APPLY PESTICIDES CORRECTLY
A GUIDE FOR COMMERCIAL APPLICATORS
AQUATIC
PEST CONTROL
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDE PROGRAMS
WASHINGTON, D.C. 20460
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TABLE OF CONTENTS
Page
Acknowledgments 1
Preface 1
Introduction 2
Aquatic Weeds 2
Weed Control 2
Control without Pesticides 2
Biological Control 3
Control with Pesticides 3
Application Techniques 3
Weed Control in Static Water 4
Weed Control in Large Impoundments .. 5
Weed Control in Flowing Water 5
Weed Control in Limited-Flow
Waterways 6
Vertebrates 6
Fish 6
Mammals 6
Other Vertebrates 7
Environmental Considerations and
Restrictions 7
Units and Conversion Equivalents 8
1976
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ACKNOWLEDGMENTS
PREFACE
This guide has been developed by California State
Polytechnic University, Kellogg West Center, under
U.S. Environmental Protection Agency (EPA) con-
tract number 68-01-2918. This contract was issued
by the Training Branch, Operations Division, Offfice
of Pesticide Programs, EPA. The leader of this
group effort was Eugene D. Young, California State
Polytechnic University, Kellogg West Center. Editors
were Mary Ann Wamsley, EPA, and Donna M.
Vermeire, North Carolina State University.
Contributors were:
Al Burkhalter, Florida Department of Natural Re-
sources
William E. Currie, U.S. Environmental Protection
Agency
Peter A. Frank, U.S. Department of Agriculture
Rex E. Marsh, University of California—Davis
W. B. McHenry, University of California—Davis
Richard F. Moorer, U.S. Environmental Protection
Agency
Donald E. Seaman, University of California—Davis
Richard Zuccarini, Amvac Chemical, Los Angeles,
California
Federal regulations establish general and specific
standards that you must meet before you can use
certain pesticides. Your State will provide material
which you may study to help you meet the general
standards.
This guide contains basic information to help you
meet the specific standards for applicators who are
engaged in aquatic pest control. Because the guide
was prepared to cover the entire nation, some in-
formation important to your State may not be in-
cluded. The State agency in charge of your training
can provide the other materials you should study.
This guide will give you information about:
• recognition and control of aquatic pests, and
• environmental concerns in aquatic pest control.
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INTRODUCTION
The demand for water resources for recreational,
agricultural, industrial, and other purposes is in-
creasing. Many kinds of plant and animal aquatic
pests can interfere with these and other water uses.
Control of aquatic pests is of national importance
as a means of protecting these uses for the public.
The information in this manual applies to control of
aquatic pests in:
• recreational waters used for fishing, boating, and
aquatic sports,
• agricultural reservoirs and water distribution
channels used for stock-watering, irrigation, and
drainage,
• ornamental ponds,
• coastal bays, estuaries, and channels, and
• drinking water reservoirs.
Effective management of aquatic pests requires the
combination of all appropriate control methods,
including:
• mechanical,
• cultural,
• biological, and
• chemical.
AQUATIC WEEDS
The first step towards prevention or control of aqua-
tic weeds is to identify them correctly. Most con-
trol methods are aimed at specific weeds or at
groups of weeds with similar growth habits. Aquatic
weeds can be grouped as follows:
• Emersed aquatic weeds—weeds that grow stand-
ing out of the water, or in water-saturated soils.
Examples are cattails, bulrushes, and arrowheads.
• Submersed aquatic weeds—weeds that grow under
the water surface. Examples are pondweeds,
naiads, coontails, and watermilfoils.
• Floating aquatic weeds—weeds that float on the
water surface. Examples are duckweeds, water-
hyacinth, waterlettuce, waterferns, and water-
lilies.
• Algae—weeds without true stems, leaves, or
vascular systems. Examples are waternet, pitho-
phora, and chara.
Many of these plants may be pests in some situa-
tions and desirable plants in others, depending on:
• their abundance and
• the use of the water they inhabit.
WEED CONTROL
CONTROL WITHOUT
PESTICIDES
Pond and Ditch Design
Proper design and construction of ponds is an im-
portant factor in preventive control of weeds. Shal-
low water at the margins of ponds provides an
ideal habitat for emersed weeds, such as cattail.
Submersed weeds can easily become established
there and then spread into deeper water. Banks
should be sloped steeply so that there is very little
water less than 2 or 3 feet deep.
Proper design and construction of ditches and chan-
nels makes weed control easier in the future. If the
banks are leveled and smoothed, hard-to-reach places
will be eliminated. Lining canals will help in alleviat-
ing water weed problems.
Mechanical Control
It may be necessary to use mechanical methods to
control submersed weeds. Sources of water for
drinking, for livestock, and for fish ponds often
cannot be treated with chemicals.
• Chaining may be practical in some instances, par-
ticularly in canals.
• Drag lines are useful for cleaning canals and
margins of lakes and ponds.
• Weed mowers are used in both canals and lakes
for cutting weeds.
Some mowers simply cut the weeds loose beneath
the water surface. Others (aquatic weed harvesters)
collect the weeds for removal from the water. Dis-
posal of harvested weeds is often a problem. Most
methods of mechanical control fragment the weeds.
This may actually aid in the spread of most species
of weeds, since they may reproduce from the pieces.
Mechanical control is usually slower and more
costly than control of the same weeds with chemicals.
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Draining and Drying
Some ponds, lakes, canals, and ditches may be
drained so aquatic weeds will dry. The water levels
in some large lakes and reservoirs may be lowered
enough to expose weeds in shallow areas. Drying
periods of several months may be needed to control
weeds in some ponds and lakes. In canals, it may
not be practical to interrupt water flow for longer
than 3 or 4 days. The season of year and species
of plant present may determine whether this method
will be useful in a particular situation.
Be sure to consider the resident fish species and
their normal spawning times.
Fertilization
Fertilization with inorganic nutrients may be a con-
venient and inexpensive method for control of weeds
in ponds and small lakes. Fertilization stimulates
a dense bloom of microscopic algae. The algae shade
the pond bottom and prevent or reduce the growth
of submersed weeds. Unless the fertilization is done
correctly, however, the weed problem may become
even more severe.
The fertilizer may be applied broadcast, applied
from a boat, or dissolved in the water in other ways.
Existing weeds either are not affected or their growth
may be stimulated. You may need to remove them
before fertilizing. Ponds that have a monthly water
exchange greater than the capacity of the pond do
not respond well to fertilization. Fertilizers are
more effective in deep water than in shallow water.
BIOLOGICAL CONTROL
Biological control is not often used. It has been suc-
cessful in several situations. Biological control
agents include:
• Tilapia—This plant-eating fish has only limited
value. It will eat aquatic plants and reproduce
rapidly, but it survives winter temperatures in
only a very few areas of this country.
e White amur—The white amur is a large fish that
eats large amounts of aquatic plants. It survives
well in many areas of the United States. Because
its environmental hazards are not fully known
only a few States permit its use.
• Insects—Several insects have been brought into
this country to control aquatic weeds. The most
successful are a beetle and a moth that are
parasitic on alligatorweed. They have provided
good control of this weed in large areas of the
South. Other insects are under study for control
of other species of weeds.
CONTROL WITH PESTICIDES
Chemicals used in aquatic weed control are classified
as herbicides. Herbicides used primarily for control
of algae are called algicides, even though they may
also kill other aquatic plants. Aquatic herbicides are
available in several formulations:
SPRAYABLE FORMULATIONS—Most herbi-
cides are formulated to be mixed with a water car-
rier and sprayed. Some perform best as aquatic
herbicides when applied into static or flowing water
so that they disperse evenly and contact underwater
surfaces of weeds. Kinds available are:
• water-soluble powders or crystals that form true
solutions in water,
• wettable powders that can be suspended in water
and applied,
• water-soluble liquid concentrates that form true
solutions in water,
• emulsifiable liquid concentrates that form ordinary
"oil-in-water" emulsions in water, and
• special liquid concentrates that form "water-in
oil" emulsions (called invert emulsions) when
mixed with water and oil in the spray tank or
when applied through special mixing nozzles.
GRANULAR FORMATIONS—Many aquatic her-
bicides are used as dry granules of various sizes.
Kinds available are:
• granulated pure chemical, such as crystalline cop-
per sulfate,
• granules or larger-size pellets of clay and other
materials impregnated with active ingredient, and
• slow-release granules or pellets designed to re-
lease the active ingredient in small amounts over
an extended period of time in the water.
Application Techniques
Four zones of a body of water may be treated:
• the water surface,
• the total water volume,
• the bottom 1-to 3-foot layer of water, or
• the bottom soil surface.
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SURFACE TREATMENT—Generally only V4 to
1A of the surface area of the water should be
treated at a time. This helps protect fish from a
possible shortage of oxygen; Surface acreage of a
rectangular body of water equals length in feet times
width in feet divided by 43,560.
TOTAL WATER VOLUME TREATMENT—The
whole body of water (from the surface to the bot-
tom) is treated. .Or you can treat 1A to Vz of the
total water volume (based on surface area) at a time.
Calculate the volume of the body of water and add
chemical to obtain the required dilution in the
water.
The concentration of chemical needed to kill aquatic
plants is often very small and is stated in parts per
million (ppm).
If the toxicity level of a certain chemical for a par-
ticular aquatic weed is 2 ppm of active ingredient,
for example, the chemical should be applied at a
ratio of 2 parts of active ingredient to 1 million
parts of water in the area to be treated.
First, calculate the acre-feet of the body of water
to be treated. Multiply surface acres by the average
depth in feet. An acre-foot of water weighs 2.7
million pounds. If one dissolves 2.7 pounds of any
material in 1 acre-foot of water, there will be a
concentration of 1 ppm by weight (ppmw). Use the
following formula to determine the material needed
to obtain a desired ppm concentration:
2.7 Xppm wantedXacre-feet=lbs. required
Assume one wants to treat a pond containing 10
acre-feet. The concentration of active ingredient re-
quired is 0.5 ppm. Using the formula:
2.7X0.5X10=13.5 Ibs. of active ingredient
BOTTOM LAYER TREATMENT—Treating the
deepest 1 to 3 feet of water is especially useful in
deep lakes where it is impractical to treat the entire
volume of water. Such treatments are generally
made by attaching several flexible hoses at 3- to
5-foot intervals on a rigid boom. Each hose is
usually equipped with some type of nozzle at the
end. They may be weighted to reach the depth
desired. The length of hose and speed of the boat
carrying the application equipment also affect the
depth of application. Successful bottom treatments
apply the herbicide as a "blanket" in the lower 1
to 3 feet of water.
BOTTOM SOIL TREATMENT—Herbicide appli-
cations may be made to the bottom soil of a drained
pond, lake, or channel.
Weed Control in Static Water
Static water is water in ponds, lakes, or reservoirs
that has little or no inflow and outflow. Even
totally enclosed bodies of water often have appre-
ciable water movement because of wind and other
factors. Weeds commonly grow in static water
up to 12 feet deep. In very clear water, however,
weeds sometimes grow in water 20 feet or more
in depth.
FLOATING AND EMERSED WEEDS
Sprayable formulations are almost always preferred
for floating and emersed weeds. These weeds are
killed by direct foliage applications of the spray
mixture:
• by aircraft,
• with ground equipment, operated from the bank
if the pond is small, or if weeds occur only around
the margins, or
• from a boat, using various types of booms or
spray guns.
SUBMERSED WEEDS AND ALGAE
Herbicide formulations for control of submersed
weeds and algae in static water may be sprays or
granules.
Sprayable Formulations—Herbicide sprays are most
often applied as water-surface treatments, particu-
larly in shallow water. The herbicide is dispersed
throughout the water by diffusion, thermal currents,
and wave action. Sprayable herbicides can be ap-
plied under the surface by:
• injection through a hose pulled along behind a
boat, or
• injection into the water by booms.
In all instances, control of the weeds depends on
good dispersion of the chemical in the water.
Sprayable herbicides sometimes are used for bottom
soil treatments.
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Some sprayable herbicides may be applied from air-
craft at low volumes of 5 to 10 gallons per acre.
Both surface and injection treatments made by boat
or ground equipment are more effective and are
easier when larger volumes of liquid carrier are
used. A handy sprayer for making applications by
boat uses a special pumping system that draws water
from the lake or pond as the boat moves along.
Concentrated herbicide is metered into the pumped
water to achieve the concentration required. This
avoids both frequent interruptions to prepare spray
solution and the need to carry water on board.
Granular Formulations—The main aquatic use of
granular herbicides is for control of algae or sub-
mersed weeds, although some are effective on cer-
tain emersed weeds. Because granules sink to the
soil surface, they perform about the same way as
herbicides applied as bottom soil treatments. Ap-
plication rates for granular herbicides may be based
on:
• amount of herbicide per unit of surface area, or
• the concentration (ppm) that would be achieved
if the same amount of herbicide were dissolved
and totally dispersed in the water (total water
volume treatment).
Granular herbicides perform best when distributed
evenly over the water surface. They may be broad-
cast by hand or manual spreader over small areas.
Special granule spreaders mounted on aircraft or
boats are used for large scale applications.
Advantages of granular herbicides are:
• treatment is usually confined to the bottom where
the submersed weeds are,
• they can be made to provide a long contact time
with weeds (slow-release granules),
• the herbicide concentration can be held to a low
level, and
• they make it possible to use chemicals that in
other formulations would be toxic to fish.
Weed Control in Large Impoundments
Herbicide applications that are successful in smaller
bodies of water often perform poorly in large im-
poundments. These impoundments often have much
water movement caused by thermal currents or the
wind.
Weed control may sometimes be improved in these
sites by:
• using the maximum recommended application
rates,
• treating relatively large water areas at one time,
• applying herbicides only during periods of mini-
mum wind,
• using bottom treatments in deep water,
• using granular formulations when possible, and
• selecting herbicides that are absorbed quickly
by the weeds.
Weed Control in Flowing Water
Aquatic weeds in flowing water are the most diffi-
cult to control. Because the water is moving from
one location to another, the possible hazards of
herbicide use are greater.
Herbicides are sometimes used to control weeds in
natural streams. Control of aquatic weeds in man-
made water distribution and drainage systems is
more common. Most of these carry irrigation water.
Do not irrigate crops with treated water unless per-
mitted by the herbicide label. Some systems also
carry domestic, industrial, and recreational water.
As the number of water uses increases, more re-
strictions and precautions are required.
FLOATING AND EMERSED WEEDS
These weeds, when in flowing water, require the
same herbicides and treatment techniques as they
do in static water. Precautions and restrictions are
the same as those for control of submersed weeds
in flowing water.
SUBMERSED WEEDS AND ALGAE
Effective control of these weeds can be achieved
in flowing water only by continuously applying
enough herbicide at a given spot to maintain the
needed concentration and contact time.
The greater the cross sectional area of the stream
and the greater the speed of flow, the larger the
volume of water that must be treated.
The large volume of water that must be treated
makes the use of herbicides in flowing water costly,
particularly when:
• the weed infestation covers only a small area, or
• the herbicides are effective for only a short dis-
tance downstream.
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Few herbicides are available for control of sub-
mersed weeds in flowing water. The more common
ones are:
• Copper sulfate, used to control algae. It is toxic
to trout at recommended treatment rates, but
only moderately toxic to most other fish species.
The toxicity of copper to fish increases with de-
creased total alkalinity of the water.
• Grade B xylene and acrolein, which are highly
toxic to fish and many other forms of aquatic
life. They are used primarily in water delivery
systems that contain no fish, or where the water
delivery is far more important than the value of
the few fish that might be present.
Be sure that the residues in the treated water and
runoff water are at or below the levels permitted
for all subsequent uses.
Weed Control in Limited-Flow
Waterways
Flood drainage canals, sloughs, and drains are good
examples of limited-flow waterways. Weed control
methods in these systems of little water movement
are very similar to those used in static water. Con-
sider the possible contamination of water used for
other purposes when you plan the use of herbicides
in limited-flow water. In some areas, drainage water
may flow directly on to cropland or be used for
irrigation, or it may enter a fishery or drinking
water supply.
VERTEBRATES
FISH
Some species of fish are considered pests in certain
areas and' situations. The major kinds of pest fish
are:
• those that compete with more desirable fish for
food, space, and other necessities of life,
• those that affect man's interest or livelihood, and
• those that prey or feed upon more desirable fish.
Control
The control of pest fish varies with each situation
and species. Some problems are not serious enough
to justify any action. In other situations, control is
necessary and can be justified on sound biological
grounds. Some pests may also be protected game
fish, so control methods that do not harm the pest
species may be the only legal solution.
NONCHEMICAL CONTROL includes temporary
draining of small bodies of water or using physical
methods such as traps, net or screen barriers, or
barrier dams.
CHEMICAL CONTROL requires the use of pisci-
cides. The use of fish control chemicals is a highly
specialized area of pest control. Few chemicals are
registered for this purpose. Use special care when
applying them.
MAMMALS
Rodents are of the most concern. They include:
• beaver,
• nutria,
• muskrats, and
• rats.
Damage includes:
• burrowing, which structurally weakens earthen
dikes, levees, and dams; causes water losses or
flooding; and increases erosion of banks,
• increasing suspended sediment in water,
• clogging culverts or water pipe intakes with vege-
tation cut during feeding or nest-building activi-
ties, and
• blocking stream flow.
Control
Depending on the pest species and the situation, the
following control methods may be used:
NONCHEMICAL CONTROL, including:
• modifying or controlling habitat, such as con-
trolling weeds to reduce food supplies,
» installing dike protectors or barriers,
• trapping, or
• shooting.
CHEMICAL CONTROL, including the use of:
• repellents,
• fumigants, and
• baits.
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Other Vertebrates
A few birds, reptiles, and amphibians may cause
some problems in local areas. Chemicals are rarely
used to control them.
ENVIROMENTAL
CONSIDERATIONS
AND RESTRICTIONS
Incorrect application of herbicides in water may
involve serious hazards to man, wildlife, fish, and
desirable plant life. Consequently, you must:
• select the correct herbicide for a specific aquatic
site and particular weed infestation,
• apply it correctly at recommended rates,
• observe the restrictions on use of the treated
water,
• be aware of the adverse effects of incorrect use,
and
• obtain permission if necessary from appropriate
State or Federal agencies.
The control of aquatic vegetation presents special
problems, because:
• the water often has multiple uses and
• herbicides will not always remain where they are
placed.
Consider all the uses of the water to be treated,
including those far downstream. Read the label to
determine that the herbicide you choose is com-
patible with these uses.
Types of water uses to consider before applying
herbicides include:
• human use, such as drinking, cooking, and swim-
ming. Few tolerances have been established for
herbicide residues in such water. Copper sulfate
has been used for control of algae in drinking
water for many years and is permitted at the
concentration of 1 ppm copper ion. Limited
residues of several other herbicides are per-
mitted in raw drinking water. However, you should
avoid contaminating any drinking water with any
level of herbicide.
• livestock and wild animal use,
• irrigation,
• industrial uses, and
• fish production—Most aquatic herbicides are not
toxic to fish or other animal life at the concen-
trations recommended for weed control. Notable
exceptions are Grade B xylene, acrolein, and
some solvents and emulsifiers in certain formula-
tions of normally nontoxic herbicides. These
should not be used in fisheries, or where the
water treated with these herbicides could enter
fishery waters.
It is possible to use these herbicides for treat-
ment of small plots, or for treatment of weed-
infested marginal areas, with little hazard to fish.
If given an avenue of escape, fish will leave
areas where the herbicide is used.
Trout are especially susceptible to copper sul-
fate. Trout waters should not be treated with
copper sulfate without consulting fish biologists.
Application Rates
Correct application of herbicides to aquatic situa-
tions involves equipment calibration and calcula-
tion of appropriate water volumes or areas. Environ-
mental hazard can result from the incorrect applica-
tion rate.
Excessive application can cause:
• damage to fish, either from direct toxicity, or
from lack of oxygen caused by an excessively
rapid kill of plants. Bacterial contamination re-
sulting from decay of killed fish might further
contaminate downstream water supplies.
• the need for exclusion of livestock from use of
the water for a longer time than necessary, and
• water unfit for irrigation use.
State and Federal Regulations
Many States have regulations which govern the
use of pesticides in water. Check with the appro-
priate agency when in doubt. There are also strin-
gent Federal and some State regulations controlling
the importation of exotic fish or plants.
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UNITS AND CONVERSION EQUIVALENTS
1 acre = 43,560 sq ft
1 acre-foot (A-ft=43,560 cu ft=325,872 gal = 2,720,000 Ib of water
1 cu ft per second (cfs) = 450 gallons per minute (gpm)
1 cu ft = 7.48 gal = 62.4 Ib of water
1 gal =128 fluid ounces = 8.33 Ib of water
1 part per million by volume (ppmv) = Igal per million gal of water
1 part per million by weight (ppmw) = 8.33 Ib of chemical per million gal of water
1 ppmw= 2.72 Ib of chemical per A-ft of water gal of liquid formulation required
Ib ai required
Ib ai per gal of concentrate
Ib ai required X100
Ib of dry formulation required =
% ai in formulation by weight
(ai = active ingredient)
FORMULAS FOR HERBICIDE APPLICATION TO CHANNELS
cfs = cross section area in sq ft X average velocity in ft per second (fps)
Cross section area of rectangular channel in sq ft = average width in feet times the average depth in ft
gal of chemical X 1,000,000
ppmv=
cfs X 450 X minutes applied
ppmv X 450 X minutes applied
gal of chemical per cfs =
1,000,000
ppmv X 450 XcfsX minutes applied
Total gal of chemical required =
1,000,000
Ib of chemicalXI,000,000
ppmw=
cfs X 3744 X minutes applied
gal of formulationXlb ai per galx 1,000,000
ppmw= —
cfsX 3744 X minutes applied
ppmw X 3744 X minutes applied
Ib of chemical per cfs =
1,000,000
ppmw X 3744 X minutes applied
gal of formulation per cfs=
Ib ai per galXI,000,000
FORMULAS FOR HERBICIDE APPLICATION TO PONDS OR LAKES
Volume of pond in cu ft=surface area in sq ft X average depth in feet
Volume of pond in A-ft=surface area in acres X average depth in feet
volume of pond in cu ft
Volume of pond in A-ft=
43,560
gal of 100% active ingredient
PDmv= ———
volume in A-ft X 0.33
Total gal of chemical required=A-ft X ppmv X 0.33
Ib ai of chemical applied
ppmw= —
volume in A-ftx2.72
Total Ib ai required = A-ft X 2.72 X ppmw desired
A-ft X 2.72 X ppmw desired
Total gal of liquid formulation required= ——
Ib ai per gal of i
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