DDT and cross-resistant to pyrethroids. (It has been
indicated that the mechanism conferring cross-resistance relates
to a target site insensitivity (kdr).) Work by Cochran (1987)
illustrated the fact that certain strains of B. germanica can
develop resistance to a pyrethroid insecticide in as few as six
generations in the lab and probably two years in the field.
Synergists do lower resistance to pyrethrins, yet as resistance
extends to other pyrethroids it is expected that inhibition
effectiveness will drop. It has been strongly suggested that
control programs reserve the use of pyrethroids as alternatives
or for use with other insecticides, instead of using them as the
primary type of control.
c) Boric acid
Boron is a naturally-occurring element found in the earth's
crust and background levels of it are found in the human blood
stream. Boric acid, a derivative, is a safe and effective
alternative to conventional insecticides which does not create
the indoor air problems associated with insecticidal sprays. It
is significantly less repellent than chlorpyrifos, dichlorvos,
encapsulated diazinon, fenthion, malathion, propoxur, pyrethrins,
Cj Lj.
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and resmethrin. Its toxicity falls somewhere between that of
aspirin and table salt. But most importantly, in all the years
that it has been used, insects have not become resistant to its
very basic mode of action.
The best boric acid compounds have an anti-caking
ingredient to help keep the dust effective in damp areas and are
electrically charged to improve adherence to the insect. An added
safety feature of boric acid dusts is that they are blue or green
in color with a bitter taste to discourage children and pets from
ingesting it. Boric acid can be diluted and applied as a wash,
although it is more effective as a non-volatile dust which can be
applied around stoves, refrigerators, and ductwork, and in wall
voids or hard-to-seal cracks. Cockroaches walk through the dust
and pick it up on their legs, antennae, and body. The dust then
penetrates the cuticle and acts as a mild contact insecticide.
Grooming leads to ingestion, at which point the boric acid acts
as a stomach poison.
In a study conducted by William E. Currie, a member of the
IPM Unit at the U.S. Environmental Agency, it was found that
boric acid was a better treatment for cockroaches than
chlorpyrifos (DursbanR) . An aerosol formulation of boric acid was
applied in cracks in one area of a school cafeteria and
chlorpyrifos in another. Before application, Currie monitored the
sites using sticky roach traps to estimate population sizes. From
trapping data collected over a two year period, Currie found that
one application of boric acid reduced the average trap catches
from forty to three in three months. The single application of
boric acid maintained this average for three years. Two
applications and one retreatment with chlopyrifos were required
to achieve similar results. Of the two treatments examined, boric
acid was clearly the more cost-effective.
It has also been shown that boric acid plus 0.1 percent
Dri-die is more effective at controlling the occurrence of German
cockroaches during construction than boric acid alone, Dri-die
alone, and boric acid plus 0.1 percent Cab-O-Sil (an anti-caking
compound). Eighteen months after one application, only two
cockroaches emerged by flushing with a pyrethrin spray (used as
the monitoring tool). In contrast, untreated apartments averaged
thirty-one cockroaches.
Although the advantages of boric acid are well illustrated,
it is not as widely used as would be expected. Its major drawback
is its lack of "quick kill" (somewhat of a tradeoff for its long-
term effectiveness). Another disadvantage is that boric acid
dusts can be absorbed through skin lesions and also inhaled,
which necessitates following label precautions and wearing a dust
mask to prevent inhalation. Also, some pest control operators
find it too noticeable, difficult to properly apply, and not as
profitable a service to offer as conventional insecticide
treatment.
However, new advances in packaging and formulation are
counteracting negative opinions. Early boric acid containers had
poor applicators which caused the dust to form piles; piles cake
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and become ineffective since they are detected and avoided by
cockroaches. Products by R-value of Georgia include built-in
applicators for easy direction and application. R-Value has also
introduced an aerosol formulation that is particularly useful in
hard to reach areas. New packaging has lessened the need to
handle the material and also made it less likely that the
material will be stored in unmarked containers.
Boric acid, in the form of roach tablets, was the first
pesticide registered in the United States. Today these tablets
have found their place in IPM programs for use in very damp areas
(they can even be glued on walls). A new bait station containing
boric acid paste has been made by It Works, Inc. of Connecticut.
The product is child-resistant and contains a humectant to draw
moisture from the air and retain it, thereby increasing the
product's life. The paste can even be bought in bulk and applied
with a caulk gun or spatula.
To decrease application time, Parker Pest Control, Inc. of
Oklahoma has developed a power duster P.E.S.T.R machine that
provides even coverage of treated areas. It operates under an
adjustable pressure and charges the dust to increase
effectiveness. The machine can be bought by institutions for in-
house use, or pest control operators can participate in a license
agreement package including two machines, staff training, and
participation in national service contracts. The machines have a
life-time warranty. Continued service by pest control operators
would be needed to retreat areas that are regularly mopped or
disturbed, to monitor populations, and to communicate with
residents about the program.
d) Insect growth regulators
(1) Exposure effects of hydroprene and
fenoxycarb
It is known that insect growth regulators (IGR's) with
juvenile hormone activity cause a number of reproductive,
developmental, and morphogenetic effects against certain groups
of insects. Advantages of IGR use include low mammalian toxicity,
target pest specificity, and a mode of action which stands in
sharp contrast to that of conventional insecticides (an important
consideration given the developing resistance). The only insect
growth regulator currently registered and sold for control of the
German cockroach is the juvenile hormone analog hydroprene. This
JHA juvenilizes and sterilizes adults which had been exposed to
it as fifth stage nymphs. Fenoxycarb, another juvenile hormone
analog, has similar effects and will soon be sold for German
cockroach control. King and Bennett (1988) examined the
developmental responses of different age classes of nymphs
topically exposed to hydroprene and fenoxycarb.
Technical grade formulations of fenoxycarb (96.8 percent)
and hydroprene (96 percent) were diluted in acetone and applied
to the ventral abdomen of newly molted first-, second-, third-,
fourth-, and fifth-stage nymphs. Three replicates, ten nymphs per
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age class, were treated with either 0.01, 0.1, 1.0, 10.0, or
100.0 micrograms of each JHA. (Smaller nymphs received doses that
were actually twice those of older nymphs due to the difference
in size.) Control nymphs were treated with acetone. After
treatment, individuals were reared in separate containers and
their development monitored.
The highest percentage of mortality (76-100 percent)
occurred with the 100 and 10 microgram per microliter
concentrations of fenoxycarb administered to nymphs of stages one
through four. These percentages were significantly greater than
those caused by hydroprene and acetone. The only hydroprene
treatment that caused a mortality percentage greater than that of
the controls was 100 micrograms per microliter applied to first
stage nymphs. Apparently, more than this amount of hydroprene is
required to affect all age classes of B. germanica.
The nymphs killed by fenoxycarb exposure between the first
and fourth stage showed no signs of poisoning until the time when
controls molted to the next stage. At that point, treated nymphs
became excessively black and exhibited uncoordinated leg
movements while dn their backs. Mortality onset time was usually
the same for all nymphs per age class regardless of the
concentration used. Symptoms lasted for one to four days before
the insects died. Most nymphs died with their cuticles intact
which means that they were probably unable to undergo ecdysis.
Nymphs exposed to fenoxycarb at the fifth stage lived for around
forty-nine days after the final molt of the controls. A few
emerged as adults, but they were unable to fully shed their old
cuticle and eventually died. Researchers have theorized that
excessive quantities of JHA's or juvenile hormones lead to
ecdysone (molting hormone) deficiencies which prevent lysis of
the old cuticle. Further investigation is needed to elucidate the
mechanism behind this process.
Nymphs surviving exposure to 100 or 10 micrograms per
microliter of fenoxycarb during their fifth stages were the only
ones that exhibited significant developmental delays. Survivors
took up to nine weeks longer than controls to become adults and
were physically abnormal (e.g. twisted wings, improperly formed
sensory organs, increased melanization). It can be concluded that
fenoxycarb shows a greater lethal activity against B. qermanica
nymphs than hydroprene (probably due to differences in chemical
structures). Fenoxycarb is therefore a promising control
technique since it not only kills young nymphs but also
sterilizes adults exposed as fifth-stage nymphs. Preliminary
testing has shown that fenoxycarb can actually sterilize nymphs
at a dose much lower than that required to kill younger nymphs
(i.e. 13 micrograms per gram). Further testing should determine
whether the amount of active ingredient found in commercial
formulations is sufficient to kill as well as sterilize B.
germanica.
(2) Treatment and retreatment effects using
hydroprene
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Bennett, Yonker, and Runstrom (1986) evaluated a long-term
treatment and retreatment program of hydroprene against German
cockroaches in multi-family housing units. Existing infestations
were attributed to inadequate maintainence, general clutter, and
poor sanitation. Before the treatments began, insect populations
in the kitchens and bathrooms were visually sampled. Sticky traps
were used to evaluate existing population structures and to
determine the number of adults with twisted wings (hence,
estimate the number of late-stage exposures).
Four treatment regimens were evaluated
(initial/retreatment): 1.2 percent hydroprene / 1.2 percent
hydroprene, 0.6 percent hydroprene / 0.6 percent hydroprene, 0.6
percent hydroprene / propetamphos + 0.6 percent hydroprene, 0.6
percent hydroprene / none. Retreatments were done after three
months. A fifth treatment, used for comparison, was an initial
application of prepetamphos followed by propetamphos (a
conventional residual insecticide) retreatment. Four to six
foggers were used per apartment. The release rate for the high
and low concentrations were, repectively, 6.80 grams and 3.40
grams. The rate for propetamphos was 18.5-37.0 grams.
Posttreatment sampling occurred at one, two, three, six, and
twelve months.
For three months posttreatment, the propetamphos-only
treatment gave population reductions like the four hydroprene
treatments. But, at six months the 1.2 percent hydroprene fogger
gave a higher population reduction than the propetamphos-only
application. There was no statistical difference between the 1.2
percent and 0.6 percent fogger applications when the retreatment
was with hydroprene, but the 1.2 percent fogger gave the highest
and most consistent percent reductions over a twelve month
period. (The 0.6 percent fogger dropped in effectiveness compared
to the 1.2 percent fogger at the six month point.) Both 0.6
percent fogger treatments followed by hydroprene retreatment gave
higher reductions than a single application of the 0.6 percent
fogger. The greatest number of twisted wing adults were caught
six months posttreatment.(These last two findings indicate that
extended effectiveness is dependent on hydroprene retreatment at
three months.)
An important finding in this experiment is that the
population reduction achieved by propetamphos plus the 1.2
percent fogger was greater than two applications of propetamphos.
It is therefore more beneficial to reapply the low-toxicity IGR
than to reapply the conventional insecticide. The potential for
decreasing use of a residual insecticide of moderate toxicity
without diminishing control clearly indicates a place for
hydroprene in IPM programs. Similar benefits were observed by Ogg
and Gold (1988) using chlorpyrifos and fenoxycarb. Chlorpyrifos
was found to decrease the cockroach population significantly less
than three different levels of chlorpyrifos-fenoxycarb
combinations. The improved activity of the chlorpyrifos-
fenoxycarb combination opposed to the use of chlorpyrifos alone
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was attributed to the IGR effects induced by fenoxycarb. The
success of fenoxycarb is dependent on the ability of the
insecticide to maintain cockroach populations at relatively low
initial levels, until the IGR effects can be exerted on the
population. Further tests are necessary to determine the most
suitable insecticides for this purpose.
(3) Effects of fenoxycarb on technicians
It has been reported that the LD50 of fenoxycarb to rats is
greater than 10,000 mg/kg body weight orally, over 20,000 mg/kg
dermally, and over 480 mg/kg inhaled (four hour exposure). The
following study by Ogg and Gold (1988) is pertinent to our
discussion since was designed to measure the exposure of
technicians and the contamination of residences when three
concentrations of fenoxycarb, tank-mixed with chlorpyrifos, had
been used for control of the German cockroach.
Two experienced technicians applied fenoxycarb in three
sites in each of twenty homes. A 0.5 percent chlorpyrifos and 1
percent fenoxycarb mixture was used. In the first test, dermal
exposure of the technicians was estimated. The technicians wore a
one-piece polyester coverall with an open collar and short
sleeves, an open-mesh cap, respirator, and neoprene gloves.
Dermal exposure pads were placed on the outer clothing and all
clothing beneath the coveralls (forearm pads were directly
attached to the skin). Other pads were attached to the head,
chest, back, thigh, and just above the ankle. The pads contained
no material that would interfere with fenoxycarb detection.
After exposure, the pads were removed and subsequently
analyzed in the laboratory. The total amount of fenoxycarb found
on the pads was divided by the exposed area of the pad and the
elapsed application time to give the rate of exposure (micrograms
per square centimeter per hour). The workers washed their hands
in a bag containing 150 ml of methanol (fenoxycarb is soluble in
methanol). The total amount of fenoxycarb removed from the hands
was divided by an estimate of the total area of both hands to
give a figure for the rate of hand exposure. It was found that
the neoprene gloves received 98.7 percent of the dermal exposure
and that technician's hands should therefore be protected.
Respiratory exposure was also estimated through attachment
of an air-sampling pump to each worker. The device consisted of a
battery-powered air pump fitted with a glass sleeve that had a
polyurethane foam plug to scrub fenoxycarb from the air. The air
sampler was attached to a belt fastened around the lower back,
with one end of a Tygon tube attached to the air sampler and the
other to the inlet of the glass sleeve. The tube was attached
over the shoulder and rested on the chest in such a way as to
simulate the downward position of the human nostril. Data was
expressed as micrograms fenoxycarb per liter of air. The amount
of fenoxycarb acquired was divided by the application time and
the pumping rate (respiratory rate was assumed to be 1,740 liters
per hour). Average exposure was 0.33 micrograms per liter, a low
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value which suggests that exposure was minimal. However, no
threshold limit value has been set for fenoxycarb by the American
Conference of Governmental Industrial Hygienists (1984).
Environmental contamination was estimated by the surface
wipe sampling method at three non-target sites in each residence.
Sampling was done just prior to application, right after
application, and one day, one week, and one month after. The
sample surface was treated with methanol and scrubbed with gauze
until dry. Exposed pads were treated as in the dermal exposure
part of the study, with the total amount retrieved divided by the
sampled surface area and the application time to give an estimate
of the contamination rate. Fenoxycarb was detected only right
after application. At all other times there was no evidence of
the IGR (the reason for this "decrease" is unknown). Means were
as follows (micrograms per square centimeter per hour): 0.32
(kitchen counter), 0.41 (kitchen floor), and 5.22 (bathtub).
The total dermal plus respiratory exposure was equal to
21.16 rag/hour for a technician wearing "full garb". The
respiratory exposure was 1.565 mg/hour. It can generally be
concluded from this study that under the stated conditions, the
application of 1.0 fenoxycarb causes no significant risk to
either the technician who mixed and applied the chemical or to
the residents of the treated stucture. Normal work apparel
including gloves appeared sufficient as a barrier to skin
penetration. It is also advised that residents not be allowed
into the residence during application and that exposure be
reduced by ventilating treated areas.
e) Photodynamic dyes
It has been reported that American and Oriental cockroaches
become moribund when they are exposed to light after
internalizing rose bengal or erythrosin B (xanathene) dyes.
Recently, Ballard, Vance, and Gold (1988) explored the light and
dark reactions of the German cockroach and the brown-banded
cockroach after being fed rose bengal and erythrosin B.
German cockroaches were used in the first phase of the
experiment. Each dye was administered in a 1 percent sucrose
solution and 5 x 103 M concentration to males, females, and
nymphs kept in dark confinement chambers. Mortality was recorded
at twenty-four hour intervals for 92.5 hours. At that point,
lights were turned on and mortality readings were taken each half
hour for the first hour and a half, then hourly for six hours.
In another test, adult male German cockroaches were given
free access to the two dyes at these concentrations: 1 x 103 M, 3
x 103 M, or 5 x 103 M in 1 percent sucrose. Mortality was
recorded daily for six days. Ten survivors were removed from each
container, anesthetized, weighed in a dimly lit room, and
returned to their container. One control group was given the dyes
but was not weighed to indicate the mortality associated with
handling and exposure to" dim light. In the other control the
subjects were given 1 percent sucrose but no dye, and then put
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through the weighing procedure. This provided information on
mortality due to intake of the dye and also provided baseline
data on population weight for untreated cockroaches.
It was found that all the subjects were affected by the
dyes when administered at the initial concentration, but
mortality associated with the light-independent reaction was
greater for adults than nymphs. The erythrosin dye was more toxic
to all the subjects during the dark phase of the experiment and
for the first 2.5 hours of light exposure. Male and female
mortality increased for two hours after the onset of light, with
nymphs responding more slowly to the light-dependent effects of
the dye than adults did. There was significant light-independent
weight loss among cockroaches given rose bengal at 3 x 103 M and
erythrosin B at 5 x 103 M.
Brown-banded cockroach nymphs were used in the second phase
of the experiment. Dyes, in the above trio of concentrations,
were administered to the nymphs which were confined in glass
bottles. One control population was given the sucrose solution
alone as food. Mortality was assessed at twenty-four hour
intervals for 144 hours, after which time the subjects were
exposed to light. Mortality was then assessed every half-hour
until 146.5 hours had passed. The other control was given the
dyes but kept in the dark for 146.5 hours. Mortality results for
the brown-banded nymphs were consistent with those seen for th©
same concentrations in German cockroaches. Over time, mortality
was greater with erythrosin B than with rose bengal during the
light-independent reactions (for all concentrations). Light-
dependent effects increased mortality during the 2.5 hours of
light exposure.
It was concluded that both photodynamic dyes cause
mortality in German and brown-banded cockroaches and that light-
independent weight loss due to dye exposure occurred in male
German cockroaches. Light-dependent mortality was observed for
both species of cockroach. The use of these dyes as control
measures has been investigated under field conditions using flies
(Musca spp.) and fire ants (Solenopsis germinata (S.)). The
feasibility of using these dyes needs to be pursued, particularly
since erythrosin B has an acute oral LDSo in rats of over 7,000
mg/kg.
f) Anacardic acid
Dr. Isao Kubo, a chemist at the University of California at
Berkeley, has isolated a chemical (anacardic acid) from root bark
of the African Msimbwi tree which has potential use for the
control of cockroaches. In the early 1980's, insect physiologists
at Berkley found that injecting E2 and F2 prostaglandins
(chemical messengers) into crickets (taxonomically similar to
cockroaches) caused them to lay eggs. This chemical was believed
to be passed by the male to the female during mating to stimulate
egg-laying. When asked to look for prostaglandin presence in male
crickets, Kubo could not find any even though the biochemical was
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easily isolated in fertilized females. It was then suspected that
the males injected into the females not the biochemical itself,
but something that caused its manufacture in the females.
Prostaglandin synthetase, an enzyme present in male crickets, was
found to initiate and accelerate creation of prostaglandins from
a precursor in the female. From these findings, it was postulated
that a form of insect control could be worked out if the enzyme
in the males might somehow be suppressed, consequently preventing
egg-laying in the female.
Kubo recalled that, in Africa, loads of the cashew fruit
tree are dumped into ponds to inhibit mosquito larvae. Also, that
the root bark of the Msimbwi tree can be used to induce abortion.
The active ingredient in both these cases was found to be
anacardic acid. Research was continued with the crickets,
witheach sex being injected with the substance. In male
spermatocytes a decrease in synthetase content resulted; in
fertilized female eggs there was a reduction in prostaglandin
content. Kubo found that without a sufficient quantity of
prostaglandin to stimulate the smooth muscles of the female's
egg-laying apparatus, eggs could not be passed. Interpretation of
these findings in light of control mechanisms spells potential
use of anacardic acid in a bait, or in the form of a spray or
powder that can be absorbed through the exoskeleton. Kubo
disclaims commercial potential at this time but is planning
large-scale experimental trials with the chemical.
3. Biological control of cockroaches
a) Use of a hymenopterous oothecal parasitoid
Cockroach natural enemies include other insects, arachnids,
nematodes, and vertebrates, but possibly the most important are
the hymenopterous oothecal parasitoids. Since these organisms are
small and actively search for hosts they represent a promising
mechanism of control for urban pests.
Coler, Driesche, and Elkinton (1984) reported the effect of
the oothecal parasitoid Comperia merceti (Compere) on a
population of brownbanded cockroaches (S. longipalpa (F.j). An
existing cockroach infestation was repeatedly sampled over the
course of three years using baited glass jar traps. About a year
into the sampling period, the cockroach population was
artificially stimulated by supplemental feeding. This "outbreak"
was used to evaluate the effect of the parasitoid. After each
sampling period, the traps were examined and the specimens
divided into five categories: adult males, adult females, and
three classes of nymphs. "Catch" was the number of each category
caught per trap per day- Trapped cockroaches were released back
into the infested room from which they were captured.
Parasitoid activity in the infested room was measured by
exposure of cockroach oothecae which had been provided by a
laboratory-reared colony of brownbanded cockroaches. The oothecae
had been laid on paper toweling and were about three and a half
days old. Strips were cut from this toweling and hung in
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locations in the infested room where the invading cockroaches had
previously deposited oothecae. After one week of exposure, the
eggs were taken back to the laboratory and raised individually
under atmospherically controlled conditions until all parasitoids
and cockroaches emerged.
Results, based on the number of parasitoids emerging per
ootheca or the proportion of oothecae attacked, indicated that
there were no statistically significant differences in the
parasitoid's preference for oothecae of different ages. (Implied
is that an appropriately aged group of oothecae had been used as
subjects; further, that it is possible to view the entire
oothecal stage as somewhat susceptible to attack.) Parasitism was
minimal when cockroach densities were low and did not increase
until after the cockroach population was stimulated. Later in the
study, the degree of parasitism dropped sharply before leveling
out for the duration of the study. The resultant decrease in
cockroach density (and corresponding drop in trap catch)
paralleled the increase in parasitism and manifest itself first
at the nymph level then at the adult level. Initially, the
youngest class of cockroaches dominated. With time, the age
structure became inverted as is characteristic of a declining
population whose nymph number is depressed. Later, surviving
nymphs came to represent the adult segment of the population. The
initial population structure was eventually regained but all
stages were present at a lower density-
This study clearly indicated the ability of C. merceti to
suppress populations of S. longipalpa (L.). This conclusion was
supported by the inverse relationship between the degree of
parasitism and the cockroach population, and also by the changes
in the age structure of the cockroach population. However, the
directly proportional relationship between parasitism and
oothecal density suggests that the effectiveness of the
parasitoid may be limited to only high^density host populations
(unless a mass release of parasioids is used against a cockroach
population of low density). The researchers acknowledged
difficulties associated with rearing and supplying live organisms
(parasitoids) but also stated that some pesticide-sensitive areas
(zoos, pet shops, laboratories) may find this sort of biological
control preferable to the use of conventional insecticides.
b) Potential use of fungi
Although over 750 species of fungi have been described as
entomopathogenic, less than ten have been used as biological
agents of control. Twenty-five species of Herpomyces are host-
specific parasites of the cockroach cuticle but none have
deleterious effects on the host. Few intestinal fungal parasites
exist and reports on pathogenic fungi of cockroaches are not
available.
However, one fugal infection occurring in a laboratory
colony of B. germanica has been studied by Archbold and others
(1986). A reliable source of the infection was maintained by
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transferring uninfected cockroaches from a control colony to the
infected colony. Live infected cockroaches were collected
periodically and categorized according to instar, behavior,
activity, and general appearance. Early signs of the disease were
hard to distinguish, although later symptoms included
sluggishness, premature adult death, and predominance of nymphs.
The best external symptom was brittle and curled antennae.
Internal presence of infection was indicated by yeast cell
presence in the hemolymph. Infected individuals usually died
upright, with their legs stiffened in a paralytic posture
suggestive of nerve or muscle dysfunction. Retarded movement and
loss of coordination often preceded death. Additional stresses
such as carbon dioxide, anesthesia, food and water deprivation,
and insecticidal treatment caused increased mortality.
In insects, hemolymph circulates by tidal flow through
muscle contraction, pumping of the dorsal aorta, and through
pumps located at the base of the legs and antennae. Inadequate
blood circulation due to the number of yeast cells in the
hemolymph could have resulted in poor nutrient supplies reaching
the antennae and other appendages. The pathology of the disease
is associated with a high number of yeast cells, and high titers
are associated with the appearance of the characteristics
mentioned above. The symptoms were followed by a decrease in
activity and, within thirty days post infection, death.
Verrett and others (1987) noted a similar infection in a
laboratory colony of American cockroaches (P. americanum). The
researchers described in detail certain physical changes and
identified the infecting organism as a form of Candida. Damage
done by the yeast involved the host granulocytes (one of the two
main types of hemocyte in the American cockroach). Nuclei of
infected cells were found to be indented and nuclear membranes
raised near the yeast cell. Host cell nucleoplasm had
disintegrated and little cytoplasm was present. Damage to the
cockroach hemocyte is thought to be due to a toxin, a potentially
potent agent for penetrating the insect and digesting its tissue
or hemolymph. The action of the enzyme (canditoxin) in C.
albicans (not the species isolated in this study) is believed to
inactivate proteins by interfering with vital physiological
functions. The mechanism may involve a slowing or cessation of
the flow of transmitter substances in motor neurons.
Cockroaches mount an immune response by either
phagocytosing or encapsulating yeast cells. Encapsulation occurs
when hemocytes encounter "non-self" surface characteristics and
release intracellular granules which have a chemokinetic effect
on neighboring hemocytes. Resultant adhesion of the cells forms
the first layer of the capsule. Other cells are similarly
recruited which causes an increase in layer formation. use
of the biological agent found in P. americanum as a control is
not feasible at this time, but it is possible that a
physiologically different strain could be developed. However,
because sibling species are human pathogens, development would
have to precede with great care. Use of the organism even in
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baits may still subject humans to the disease agent through food
exposed to cockroach droppings. These studies did serve to
elucidate the mechanism behind cockroach immunity (an important
advance when this and other yeast infections are considered) and
to advance the study of a potentially viable method of cockroach
control.
4. Physical control of cockroaches
a) Household measures
Harborages can be washed, vacuumed, or steam-cleaned to
eliminate egg cases, fecal material, and accumulated bits of
food. Vacuumings should be burned, deeply buried, placed in
sealed containers, or composted after the infested area is
disinfected with ammonia. Outdoor populations can be reduced by
moving debris from around the building. In general, physical
methods of combat (including swatting or stomping on adults) are
relatively unimportant in a cockroach management program unless
they are directed at trespassers in uninfested areas.
b) Ultrasound
The use of ultrasound devices to control pests was widely
publicized in the early 1980's, but research on its use for
agricultural and urban purposes has been limited. In response to
the public's continuing requests for information and because
previous laboratory tests have detailed responses to pure tones
emitted by non-commercial devices, Ballard, Gold, and Decker
(1984) investigated the effectiveness of a commercial frequency-
modulated ultrasound device (Pest Guard).
The device required a 120 V AC, 60 Hz power source and
supposedly swept through a range of 30-65 kHz. Eight plywood test
cubes were caulked and white^washed to maximize sound refection
and were fitted with the device in an upper corner. The cubes
also had a pitfall trap opposite the device to catch moving
cockroaches. A significant increase in movement (hence trap
cdtch) occurred in cubes with active devices, but habituation
occurred in six to seven days. No significant difference in daily
mortality existed between control and active-device cubes (this
was consistent with the manufacturer's claim that the device did
not actually kill the insects). In essence, the cockroaches
continued to exist in the structure even though a decrease in
their visibility may have occurred in "treated" areas. The
advantage to simply increasing cockroach movement within a
structure is somewhat difficult to see.
Koehler, Patterson, and Webb (1986) evaluated the
ultrasound produced by nine different devices in an effort to
determine their ability to control German cockroaches. Using two
unfurnished rooms connected by a corridor, the researchers set up
an acoustic gradient which permitted the cockroaches to
voluntarily enter or exit "noisy" areas. While it was found that
almost all the devices did put out alternating high frequency
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sounds, placement of furniture in the treatment room
significantly reduced the sound pressure level. There was no
predominant movement of the cockroaches to untreated rooms. In
fact, it was found that cockroaches were just as likely to enter
treated as well as untreated rooms. Monthly trap catches showed
that the German cockroach population had not significantly
decreased through use of the devices. In fact, twenty-four hours
after some devices had been returned to the lab, eight nymphs
emerged. The cockroaches were obviously using the devices as a
harborage and were clearly not repelled by them. Manufacturer
claims were generally considered unfounded given the observed
lack of repellency and the reduction in ultrasound intensity
caused by the presence of furniture.
c) Zap Trap™
A relatively new trap, manufactured by Bi-Pro Industries,
Inc. of California, contains a lure and an electrified grid that
jolts the attracted cockroaches onto a disposable sticky surface.
The device can hold up to three thousand cockroaches. The lure (a
secret formula probably containing a female sex pheromone)
attracts all major cockroach species. Lures are replaced every
one to two months and cost about six dollars. A powerful glue on
the trays can hold even larger cockroaches like the American and
smokeybrown. The devices generally require an electric outlet but
some are battery-powered.
The trap can be used alone in less densely infested or
localized areas, or when a client prefers not to use conventional
insecticides. Ed Brown of International Roach Busters of
Massachusetts combines these traps with boric acid treatments.
The traps catch sluggish cockroaches and essentially buy time for
the slower-acting boric acid.
B. Mulligan of Simon Fraser University in Vancouver,
British Columbia has shown in field and lab tests that
cockroaches are more attracted to Zap Trap™ than conventional
traps without lures. This attraction aspect, along with the fact
that the trap is effective over a 2,500 square foot area suggests
that cockroaches may be lured from up to 30 feet away. The trap
is particularly useful in wet areas where boric acid cannot be
applied. Unfortunately, the trap costs over three hundred
dollars; some pest control operators offer lease-buy options.
5. The Asian cockroach: new control problem
The Asian cockroach Blattella asahinai, a recent arrival in
Tampa, Florida, has proceeded to take up residence for six
hundred miles around. Infestations of 90,000 to 165,000 per acre
are common. Compared to the German cockroach, the Asian cockroach
prefers lit areas (e.g. light-colored exteriors, turned-on
television sets) and also flies. Richard Brenner, an entomologist
at the USDA Agricultural Research Service in Gainesville,
Florida, says that Asian cockroaches follow you from room to room
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until the last light is turned off, at which point they head for
moist areas such as damp towels. Given their range in Asia, these
cockroaches could exist as far north as Maryland on the east
coast and as far as Washington on the west coast. In regards to
control, the USDA has no jurisdiction since the Asian cockroach
is not a plant pest. The Florida Department of Health also waives
responsibility since no valid cases of endangerment have been
reported.
II. Wood-boring beetles
A. Identification of the problem
Wood-boring beetles, when considering the damage they cause
in the United States, are next in importance to wood-rotting
fungi, termites, and carpenter ants. An estimate for the annual
loss due to repairs and wood-replacement caused by lyctid beetles
is several million dollars. Three main factors have contributed
to this species' pestiferous habits. One is the increase in
demand for imported hardwoods. The tropical origin of some of
these woods permits lyctid activity year-round, and the tropical
woods themselves (e.g. banak, obeche, lauan/meranti) have
attractively large pores and high starch content. Often,
unprotected wood must be stored in the open due to shipping and
processing delays. The second factor relates to the difficulty of
recognizing infestations. Eggs are small and deposited in the
wood, and adults may not emerge for about a year. Damage may not
be apparent for a long time. The third factor concerns cargo
containerization, a practice which restricts inspections at entry
ports. Sine© an infestation may be considered by APHIS (USDA
Animal and Public Health Inspection Service) to be impossible to
quarantine, infested materials may be allowed to enter our ports.
Some beetles can cause extensive damage, but identifying the
species, determining whether or not larvae are present, and
evaluating the extent of the damage are the most sensible steps
to follow before initiating treatment.
B. Biology of wood-boring beetles
1. Introduction
The first step in controlling wood-boring beetles is to
identify the infesting species. Two general categories can be
constructed: those that can reinfest wood and cause extensive
damage, and those that cannot reinfest wood and cause damage only
for the existing generation. There are three important families
of reinfesting beetles: true powderpost beetles of the family
Lyctidae, furniture and deathwatch beetles of the family
Anobiidae, and the old house borers, a member of the family
Cerambycidae. Infestations of other beetles are often over by the
time they are detected. "Non-reinfesters" generally enter the
house within wooden objects or lumber used in construction. When
adults emerge from the wood, they die and infestation ceases.
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Emergences may occur for a period of weeks or months but should
not be mistaken for reinfestation.
2. Lyctid beetles
Lyctid beetles are the most widespread reinfesters in the
United States, readily attacking furniture and structural wood
components. Under natural conditions, lyctids overwinter in the
larval stage. When spring comes, larvae bore closer to the
surface of the wood, and make a cocoon-like structure or pupa.
Two to three days later, after emerging as adults and mating, the
females lay their eggs in the surface of the wood (namely the
sapwood of hardwoods with large pores for depositing eggs). The
most susceptible woods are hardwoods such as oak, hickory, and
ash. Less susceptible species include walnut, pecan, poplar,
sweetgum, and wild cherry. Wood species that are "immune" include
certain softwoods (cedar, fir, pine, and spruce) and certain
hardwoods (basswood, beech, and birch). A wood moisture content
(WMC) between 8 and 32 percent is required for oviposition. Most
activity is associated with 10-20 percent WMC which is typical of
that found in many buildings.
Females lay an average of twenty to fifty eggs in exposed
tree parts and milled lumber. At first, hatched larvae bore
straight tunnels into the wood, but later the larvae paths criss-
cross and become irregular. Flour-like frass can be found in the
tunnels. Larvae emerge from the wood through circular exit holes
1/32-1/16 inch in diameter the following spring. Adults are 1/8
to 5/16 inches long, somewhat flattened, and light brown to black
in color. Generally, life cycles are completed.in nine to twelve
months, but development can be hastened if temperature and wood
starch content are favorable. With a starch content of 0.3
percent, a temperature between seventy and ninety degrees
Fahrenheit, and humidity between 70-90 percent, life cycles can
run between three and ten months. If these variables are all low,
development can take as long as four years. Larvae grow fastest
when the WMC is 14-16 percent.
Larvae cannot digest cellulose. Attack is solely to
sequester starch contained in the plant material. Prior to egg-
laying, females "taste-test" the wood to determine if it has a
suitable starch content for the larvae. Eggs will not be laid
where the starch content is below 3 percent. Wood recently dried
through a kiln-drying (not air-drying) process is preferred for
its higher starch content. (Old wood does not have a high starch
content.)
3. Anobiid beetles
In general, the deathwatch and furniture beetles of the
United States require more moisture than lyctids do. Hence, they
are more problematic in coastal areas, unheated buildings, and
where humidity is high. Contrary to what is implied by their
common names, these beetles find furniture too dry to infest.
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Some anobiids will attack hardwoods and softwoods, old or new.
Sapwood is their basic food and they have the ability to digest
cellulose due to the presence of yeast cells in their digestive
system. Anobiids live on bark-free scars of trees or dead limbs,
but are found in the house in humid crawl spaces.
Females use small cracks and crevices in the wood for egg-
laying. When the larvae emerge from the eggs, they bore a little
ways into the wood, then make a sharp ninety degree turn,
proceeding in the direction of the woodgrain. As the larvae grow,
so do their tunnels, becoming packed with fecal material (a fine
powder with conspicuous elongated pellets). Eventually the
tunnels intersect, and the wood disintegrates into a mass of
fragments. Two to three years are needed for complete larval
development, but dry conditions encountered during this time can
draw out the development process and possibly kill the young. In
the spring, larvae widen part of one tunnel and bore an exit hole
(circular, 1/16-1/8 inch). Mates are sought and the cycle begins
again. Adults are 1/16 to 3/8 inch long with their heads hidden
beneath a hood-like thorax. Many females lay their eggs in the
wood from which they have just emerged.
4. Cerambycids (the old house borer)
Old house borers (Hylotrupes banulus) do not need a bark
covering on the wood that they infest. Females lay their eggs in
crevices in the wood and emergent larvae often wander about until
they find a suitable place to bore into the wood. Once inside,
they remain near the surface, gradually going deeper as they
grow. Old house borers do not attack heartwood. The larval stage
can be completed in two to three years but can take as long as
fifteen if the wood is very dry (as in attics). Tunneling in dry
wood proceeds slowly, and the tunnels are characteristically
marked by ring-like striations and tightly packed coarse frass.
Unlike the anobiids, old house borers do not need yeast in their
guts to digest cellulose. Adults, 1/3 to 2 inches in length,
remain in the tunnels for some time prior to emergence and mating
in mid-to-late summer. Exit holes are oval or round and species-
dependent in size. Because emergence may be staggerd over a
period of years, these beetles often appear to be doing more
damage at a faster rate than is really the case. Temperature has
been the primary factor limiting their spread in the United
States.
5. Non-reinfesters
Non-reinfesters are responsible for attacking weakened
forest trees. Larvae (grubs) remain in these trees through
milling and emerge later as adults. Some beetles lay eggs within
the bark of freshly-cut trees. If the wood is not cured, or cured
improperly, larvae-infested wood can be used in homes, with
emergence occurring after construction. Beetles may come through
ceiling beams, subflooring, hardwood floors, and wall plaster.
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Non-reinfesting beetles include flathead borers (Buprestidae),
most roundheaded borers (Cerambycidae), and bark and timber
beetles (Scolvtidae). Reinfestation is impossible for these
beetles unless bark, the cambium layer, or the living sour sap
xylem of the wood is available for egg-laying. Since none of
these parts are found within structures, non-reinfesters are
unable to survive and die without laying eggs.
C. Detection
Aside from beetle presence, infestations can be detected by
the appearance of exit holes and fecal pellets. These two
characteristics are helpful in identifying the invading species.
The following considerations should be made: the size and shape
of the exit holes, whether the damage is to hardwood or softwood,
whether the wood is old or new (all of the beetles discussed here
will infest new wood, only three of the reinfesting type will
attack old wood), and the type of frass found in the tunnels.
Identifications can be confirmed by a Cooperative Extension
Service entoitiolog"ist.
Inspections for wood-boring beetles should be performed
yearly, in conjunction with the inspection for termites, keeping
in mind all the "hot spots" listed in our discussion of termite
detection. Things to look for include entrance and exit holes,
sawdust or wood fragments, and weakened, hollow-sounding wood. It
should be emphasized that discovery of these things does not
necessarily imply that an active infestation is present. "Used"
wood may not be suitable for later generations, and environmental
conditions may inhibit survival. The presence of fresh fr.ass and
living beetles should be used to determine activity. In some
species (e.g. old house borers), chewing can be heard inside the
wood. Assessment of the damage caused by reinfesting beetles can
be difficult to determine, possibly not until damaged wood has
been removed.
As in detection of termites and (potentially) carpenter
ants, dogs can also be trained to increase the accuracy of
detecting infestations by wood-boring beetles. Their keen sense
of smell and hearing as well as their size enable them to detect
infestations overlooked by pest control operators.
D. Prevention
1. Inspection
There are six main ways to prevent the occurence of wood-
boring beetles in the home. The first involves inspection of wood
and wooden items before they enter the house. Small holes,
sawdust, and tiny wood fragments are key signs of a potential
problem. Antigues and imported wooden craft items are likely
culprits. Exposing the items to extreme heat or cold will
basically solve the problem.
2. Sealing wood surfaces
i i
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Sanding and coating susceptible woods is a preventative
technique that works well against lyctids. Varnish, shellac, and
paint fill pores in the wood, hence eliminate desirable egg-
laying sites for females. The most susceptible locations are
unpainted storage containers or other wood items around the
house. If such items are made of a softwood such as pine,
infestations are unlikely since lyctids prefer large-pored
hardwoods such as oak, ash, hickory, mahogany, and bamboo. The
furniture beetle also avoids sealed surfaces.
3. Reducing available moisture
Adequate ventilation and drainage around a building tend to
reduce the moisture content of the stucture's wooden members, and
in so doing decreases the chance of beetles finding suitable wood
sources. Particular attention should be paid to this aspect of
prevention in areas where humidity is high and where winters are
warm. Homes that are centrally-heated and remain so for extended
periods of time are less susceptible than other residences to
attack by beetles. Vacation homes are often sites of damage
because heating periods are not prolonged and because tight-
sealing permits high levels of moisture in the wood.
4. Storing firewood outdoors until it is needed
Firewood brought into the home may already be infested with
powderpost beetles. It is suggested that piles of firewood be
kept outdoors, the largest the farthest away, and smaller ones
nearer the home. Wood scraps should not be allowed to accumualte
around the house and should be burned regularly.
5. Debarking stored logs
Additional protection of stored wood is afforded when the
wood is debarked. Some beetles need bark to start tunneling and
egg-laying. (Elm owners might already be aware that debarking elm
before storage prevents infestations by the beetles that cause
Dutch Elm Disease.)
6. Using kiln- or air-dried lumber
Using kiln- or air-dried lumber seems to be the best and
least expensive preventative measure that can be taken. Drying
processes kill many sorts of beetles, including all stages of
lyctids. It should be noted that drying schedules are based on
the thickness of the largest piece of lumber in the given load,
not on initial wood moisture content. Kiln sterilization of
finished products may damage glue joints, and it is important to
remember that this process does not necessarily prevent
reinfestation.
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7. Using boron compounds
Another preventative measure being studied is the treatment
of unseasoned (undried) wood by dip-diffusion with boron
compounds such as TIM-BORR (disodium octaborate tetrahydrate)^
AM-BOR-SR (ammonium pentaborate-sodium sulfate), and AM-BOR-P
(ammonium pentaborate-sodium phosphate. The dip-diffusion process
must be performed at the mill since it.depends on the wood's own
moisture content to facilitate diffusion of the preservative into
the wood. Sapwood should be completely penetrated after dipping
and no further treatment should be required, even after the wood
is processed.
In a series of experiments conducted through the USDA
Forest Service, Southern Forest Experiment Station, investigators
used banak wood in a dip-diffusion process aimed at preventing
lyctid beetle infestation. Banak wood refers to about forty
Central and South American species in the genus Virola. The wood
is imported from native regions and used in the United States for
millwork, moldings, and picture frames. Slow water transport of
logs and other hold-ups between felling and delivery to markets
in the States often leads to degradation of the wood by ambrosia
beetles and fungi. But, more important to United States
consumers, processing delays also permit lyctid beetle
establishment and spread through non-infested wood or newly-
manufactured products. Products can be widely distributed during
the year or more before exit holes of these beetles are seen,
paving the way for complicated lawsuits and sundered business
relations.
The researchers have determined the dip-time, solution
temperature, and diffusion storage period that provideds the best
dip-diffusion treatment. They have also found that loading (the
amount of borate on wood available for diffusion after dipping)
is affected by wood surface characteristics, dip time, solution
temperature, concentration, and agitation (to keep the borates
suspended). Wood surface characteristics and wood moisture are
probably the primary variables since high borate concentrations
can compensate for short immersion times. Factors found to affect
the rate of diffusion include the wood species, wood density and
thickness, ambient temperature and relative humidity, and length
and manner of storage.
Other researchers have found that boron content in the
center of treated boards doubles with a rise in ambient
temperature from forty-five to sixty-five degrees Fahrenheit.
Diffusion processes conducted in tropical regions should
therefore proceed at a faster rate due to high relative humidity
which maintains the moisture content in freshly-cut wood. It has
also been found that the diffusion rate is not greatly affected
by a 60 percent WMC, but that the diffusion time nearly doubles
when the moisture content is reduced to 40 percent.
In commercial treatments, loosely-packed, partially
stickered packets of freshly-sawn wood are immersed for
approximately one minute in a 25 percent boric acid equivalent
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solution of polyborate and maintained at 130 degrees Fahrenheit
by steam heat. Dipped boards are then stacked with stickers for
seven days under a protective roof to allow the borate to diffuse
into the wood. About 1.6 percent sodium pentachlorophenate can be
used in the solution to prevent mold growth during the diffusion
period, (pre-planing the wood before making wood products removes
the mold growth inhibitor). An estimated thirty-nine pounds of
polyborate can be used per thousand board feet, at a chemical
cost of two cents per board foot (1985 prices) .
Results obtained from boron treatments indicate that they
afford protection against L. brunneus (Stephens), the eastern
subterranean termite R. flavipes (Kollar), and the brown-rot
decay fungus G. trabeum. Although bacterial symbionts have not
been found in L. brunneus, they have been found in L. linearis
Goeze and it is believed that boron kills lyctid larvae and
termites by eliminating their intestinal digestive symbionts.
Wood containing over 0.3 percent BAE (boric acid equivalent) of
sodium borate is protected from R. flavipes (Kollar) and wood
containing over 0.5 percent BAE is protected from G. trabeum. An
undefined level less than 0.2 percent BAE is required to protect
banak from L. brunneus. Treatments do not protect against mold
fungi or soft-rot decay fungi.
The dip-diffusion process is appealing since boron-treated
wood is not hazardous to its users and because treatment quality
can easily be monitored by color-testing and hydrometer readings
of the treatment solution. One man using a forklift can treat a
days production in several hours. Dip-diffusion with boron
compounds is a more cost-effective process than fumigation and
replacement of damaged areas, and is also less expensive than
pentachlorophenol and mineral spirit treatments used for
moldings. Although boron salts are known to make wood brittle,
one lumber company has reported no problems in shaping the
moldings that they maufacture. It is also possible that treated
scraps can be used in particle board. A bonus of the procedure is
that it increases resistance to combustion. Less environmentally-
sensitive alternatives to sodium pentachlorophenate are being
investigated for use in the treatment solution. The major
drawback of the process is that treated wood must be protected
from leaching either by using it above-ground and protected by a
roof or by finishing the wood with paint or a water-repellent.
E. Control
1. Chemical controls
a) Fumigation
Fumigation is the most common type of chemical control of
wood-boring beetles. It involves draping an infested structure
with a plastic sheet and using the highly toxic gas methyl
bromide to impregnate the wood. Residents must vacate the
premises for two to three so that the fumigant can sufficiently
dissipate. Fumigating limited areas has not proven terribly
successful. As stated previously, fumigation is an undesirable
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alternative due to its high cost, use of highly toxic chemicals,
and temporary benefit. Although sulfuryl fluoride is also used as
a fumigant, it is not effective at killing the eggs of lyctids.
To compensate for this, the material is often used at a high
dosage and at an added expense.
Chlorpyrifos is commonly used for spot-treatments of
infested wood. It acts against adults that need to chew their way
out of the wood and against larvae that emerge from the eggs laid
on it. Chorpyrifos capitalizes on the fact that many wood-borers
lay their eggs on the same wood that they emerged from. Surface
spraying with lindane was once widespread, but it is no longer
used. Some operators have experimented with injecting
insecticides into infested wood. Because this treatment is
costly, not thorough, and its results rather unpredictable, it is
not recommended. Using pressure-treated lumber when replacing
wood is an alternative, particularly for areas that are
continually wet.
b) Pyrethrum
TriDie™ is a dust combination of a silica aerogel and
pyrethrum that can be applied into and around exit holes of
reinfesting beetles. The mixture can also be blown into wall
voids, attics, and crawl spaces. Beetles are first killed by the
pyrethrum, but when this ingredient has dissipated, the silica
gel takes over as a residual insecticide that can kill beetles
which emerge later by abrading their protective covering and
prompting dehydration. Torpedo™ is another product, considerably
less toxic than methyl bromide, which has permethrin as its
active ingredient. A 0.1 percent solution has been shown to be as
effective at controlling L. brunneus as lindane and chlordane,
and the organophosphate fenitrothion. Synthetic pyrethroids are
known to reduce egg-laying without killing adults and are also
known to have a repellent effect (a technique which would prevent
reinfestation). Spot treatment are a practical solution to the
risks associated with fumigation.
2. Physical controls
a) Coating exterior surfaces
Beetle infestations can be physically controlled by
replacing damaged wood, altering moisture and temperature levels
around wooden structural members, and by treatment with the
Electrogun™. Frequently, the best solution for beetle
infestation is removal of damaged wood, since many of the wood-
boring beetles do not reinfest the wood after they have emerged.
However, reinfesters should be deterred by painting and
varnishing exterior surfaces and by following the preventative
measures outlined above.
b) Temperature and humidity variation.
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Deathwatch beetles and old house borers are very
susceptible to heat, changes in temperature, and lack of
moisture. The deathwatch beetle Anobium puctatum, found in both
Europe and the United States, can only enter wood that has
already been partailly predigested by fungi. Laboratory studies
have indicated that the old house borer does not do well when
temperature and humidity fluctuate. Wood blocks containing larvae
were placed in the attic, basement, and laboratory areas of a
building in Virginia. Growth was inhibited in the attic when
temperatures reached seventy-five degrees Fahrenheit and relative
humidity as between 66 and 86 percent. In the laboratory, it was
found that the larvae did best at eighty-six degrees Farenheit
and about 82 percent relative humidity. The potential for using
temperature and humidity changes as a form of control has been
discussed under termite and carpenter ant control. Vapor
barriers, ventilation, and central heating may even preclude the
use of more elaborate physical methods of control.
c) Electrogun™
Use of the Electrogun™, explained in previous sections, is
also effective at eliminating infestations of wood-boring
beetles. Because the device leaves no harmful residues, is safe
for the operator to use, and presents no hazard to the occupants,
this technique is easily incorporated into least-toxic management
programs. It is particularly suited to areas in which infested
wood members (e.g. paneling) cannot be removed or replaced.
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Johnson, Jeffrey. "Roaches I Have Known." Environmental Action
(March/April 1986): 16.
King, J.E. and G.W. Bennett. "Mortality and Developmental
Abnormalities Induced by Two Juvenile Hormone Analogs on
Nymphal German Cockroaches (Dictyoptera: Blattelidae) Journal
of Economic Entomology 81 (1) (February 1988): 225-227.
Koehler, Philip G., Richard S. Patterson, and J.C. Webb. "Efficacy
of Ultrasound for German Cockroach (Othoptera: Blattellidae)
and Oriental Rat Flea (Siphonoptera: Pulicidae) Control."
Journal of Economic Entomology 79 (4) (August 1986): 1027-
1031.
Koehler, Philip G. , Richard S. Patterson, and Richard J. Brenner.
"German Cockroach (Orthoptera: Blattellidae) Infestations in
Low-Income Apartments." Journal of Economic Entomology 80 (2)
(April 1987): 446-450.
La Page, Jeffrey P. and Lonnie H. Williams. "Lyctid Beetles
Recognition, Prevention, Control." Circular No. 106, Lousianna
State University and Agricultural and Mechanical College,
Center for Agricultural Sciences and Rural Development, (March
1979): 2-11.
Levit, Stephen. "The Pest Pill." (Crosscurrents) -Science (May
1986): 62-63.
Ogg, Clyde and Roger E. Gold. "Exposure and Field Evaluation of
Fenoxycarb for German Cockroach (Orthoptera: Blattellidae)
Control." Journal of Economic Entomology 81 (5) (October
1988): 1408-1413.
Olkowski, Helga. "Gencor-New Roach Control Product." Common Sense
Pest Control Quarterly II (2) (Spring 1986): 21-23.
Olkowski, William and Sheila Daar. "Boric Acid: New Formulations
and Application Equipment." The IPM Practitioner IX (6-7)
(June/July 1987): 3-4.
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Olkowski, William, Helga Olkowski, and Sheila Daar. "Controlling
Wood-Boring Beetles in Buildings." Common Sense Pest Control
Quarterly I (3) (Summer 1985).
. "IPM for the German Cockroach." The IPM Practitioner VI
(3) (1984): 7-10.
Olkowski, William. "New Cockroach Trap for IPM Programs." The IPM
Practitioner VIII (4) (April 1986): 5-6.
"Powder-Post Beetles." (The Pennsylavania State University,
Cooperative Extension Service) (February 1981).
Runstrom, Erik S. and Gary W, Bennett. "Movement of German
Cockroaches (Orthoptera: Blattellidae) as Influenced by
Structural Features of Low-Income Apartments." Journal of
Economic Entomology 77 (2) (April 1984): 407-411.
Schal, Goby. "Relation Among Efficacy of Insecticides, Resistance
Levels, and Sanitation in the Control of the German Cockroach
(Dictyoptera: Blattellidae)." Journal of Economic Entomology
81 (2) (April 1988): 536-544.
Scott, Jeffrey G., Sonny B. Ramaswamy, Fumio Matsumura, and Keiji
Tanaka. "Effect of Method of Application on Resistance to
Pyrethroid Insecticides in Blattella germanica (Orthoptera:
Blattellidae)." Journal of Economic Entomology 79 (3) (June
1986): 571-575.
U.S. Department of Agriculture. Forest Service. Integrated
Protection Against Lyctid Beetle Infestations Part I.- The
Basis for Developing Beetle preventative Measures for Use by
Hardwood Industries, by Lonnie H. Williams. New Orleans:
Southern Forest Experiment Station.
. Research Note Integrated Protection Against Lyctid
Infestations Part II.- Laboratory Dip-Diffusion Treatment
of Unseasoned Banak (Virola spp.) Lumber with Boron Compounds,
by Lonnie H. Williams and Joe K. Maudlin. Washington, D.C. :
U.S. Government Printing Office. 1985.
"Unwelcome Immigrant: The Asian Cockroach." Discover (March 1987):
10.
Verrett, Joyce M., Karen B. Green, Lester M. Gamble, and Fred C.
Crochen. "A Hemocoelic Candida Parasite of the American
Cockroach (Dictyoptera: Blattidae)." Journal of Economic
Entomology 80 (6) (December 1987): 1205-1212.
Wileyto, E. Paul and Mallory Boush. "Attraction of the German
Cockroach, Blattella germanica (Orthoptera: Blatellidae), to
Some Volatile Food Components." 76 (4) (August 1983): 752-756.
Williams, Lonnie H. and Joe K. Maudlin. "Integrated Protection
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Against.Lyctid Beetle Infestations. III. Implementing Boron
Treatment of Virola Lumber in Brazil." Forest Products Journal
36 (11/12) (November/December 1986): 24-28.
Williams, Lonnie H. and Terry L. Amburgey. "Integrated Protection
Against Lyctid Beetle Infestations. IV. Resistance of Boron-
Treated Wood (Virola spp.) to Insect and Fungal Attack."
Forest Products Journal 37 (2) (February 1987): 10-17.
Williams, Lonnie H. and Jeffrey La Fage. "Tracking the Lyctid
Beetle." Southern Lumberman 239 (2968): 112.
Zungoli, Patricia A. and William Robinson. "Feasibility of
Establishing an Aesthetic Injury Level for German Cockroach
Pest Management Programs." FORUM: Environmental Entomology
13 (6) (December 1984): 1453-1458.
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RELATED ADVANCES: BACULOVIRUSES AND THE NEEM TREE
I. Baculovirus and the viral enhancing factor
II. Neem: a new frontier
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RELATED ADVANCES: BACULOVIRUSES AND THE NEEM TREE
I. Baculovirus and the viral enhancing factor
Recently, attention has focused on the use of viruses as a
form of pest control and it is possible that a suitable indoor
application may eventually be found. Five hundred species of
baculovirus are able to infect specific lepidopteran species.
However, they do not act against mammals, plants, or other
insects. When a baculovirus enters the larval host it quickly
replicates, bloating the host with billions of virus particles
each wrapped in a protective protein coat. The commercial
usefulness of this type of infection is that these viruses can be
genetically manipulated to cause the manufacture of certain
"desired" protein products. For example, removal of the coat-
protein gene from the viral DNA and attachment of its promoter to
a chosen gene causes larval cells that possess the altered virus
to produce large quantities of the "new" gene's product.
When a caterpillar feeds on a leaf and ingests a
baculovirus, the alkalinity of the insect's stomach dissolves the
virus's protein coat, allowing it to traverse the stomach wall
and enter mid-gut cells. Within about ten hours, the viruses have
replicated and filled these cells. In another two hours,
infection production is at a maximum. After twenty-four hours the
baculoviruses have again become packaged in their coats. The
replication and packaging processes continue for approximately
five days, at which time an infected caterpillar may be seen
hanging from its perch, distended with virus particles that
represent half its volume. When the larva dies and decomposes,
the encased viruses are released. Protected from dessication and
ultraviolet light by their protein coats, the viruses can remain
on foliage for up to ten years.
While the baculovirus is a newcomer to genetic engineering,
it has long been recognized as a natural insecticide. For
example, it has been noted that sudden drops in populations of
gypsy moths are often due to baculovirus epidemics. The EPA has
approved use of four unaltered baculoviruses for control of the
gypsy moth, cotton bollworm, European pine sawfly, and Douglas-
fir tussock moth. Alan Wood and Anthony M. Shelton, virologists
at Boyce Thompson Institute for Plant Research at Cornell
University in Ithaca, New York, have created a baculovirus which
persists in the environment for only a few days and is hence
environmentally safe. The researchers stripped the baculovirus
Autoarapha californica of its polyhedrin coat by deleting the
aene that codes for it. The "naked" baculovirus was then mixed
with a wild-type strain. Through a process called co-occlusion
the wild-type viruses manufactured enough polyhedral coats to
clothe the deficient particles. The resulting deficient strain
was thus able to mimic the wild-type strain in appearance and
enter its host (the cabbage-looper). The cycle ends at that
point since mimic descendents cannot produce protective coats
,- A ••
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and are degraded. Furt,her testing of these short-lived
baculoviruses has been pursued.
Robert R. Granados, also a virologist at Boyce Thompson,
has discovered a protein in another cabbage-looper baculovirus
(the Trichoplusia ni granulosis virus or TnGV). The coat protein
has been called a viral enhancing factor (VEF) and is able to
bore holes directly through the lining of the cabbage-looper's
stomach, blasting a path for entry of the virus. Effects of the
VEF have been found to be more dramatic in the TnGV than in A.
californica. The VEF permits a 25- to 100-fold increase in the
amount of kill compared to use of the virus alone.
There are four ways that the VEF gene could be used for
pesticide purposes. First, it could be combined with a
baculovirus known to attack a given crop-pest, then formulated
into a spray and applied to susceptible crop plants. Second, the
effectiveness of the protein might be enhanced through insertion
of one or more copies of the gene coding for it into the TnGV-
Third, new viral insecticides produced through genetic
engineering of other baculoviruses can also be endowed with
enhanced effectiveness through the protein's activity. Fourth,
insertion of the VEF gene into the genome of certain crop plants
could make the insects that feed on these plants more vulnerable
to viruses as well as bacteria, fungi, and maybe chemical
insecticides. The bacterium Bacillus thuringiensis, fatal to
insects, has already been found effective when used in this
manner and it is possible that even this bacterium could be
improved through incorporation of the VEF gene. Although this
type of research is not directly applicable to household pests,
it is possible that future developments may lead to indoor
applications.
II. Neem: a new frontier
Margosan-O™ is the first neein oil extract registered as
an insecticide for non-food crops in the United States. It is a
product of the neem tree Azadirachta indica which has a number of
properties that act synergistically to control pests. The tree
exhibits a low mammalian toxicity, can grow in arid "waste"
sites, can be used as a windbreak and shade tree, and can also be
used as fodder for domestic animals. In India, neem products have
been used in toothpaste, in Pharmaceuticals, and as grain
protectants. Unfortunately, its versatility is slowing down
registration procedures and its potential is not well known
amongst pest control operators. Studies are being pursued in
India, Israel, West Germany, the Phillipines, Togo, East Africa,
and the United States. Six avenues are being followed:
Preparation of extracts, chemistry of extracts, modes of action,
formulation of products, laboratory and field studies of effects
against certain pests, and development schemes.
Neem tree products can act as broad spectrum repellents,
anti-feedants, growth regulators, and toxicants. So far, at least
J ( •
' G.
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123 insect, 3 mite, and 5 nematode species are affected by varies
neem extracts. (The German cockroach is included in this group.)
Powdered seeds suspended in water are effective against a number
of pests, as is neem oil which is extracted from the seed kernel
through the use of solvents. Oil extraction residues and pulp can
be made into "neem cake" which has insecticidal and fertilizer
properties when added to rice paddies. Leaves are used as
repellents to protect woolens and grains, and leaf mulch can be
used as a protectant or fertilizer (although its high protein
content makes it better for animal food). Timber from the neem
tree has been found to be resistant to termites and wood-boring
beetles, and is useful as fenceposts, in buildings, and in
furniture. The neem tree bears fruit in five years, is fully
productive in ten, and lives for over two hundred. Thirty to
fifty kilograms of fruit could be produced annually per tree.
That coverts to 6 kg neem oil at a projected dollar per kilogram.
The rest would be used in cakes valued at a little over twelve
dollars.
Ethanol extracts from the seeds are safe to use on non-food
crops and the following figures tell why its registration should
extend to other uses. The acute oral toxieity of the extracts in
mouse tests was very low (13,000 mg/kg) and no skin sensitivity
was noted in guinea pigs injected with neem extracts. Neemrich
100, a formula with 30 percent neem oil, applied dermally to
albino rats at daily doses of 600 mg/kg for three weeks, resulted
in no overt toxieity or behavioral abnormality. A Neemrich I
formulation gave an LD50 of 11,220 mg/kg (oral in rats) and other
studies have shown that concentrations as high as 8,500 mg/kg
(oral) were still not toxic to rats.
The most important ingredient in neem extracts is
azadirachtin, a feeding deterrent found in the seed kernel.
Ethanol extractions of this chemical from one hundred grams of
neem seeds varies, but the greatest yield (4-5 percent) has been
obtained using an azeotrophic mix of methyl tertiary-butyl and
methanol. Precise description of the modes of action of various
neem tree products is difficult due to the complex and
synergistic action of the biologically active ingredients. Many
active ingredients aside from the one mentioned exist and
modalities have been shown to depend on the type of extract, the
test insects, geographical origin of the extract, dosages, and
formulations. Margosan-O™1 s manufacturer estimates that it would
cost up to 1.2 million dollars to complete the tests required for
registration of the material for use on food crops. Small,
innovative companies would find this a great impediment to
marketing. It has been suggested that a less stringent
registration procedure be applied, one that could be used for
other low-toxicity products.
The "Neemrich" concept, proposed by researchers at the
National Chemical Laboratory of India, refers to standardized
extracts capable of being made through small-scale extraction
processes at the village level. The recommended process has five
steps and requires inexpensive solvents. Neemrich I will be the
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first agent of this sort to be registered, but Neemrich II and
Neemrich III are being developed. Neemrich advocates believe the
active ingredient should not be described chemically, and should
instead be defined biologically or according to its activity.
Neem-based insecticides are well-suited for IPM programs
both for food crops and within structures since the oil is not
toxic to humans or the natural enemies of pests. Development of
neem proucts challenges not only regulatory agencies but also the
petrochemical industry. Further, the neem tree is not the only
botanical pesticide that could be grown and processed locally (a
reported 2121 plant species have pest control properties). Neem
products may represent a new generation of pesticides, with
their level of effectiveness dependent on their formulations
(e.g. as spot treatments rather than for blanket coverage).
Indiscriminant use could destroy the potential of neem products,
resulting in their classification with synthetic pyrethroids and
other petroleum-based products which have lost their
effectiveness due to target-pest resistance.
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BIBLIOGRAPHY
Lewis, Ricki. "Baculovirus for Biocontrol and Biotech A Scourge
of Silkworms Becomes a Boon to Biotechnologists." Bioscience
39 (7) (July/August 1989): 431-434.
"New Protein May Increase Viruses' Insect^Killing Ability."
Lancaster Farming, 1 April 1989, 2(C) 4(C).
Olkowski, William. "Update: Neem — A New Era in Pest Control
Products?" The IPM Practitioner IX (10) (October 1987): 1-8-
. r.
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SUMMARY
A variety of control methods for termites, ants, fleas,
ticks, and beetles have been reviewed in this discussion. However,
when "across the board" effectiveness and minimal hazard levels in
and around buildings are considered, three basic types of control
stand out: desiccating dusts, temperature extremes, and insect
growth regulators. The first two target moisture requirements and
the need for a tolerable temperature range. The last one focuses
in the molting process. It appears that when direct control tactics
need to be employed, those that alter the most basic physiological
processes are often the least-toxic and most effective.
Desiccating dusts include diatomaceous earth, silica dust
(amorphous precipitated silica or silica aerogel), and boric acid
dust. Each is long-lasting, exhibits low mammalian toxicity, and
can be used in confined areas at various times during construction.
Boric acid has a distinct set of advantages. For example, it can
be formulated to be non-volatile, electrically charged, and anti-
caking. Its coloring and bitter taste also act to discourage
ingestion by children or pets. Moreover, boric acid is non-
repellent (when properly applied), cost-effective, and has not
caused the development of resistance in target pests. Marketing
advances include more effective application equipment and water-
resistant formulations.
The use of liquid nitrogen and extreme heat have been found
to be effective against a number of wood-infesting insects as well
as other pests that can be confined to treatment sites. Both
techniques are relatively inexpensive and environmentally benign.
Unfortunately, a good deal of overkill is sometimes required to
ensure treatment success and a detailed description of effects on
household items is unavailable.
Insect growth regulators (e.g. methoprene, hydroprene, and
fenoxycarb) act against termites, ants, and cockroaches. They are
biologically specific, exhibit low mammalian toxicity, and cause
a number of effects in insects, including the assumption of soldier
and soldier-like characteristics, loss of symbionts, failure of
colony establishment, egg mortality, and sterility. Insect growth
regulators can be combined with other less-toxic controls such as
boric acid or with conventional insecticides to either hasten pest
population reduction or to increase the effectiveness of an
instituted control program. Properly clothed technician experience
little risk during application, at least when exposed to
fenoxycarb.
All three of these methods aim at eliminating existing pest
populations from a given area, not at excluding or repelling them.
Desiccating dusts and insect growth regulators can remain effective
for extended periods although neither presents the hazards
associated with the residues of conventional insecticides. It
should be emphasized however that least-toxic control programs are
founded on the presence of preventative measures, mainly habitat
modification and elimination of attracting resources. Use of the
dip-diffusion process for wood for example is a very appealing
option in the prevention process since it is long-lasting,
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relatively easy to perform, and cost-effective. Research supports
the use of many of the direct and indirect control measures
outlined in this review. But, it seems that pest control operators.
industry, and the general public will need to be willing to make
certain compromises before alternative techniques are more broadly
integrated into least-toxic control programs.
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50272-101
REPORT DOCUMENTATION
PAGE
1.REPORTNO.
EPA/101/F-90/003
PB99-256447
4. Title and Subtitle ,
Least Toxic Pest Control: How Infestations of Termites, Ants, Fleas, Ticks and Beetles can be
Controlled Without Causing Short-or Long-Term Air Quality Changes and Health Risks
5. Report Date
Completed Fall 1989
7. Author(s)
Lynda M. Murray
8. Performing Organization Rept No.
10. Project/Task/Work Unit No.
9. Performing Organization Name and Address
Rutger University
Biology Department
Camden,NJ. 08102
11. Contract(C) or Grant(G) No.
(C)
(G)
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
Office of Cooperative Environmental Management
499 South Capital Street, SW A-101-F6
13. Type of Report & Period Covered
Technical Report
14.
15. Supplementary Notes
16. Abstract (Limit: 200 words)
1405 - Least Toxic pest control: How Infestations of Termites, Ants, Fleas, Ticks, and Beetles can be Controlled Without Causing
Short- and Long- Term Indoor Air Quality Changes and Health Risks
The report is part of the National Network for Environmental Management Studies under the auspices of the Office of Cooperative
Environmental Management of the U.S. Environmental Protection Agency.
A number of least-toxic measures are discussed within the framework of integrated pest management systems for termites, ants,
fleas, ticks, and beetles. It is presumed that adherence to such programs minimizes changes in indoor air quality and also reduces
health risks by eliminating use of traditional, often hazardous pesticides. Emphasis is placed on preventative measures such as
habitat modification and resource removal to eliminate conditions that encourage the establishment of and foster the growth of pest
populations within the home. Control tactics are broadly categorized as chemical, biological, and physical, and are detailed in light
of pertinent advances in research. Techniques relate directly to the biology of the organisms and target periods of vulnerability,
symbiotic relationships between the pest and other organisms, and basic physiological processes. Boron formulations, insect
growth regulators, and the use of extreme temperature seem to have the most widespread applications, although "neem" products
may soon surpass even these advances
17. Docuement Analysis a. Docuement Discriptors
b. Identifier's/Open-Ended Terms
c. COSATI Field/Group
18. Availablllity Statement
19. Security Class (This Report)
20. Security Class (This Page)
(SeeANSI-Z39.18)
21. No. of Pages
22. Price
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