APPLY PESTICIDES CORRECTLY
A GUIDE FOR COMMERCIAL APPLICATORS
RIGHT-OF-WAY
PEST CONTROL
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF PESTICIDE PROGRAMS
WASHINGTON, D.C. 20460
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Vegetation Management 2
Grasses 2
Broadleaf Plants 2
Woody Plants 2
Types of Herbicides 3
Selective Herbicides 3
Nonselective Herbicides 3
Plant Growth Regulators 4
Contact Herbicides 4
Translocated Herbicides 4
Factors Affecting Chemical Weed Control .. 5
Stages of Growth 5
Time of Year 7
Factors Affecting Foliage Application .... 8
Factors Affecting Soil-Applied Herbicides. . 9
Other Factors 10
Woody Plant Control 11
Drift 12
Herbicide Application Equipment 13
Managing Aquatic Plants 13
Recordkeeping 14
1976
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ACKNOWLEDGMENTS
PREFACE
This guide has been developed by Washington
State University under U.S. Environmental Protec-
tion Agency (EPA) contract number 68-01-2263.
This contract was issued by the Training Branch,
Operations Division, Office of Pesticide Programs,
EPA. The leader of this group effort was Dean G.
Swan, Washington State University. Editors were
Mary Ann Wamsley, EPA, and Donna M.
Vermeire, North Carolina State University.
Contributors were:
Robert L. Berger, Washington State Highway Com-
mission
William E. Currie, U.S. Environmental Protection
Agency, Washington, D.C.
Thomas M. Evans, E. I. DuPont DeNemours & Co.,
Dunwoody, Georgia
Lawrence E. Foote, Minnesota Department of High-
ways
Federal regulations establish general and specific
standards that you must meet before you can use or
supervise the use of 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 right-of-way weed control. Because the
guide was prepared to cover the entire nation, some
information 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:
• types of weeds,
• methods of weed control,
• safe and effective use of herbicides, and
• application equipment.
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INTRODUCTION
Rights-of-way are the areas involved in common
transport. Included are:
• Federal, State, county, and township highways
and roads,
public airports,
railroads,
electric utilities (including transformer stations
and substations),
pipelines (including pumping stations),
public surface drainage ways,
public irrigation waterways,
banks of public bargeways, and
bicycle, bridle, snowmobile, and other public
paths or trails (outside established recreational
areas).
Plant growth along the right-of-way must be con-
trolled to make sure that the right-of-way is:
• safe,
• usable,
• attractive,
• as inexpensive as possible to maintain, and
• not harmful to the environment of the surround-
ing area.
VEGETATION
MANAGEMENT
Consider what vegetation already exists along the
right-of-way and what may need to be added.
Usually grasses should predominate, but some le-
gumes may be desirable. For added beauty and
variety, encourage some wildflowers. Also consider
shrubs with colorful fruit and berries.
Plants along a right-of-way that can be considered
weeds are those which:
* are a safety hazard,
• are a nuisance,
• are unsightly,
• impede the use and maintenance of the right-of-
way,
• cause injury to man or animals,
• have been legally declared "noxious",
• crowd out desired plants,
• damage structures such as road surfaces and
rail ballast, or
• could harm adjacent crops if allowed to spread.
For weed control purposes, plants may be classed
as grasses, broadleafed, or woody plants.
GRASSES
Young grass seedlings have one leaf coming from
the seed. Grass leaves are generally narrow, upright,
and have parallel veins. Many grasses have fibrous
root systems.
GRASS
BROADLEAF PLANTS
Broadleaf plants have two seed leaves. They gen-
erally have broad, net-veined leaves and tap roots
or coarse root systems.
BROADLEAF
WOODY PLANTS
Woody plants are those that form wood. They
include:
• Brush and Shrubs—woody plants that have sev-
eral stems and are less than 10 feet tall. When
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trees are present, brush or shrubs may be called
understory.
CHEMICAL methods include:
• fertilization, and
• use of herbicides.
Trees—woody plants which usually have a single
stem (trunk) and are over 10 feet tall.
A plan for controlling plant growth along a right-
of-way may include both nonchemical and chemical
aspects. All the control methods must be coordi-
nated, since each has an effect on the others.
NONCHEMICAL aspects of the plan might include:
right-of-way location and design,
erosion prevention and cover establishment,
planting and encouraging desirable species,
utilizing competitive characteristics of desirable
plants,
mowing,
landscaping,
equipment allocation, and
controlled burning.
TYPES OF HERBICIDES
SELECTIVE HERBICIDES
Selective herbicides kill certain kinds of plants
but do not significantly injure others. Weeds must
be correctly identified, and the right chemical must
be correctly applied at the right time. Use spot
treatments wherever possible instead of broadcast
applications.
NONSELECTIVE HERBICIDES
Nonselective herbicides kill almost all plants in
the area of application. They may leave the soil
nonproductive (barren) for a year or more, depend-
ing on the chemical and the rate at which it is used.
Not all plants react the same way to any one
herbicide. Your choice of herbicide and application
rate depends on what plant you need to control.
Use nonselective herbicides in areas where bare
ground is needed. This type of control may be neces-
sary around substations, pole yards, pumping sta-
tions, storage areas, guardrails, signposts, runway
lights, parking areas, railroad yards, in railroad
ballast, in pavement cracks, and on highway
shoulders.
Plants in these areas could be a fire or safety hazard,
restrict sight, damage structures, provide a breeding
area for rodents and other pests, or reduce security.
The herbicide must be able to:
• kill existing exposed plants, and
• keep others from growing during the desired
period of time.
The application should be in a uniform pattern
at rates recommended on the label.
Wind, water, and soil erosion can cause herbi-
cides to move sideways after application and before
the chemical is fixed in the soil. Be careful to pre-
vent surface movement which could cause damage
to desirable plants in adjacent areas. Herbicides
seldom move off target when applied to ballast and
pavement cracks.
Nonselective herbicides usually should not be applied
to slopes greater than 6:1, horizontal to vertical,
without protecting the ground from erosion.
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The area can be protected by:
• covering it with asphalt or crushed stone, or
• mixing the herbicides with a cut-asphalt and
spraying it over the surface.
Nonselective soil-applied herbicides kill existing
perennial plants slowly. To improve their effective-
ness, combine them with contact and/or trans-
located herbicides. You can mow existing plants
closely and remove them before treating the area.
Remove plants from around guardrail posts with a
shovel. Blading with a grader can also be used.
Weed growth above
ground is eliminated.
Some weeds will not come
back. However, some
weeds may regrow from
roots. New weeds may
grow from seeds in the
soil.
PLANT GROWTH
REGULATORS
A vegetation cover is sometimes needed where
mowing is not practical. In some of these places,
you can use growth regulators to slow down plant
growth. They act only on the leaves they contact,
so they create no hazard from moving off target in
the soil. Because* they generally do not create bare
ground, they help prevent erosion. Use of these
chemicals may cause an increase in undesirable
plants, however, because not al! plants are equally
susceptible to them.
CONTACT HERBICIDES
These are herbicides that control weeds by direct
contact with plant parts. They must be applied to
the leaves. They are sometimes referred to as chem-
ical "mowers". Good coverage is necessary since
only the plant area contacted is controlled. Most
contact herbicides are nonselective.
TRANSLOCATED HERBICIDES
These herbicides move through the entire plant
system. They may build up in the plant's active
growth centers. Most of these herbicides are selec-
tive. Some of them are most effective when applied
to the plant foliage.
Spray growing vegetation
until wet.
Chemical translocates to
growing points and roots
Spraying of visible plant
foliage starts the action of
a contact herbicide. A
sprayer is usually used
to apply herbicide after
growth has started.
Herbicide is taken into the
plant (eaves where it inter-
feres with growth. The
plant begins to curl.
wither, and then turn
brown.
—and throughout the
plant.
Susceptible plant gradu-
ally dies.
Other translocated herbicides must be applied to
the soil. They are taken Into the plant through the
roots. These are called soil residual herbicides. The
length of time the soil remains relatively weedfree
depends upon the chemical used, amount applied,
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rainfall, soil type, and the plant species in the
treated area. Soil residual herbicides that are selec-
tive in some situations may be used nonselectively
by increasing the rate of application.
stage of growth than at any other stage. This is true
whether mechanical or chemical control is used.
Herbicides with foliar and/or soil activity are com-
monly used and usually effective at this stage.
Apply to soil and young
plants in early spring.
Rain washes herbicide into
the soil. It dissolves and
is absorbed by the plant.
SEEDLING IAN)
Herbicide is translocated
to growing points. Plant
yellows and gradually
dies.
Plants die and ground
may remain bare for a year
or more.
FACTORS AFFECTING
CHEMICAL WEED
CONTROL
STAGES OF GROWTH
Grasses and broadleaf weeds go through four stages
of growth:
• seedling,
* vegetative,
• bud and flowering, and
• maturity.
Seedling
The seedling stage of growth is the same for
annual, biennial, and perennial weeds. They are
all starting from seed. The weeds are small and
tender, so less energy is required for control at this
Vegetative (annuals)
During the vegetative stage of growth, energy
produced by the plant goes into the production of
stems, leaves, and roots. Control at this stage is still
possible but sometimes more difficult than at the
seedling stage of growth. Cultivation, mowing, and
postemergence herbicides are effective controls.
VEGETATIVE (ANNUALS)
GRASS
BROADLEAF
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Bud and Flowering (annuals)
When a plant changes from the vegetative to the
flowering stage of growth, most of its energy goes
into the production of seed. As plants reach this
more mature stage, they are usually much harder
to control by either mechanical or chemical
methods.
FLOWERING (ANNUALS)
!f
Maturity (annuals)
Maturity and seed set of annuals completes the
life cycle. Chemical control is usually not effective
at this stage since there is little or no movement
of materials in the plant. Once the seeds are ma-
ture, neither mechanical nor chemical controls can
harm them.
MATURITY (ANNUALS)
V
100,
PERCENT
CONTROL
90.
0
/E
ED
i
CONT
ROL
1
(ANNUALS)
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SEEDLING VEGETATIVE FLOWERING MATURE
STAGE WHEN HERBICIDE APPLIED
Biennials
Biennals, in two years, go through the same stages
as annuals. Control is usually easiest during the
seedling stage or when the weeds are still quite small.
Vegetative (perennials)
When the plant is small, part of the energy used
to produce stems and leaves comes from energy
stored in the underground roots and stems. As the
plant grows, more energy is produced in the plant
leaves. Some of this is moved to the underground
parts for growth and storage. Herbicides provide
some control at this stage.
VEGETATIVE (PERENNIALS)
(Degree of control at any stage will vary accord-
ing to the species of weed and the herbicide used.)
Bud and Flowering (perennials)
At this stage the plant's energy goes into the
production of flowers and seeds. Food storage in
the roots begins during these stages and continues
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through maturity. Chemical control is more effec-
tive at the bud stage (just before flowering).
FLOWERING (PERENNIALS)
WHO CONTKOl (MENENNUl*)
Maturity (perennials)
Only the above-ground portions of these plants
die each year. The underground roots and stems
remain alive through the winter and send up new
plant growth the next spring. Chemical control is
usually ineffective at this stage.
MATURITY (PERENNIALS)
(Degree of control at any stage will vary accord-
ing to the species of weed and the herbicide use.)
Woody Plants
Woody plants go through the same four growth
stages as other perennial plants. They do not die
back to the ground during the winter, but many
kinds lose their foliage. Woody plants can be con-
trolled with herbicides at any time, but control is
easiest when the plants are small. Foliar treatments
can be used at any time when the woody plants
have actively growing leaves. They usually work
best when the leaves are young.
TIME OF YEAR
With a fall application of an herbicide, the target
plant must survive three stresses:
* the effects of the herbicide,
• the effects of winter, and
• the heavy demand for nutrients caused by the
rapid growth period in the spring.
Fall treatments also may be safer for the environ-
ment, because many crops and other desirable
plants have completed their growth.
Perennial weeds that have regrown after being
controlled by chemical or mechanical methods
should be treated in the fall. At that time, herbi-
cides reach underground plant parts through the
natural translocation activity of the plant. Before
the first killing frost, nutrients move from the
above-ground parts of the plants to be stored over
winter in the underground parts. Underground parts
must be killed to control these weeds.
Winter annuals also can be more easily controlled
by a fall application of herbicide, because they are
seedlings at that time.
Spring treatments will control summer annuals
and perennials while they are in the seedling stage.
Fall and spring are ideal times to control biennials
in the rosette stage. In the fall, translocation is
occurring, and in the spring active growth begins
again.
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FACTORS AFFECTING
FOLIAGE APPLICATION
Location of Growth Points
GRASS—The growing point of a seedling grass is
protected below the soil surface. The plant will grow
back if the herbicide or cultivation does not reach
the growing point. Creeping perennial grasses have
buds below the soil surface.
SEEDLING ANNUM.
PERENNML
BROADLEAF—Seedling broadleaf weeds have an
exposed growing point at the top of the young plant.
They also have growing points in the leaf axils.
Herbicides and cultivation can reach these points
easily. The established perennial broadleaf plant is
hard to control because of the many buds oft the
creeping roots and stems.
BROADLEAF
SEEDLING ANNUAL
WOODY—Many woody plants, either cut or uncut,
will sprout from the base or roots.
Herbicide Entrance Into the Weed
LEAF SHAPE—Herbicide sprays tend to bounce or
run off of plants with narrow vertical leaves. Broad-
leaf plants tend to hold the spray. If recommended
on the label, add an adjuvant to increase spray re-
tention.
WAX AND CUTICLE—The herbicide must pene-
trate the leaf surface of the weeds. Thickness of wax
and cuticle affect the entrance of an herbicide into a
leaf. A leaf with a thin cuticle allows the spray solu-
tion good contact with the leaf surface. On a leaf
with a thick waxy surface, the spray solution tends
to stand up in droplets.
THICKNESS
AND WAX
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The wax and cuticle are thinner on young weeds.
This is another reason for applying herbicides at
the early growth stage.
HAIRS—Hairs on the leaf surface tend to keep the
spray solution from entering. The droplets stand up
on the hair and do not contact the leaf surface.
Seedling weeds usually have fewer and shorter hairs.
This is another reason for early control.
SPECIES—Species vary in growth habits and suscep-
tibility to herbicides.
ERECT
jj "^
PMMTIUTE NARROW
SIZE—Seedling weeds are easier to control than
established weeds. Smaller plants, regardless of their
stage of growth, are usually easier to control than
larger plants.
SEEDLING ESTABLISHED
FACTORS AFFECTING SOIL-
APPLIED HERBICIDES
Herbicide Characteristics
SOIL PARTICLE TIE-UP—One of the properties
of herbicides is magnetism. Some are not magnetic
at all; others have strong magnetism. Those without
a magnetic charge move down through the soil
quickly. Others, with positive magnetic charges,
tend to tie-up on the negative charge sites of soil
particles.
SOIL PARTICLE TIE-UP
f^f
;,CLAV - ^
/,
XLAY . O,
NON-MAGNETIC
MAGNETIC
LEACHING—Leaching is related to herbicide
characteristics and soil factors. Herbicides and soils
vary from nonleachable to completely teachable.
LEACHING
WATER
2.
PERSISTENCE—Persistence of an herbicide in the
soil depends on herbicide characteristics, rate of ap-
plication, soil texture, organic matter, precipitation,
temperature, and surface flow. Herbicides can:
• remain concentrated at the soil surface,
• partially leach (diluting effect), or
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• move through the soil in a front, allowing new
weeds to grow above.
Soil Type
Two factors affect the movement of herbicides that
are applied to the soil:
• the texture of the soil—how much sand, silt, and
clay the soil contains, and
• organic matter in the soil.
TEXTURE—Sand is coarse and does not have many
charge sites. The drawing shows a magnified sand
particle in the soil. The magnet-shaped particles are
herbicide molecules moving down through the soil.
The magnified circle shows the herbicide particle
moving past the sand surface. It does not tie-up.
TEXTURE
Silt has more sites than sand, but fewer than clay
and organic matter.
Clay is fine and has many charge sites. The draw-
ing shows a magnified clay particle. The positively
charged herbicide particle has fit into the negatively
charged slots on the clay particle. It is tied up and
will not continue moving through the soil.
TEXTURE
ORGANIC MATTER—Organic matter has many
more negative charge sites than even the finest soil
particles. The magnified circle in the illustration be-
low shows not only herbicide particles tied up on
the organic matter, but also particles of other ma-
terials such as water, sodium, calcium, and am-
monia.
ORGANIC MATTER
OTHER FACTORS
Soil Moisture
Soil-applied herbicides must be in moist soil to
be taken up by plant roots. This requires water in
the form of precipitation or irrigation.
Temperature
Temperature generally does not affect weed con-
trol results. It may, however, affect the amount of
time required for the herbicide to do its job. As
temperature increases, the herbicide may work more
quickly. In very cold weather, action of the herbicide
may be slowed.
Humidity
A foliar-applied herbicide will enter the leaf more
easily and rapidly at high humidity than at low
humidity. At high humidity, the leaf is more tender
and has a thinner layer of wax and cuticle.
Precipitation
If rainfall occurs soon after a foliar-applied herbi-
cide treatment, it may decrease effectiveness. Rain
increases soil moisture so soil-applied herbicides can
be more readily absorbed by the weeds. But too
much rain may move the herbicide too deep, past
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the zone where the weeds are. A hard rain may
move surface-applied herbicides out of the target
area. This is especially true if the soil surface is
packed or sloping.
Wind and Temperature
Wind and temperature can also affect the weed.
A hot, dry wind will cause:
• the openings on the plant surface to close,
• the leaf surface to become thicker, and
• the wax layer to harden.
These factors make it harder for herbicides to
penetrate the leaves.
WIND AND TEMPERATURE
BASAL SPRAYING
Herbicides are applied in oil to lower parts of
stems and exposed roots. It is best to fell large trees
and then treat the stumps.
CUT-SURFACE TREATMENT
The herbicide can be applied to the sapwood through
frill or notches. Another alternative is injection.
PLANT STOMATA CLOSE
LEAF SURFACE THICKENS
WAX LAYER HARDENS
WOODY PLANT CONTROL
Woody plants may be controlled mechanically or
chemically.
FOLIAR SPRAYING
Herbicides are applied to the foliage of woody
plants. Spraying woody plants at a young stage of
growth is best.
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STUMP TREATMENT
Close-cut stumps and exposed roots also may be
treated with herbicides in oil. It is best to treat im-
mediately after cutting. All sprouts must be treated.
SOIL TREATMENT
Applications are made to the soil around the base
of plants. Generally, granular herbicides are used.
These must be in moist soil for results to occur.
DRIFT
Be sure that the herbicides you use do not drift to
nontarget areas, either within the right-of-way or
outside of it.
There are two kinds of drift:
PARTICLE DRIFT—spray droplets which are car-
ried away from the application area by air move-
ment. The distance a particle of herbicide spray can
drift is determined by:
• the force of the wind,
• the distance from the spray nozzle to the ground,
and
• the size of the particle. The smallest particles,
such as those in fog or mist, present the greatest
drift hazard.
VAPORIZATION—evaporation of an active in-
gredient during or after application. The movement
of such vapor with wind currents may injure sensi-
tive vegetation. Vaporization is not as common as
particle drift, but it has more potential for moving
a greater distance.
To reduce the chances for drift:
• Use the lowest practical pressures.
• Leave an untreated edge.
• Angle nozzles toward the ground, slightly forward
in the direction of travel.
• Use nozzles with the largest practical openings.
• Use low-volatile formulations of the chemicals.
• Spray when wind speed is low.
• Do not spray during a temperature inversion
(when air is coolest at ground level, gets warmer
up to a certain height, and gets cooler from that
point on up).
• Spray when sensitive vegetation is not actively
growing.
DRIFT CONTROL AGENT
Special adjuvants and application systems have
been developed to help overcome some drift prob-
lems. Three of these are:
• foams (tank mixed, conventional formulation with
an additive),
• invert emulsions (three systems; mixed at nozzle,
mixed at pump, or tank mixed), and
WATER
(CONTINUOUS
PHASE)
WATER
OIL
CONVENTIONAL
EMULSION
INVERT
EMULSION
spray additive stabilizers (thickeners in dry form
mixed with conventional formulation in tank with
agitation).
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Though they differ in method, all three have sim-
ilar advantages:
• better control of both particle drift and vaporiza-
tion, and
• more highly visible spray, which allows you to
see where you are placing it.
HERBICIDE APPLICATION
EQUIPMENT
The equipment used is of two general types;
• airborne equipment, carried either by fixed wing
aircraft or by helicopter, and
• ground equipment (including floating equipment
on drainage ways, irrigation waterways, and barge-
ways).
Both airborne and ground equipment are available
for applying:
• conventional sprays (water, oil in water, and oil
in oil),
• invert emulsions, and
• granular formulations.
Rights-of-way have many obstacles which make
the use of conventional spray booms difficult or im-
possible. The "manifold" sprayer (usually six nozzles
with individual on-off valves, each set for different
distances but with adjacent swath patterns) and the
"handgun" sprayer nozzle are widely used. You also
can get special equipment for applying herbicides to
rights-of-way from aircraft.
Much special equipment has been developed for
specific right-of-way jobs. It includes equipment for
mounting on trucks, trailers, barges, rail vehicles,
and all-terrain vehicles. The lack of a full range of
well-adapted, readily available equipment for right-
of-way spraying is a problem. Another difficulty in
right-of-way application is the maintenance of a
supply base. Because most rights-of-way are long
and narrow, the operation continually moves away
from its supply base. Return travel time is often
excessive. Low application rates with minimum
amounts of water or oil carrier make the job faster
and more efficient since it reduces the supply runs.
Mobile supply units are often needed. One unit,
spray and supply combined, may be more efficient.
MANAGING AQUATIC
PLANTS
Aquatic weeds are plants which interfere with the
use or performance of water areas. They may:
• make the area less attractive,
• interfere with recreation,
• obstruct the flow of water in ditches or canals,
and
• harbor insects or rodents.
The first step in control is to identify the general
problem. Then you must identify the specific species
to be controlled. Cooperative Extension Service per-
sonnel, written material, and herbicide manufac-
turers' representatives can help you.
The basic approaches to aquatic weed control are:
• design and construction of the water area,
• operation and maintenance,
• mechanical control, and
• chemical control.
The best control method is that which gives safe,
effective weed control while causing the least harm
to other parts of the environment.
CHEMICAL CONTROL
The use of herbicides to control weeds in water
areas is often very effective. Use the herbicides as
the label directs.
As you analyze any aquatic weed problem, con-
sider the following:
BIOLOGICAL ASPECTS:
• Identify the problem species.
• Identify other species present.
• Determine the density and stage of growth of the
weeds, and how much area they cover.
• Determine what species of fish are present.
WATER USE ASPECTS:
• Know the uses of the water in the treatment area.
• Find out how long the water can be quarantined
from each use.
• Know how much water leaves the treatment area
and what it will be used for.
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PHYSICAL ASPECTS:
* Determine the size of the area to be treated.
• Determine the depth and movement of the water.
* Note the clarity of the water.
• Determine the water temperature.
• Determine the water quality.
RECORDKEEPING
Keep detailed records of control measures so that
evaluations can be made of previous activity in order
to improve future control and to be able to have
accurate information in case of outside liability
actions.
Such records may include:
• areas treated and date,
• material and rate applied,
• environmental conditions,
• equipment and crew,
• evaluation of effectiveness,
• problems encountered, and
• damage claims.
* U.S. BOYHNMfHT PSWTlNQ OfFICt 1976- 210-810/160
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