Agriculture Handbook No. 269

1

Ag8UAk

No.269

Herbicide

Manual

For

Noncropland

Weeds

AGRICULTURAL RESEARCH SERVICE, U.S. DEPARTMÉ^^T OF AGRICULTURE

in cooperation witb

BUREAU OF YARDS AND DOCKS, DEPARTMENT OF THE NAVY
Agriculture Handbook No. 269

For

Noncropland

Weeds

By R. S. Dunham

AGRICULTURAL RESEARCH SERVICE, U.S. DEPARTMENT OF AGRICULTURE

in cooperation with

BUREAU OF YARDS AND DOCKS, DEPARTMENT OF THE NAVY

Washington, D.C Issued March 1965

For sale by the Superintendent of Documents, U.S. Government Printing OflSce

Washington, D.C. 20402 Price 50 cents
ACKNOWLEDGMENT

In the preparation of this handbook, more than a thousand publications, including reports, bulletins, journal articles, chemical company literature, and a few

books, were reviewed and abstracted. The author is indebted to some 700 investigators whose research findings have been the main source of material. To all of

these and to die many who wrote personal letters, he wishes to express his appreciation; and also to the members of the military technical advisory group. Department

of Defense, for their constructive assistance.
Some chemicals used for weed control can be injurious to man if handled carelessly. They can also be

injurious to desirable plants, livestock, wildlife, and fish if improperly applied. Care should be exercised in the use of herbicides and

the disposal of unused herbicides to

avoid polluting streams and water

supplies. Precautions for handling

and applying that are printed on the

container label should be followed.

In this handbook general precautions for the use of herbicides are

given in the section on "Hazards of

Handling and Application." In the

section on "Current Herbicides" dangers associated with the handling

and application of specific herbicides

are indicated by Roman numerals

that refer to precautions given in the

section on "Hazards of Handling

and Application." Precautions for

herbicides that require special warnings are given under "Application

of Herbicides."

Use of product names in this handboc^ does not

constitute a guarantee or warranty of the products

named and does not signify that these products are

approved to the exclusion of comparable products.
CONTENTS

Page

How to use this handbook 1

General information 2

Growth habits and reproduction of weeds 2

Classiûcation of herbicides 2

Hazards of handling and application 3

Herbicide labels 6

Current herbicides: chemical, physical, and biological

properties and adaptation 6

Acrolein 6

Amitrole 6

Amitrole-T 7

Ammonium sulfamate 7

Arsenicals 7

Benzole acid compoimds 8

Chemical combinations 9

Copper sulfate 9

2,355,6-tetrachloroterephthalic acid 9

Dalapon 10

Dichlone 10

0-(2,4-dichlorophenyl)-0-methyl isopropylphosphoramidothioate 10

Dinitro compounds 10

Diquat 11

Endothall 11

Fenac 11

Fumigants 11

Hydrocarbons, including chlorinated hydrocarbons 12

Maleic hydrazide 13

Mixtures 14

Octachlorocydohexenone 15

Pentachlorophenol 15

Page

Phenoxy compounds 15

Phenylurea compounds 18

Phenylmercuric acetate 19

Sodium chlorate 19

Triazines 19

Trichloroacetic acid 19

Herbicides and mixing of spray materials 20

Formulations of herbicides 20

Purchase of herbicides 21

Mixing of spray materials 22

Storage of herbicides 24

Application equipment 24

Description 25

Requirements for diflferent types of sprays 28

Operation 29

Cleaning and preparation for storage 31

Application of herbicides 32

All vegetation 33

Weeds in specific areas 39

Woody plants 40

Weeds in woody plantings 47

Poison-ivy, poison-oak, and poison-sumac 47

Turf weeds 48

Aquatic weeds 52

Weed species and herbicides for control 57

Appendix 83

List of equivalents 83

Glossary 84

Herbicide index 87

General index 89

V
Herbicide Manual

for Noncropland Weeds

By K. S. DUNHAM, research agronomist, Crops Research Division,

Agricultural Research Service

HOW TO USE THIS HANDBOOK

Oeneral Information,—This introductory material on growth habits and reproduction of weeds;

use, mode of action, and hazards of herbicides;

and herbicide labels applies to all phases of weed

control and will be helpful in understanding what

follows. ^ There is also introductory material for

each section of the handbook and for divisions of

each section.

Current Herhicides,—In this section herbicides

currently available (1963) are listed and described. They are arranged alphabetically by accepted common names; by chemical names, when

no common name is available ; or by groups, when

two or more related herbicides are described together. The description includes the chemical,

physical, and biological properties and the adaptation of the herbicide to aid the operator in making choice of a chemical best suited to his situation. A list of weeds known to be resistant to the

chemical is given if this information is available.

These weeds are considered so difficult to kill with

the herbicide that its use for their control is not

recommended.

Herbicides a/nd Mixmg of Spray Materials.—

This section describes formulations of herbicides

and gives directions for mixing with carriers and

diluents. It discusses the bases for comparison

of various commercial preparations of a herbicide and lists the requirements for good storage.

The topics are indexed in the "General Index."

Application Equipment.—^This section discusses

kinds of application equipment: its parts, such

as pumps and nozzles; its calibration; its operation; and its care. Topics are indexed in the

"Greneral Index."

Application of Herbicides.—In this section two

kinds of weed problems are discussed: (a) weed

sites, such as storage areas, ditchbanks, roadsides,

and railroads; and (b) weed groups, such as

woody weeds, turf weeds, and aquatic weeds.

Where bare ground is the objective, discussion can

be found under complete vegetation control and

soil sterilants. Directions for using the herbicides instead of descriptions are given. Weed

sites and weed groups are listed in the "General

Index" ; individual species of weeds together with

the herbicides to which they are susceptible, intermediate, or resistant are listed in "Weed Species

and Herbicides for Control" (table 5) ; and herbicides are listed in the "Herbicide Index."

Weed Species and Herbicides for Control.—

In this section the response of weeds to herbicides

is tabulated. The species mentioned in the text

are listed alphabetically by common names. The

botanical name is given for identification. Each

species is classified as annual (A), aquatic (Aq),

biennial (B), perennial (P), or woody (W). Eesponse to applications of herbicides is indicated

by S for susceptible, I for intermediate, and K

for resistant.

Herbicide Index (pp. 87 and 88).—This index

includes the names of all herbicides included in

the handbook. They are listed alphabetically by

common names or designations. Chemical names

are also given for identification. Discussions referred to by page numbers comprise chemical,

physical, and biological properties, and adaptation, and application.

General Index (pp. 89 and 90).—This index lists

references of a general nature that are not included in table 5 or the "Herbicide Index."
AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

GENERAL INFORMATION

Chemical control of weeds is not an exact science. Results cannot be predicted with the same

accuracy as is expected in the physical sciences.

Nevertheless, a knowledge and especially an appreciation of the factors that influence results in

the use of herbicides are essential to the best

control.

GROWTH HABITS AND REPRODUCTION OF WEEDS

Annuals are plants that mature in one season.

They are propagated by seed. Foxtail, crabgrass,

common ragweed, wildbuckwheat, and several

mustards are examples. A variation of the true

annual is the winter annual, which germinates in

the fall, lives over winter, and matures early the

next season. Some plants of pennycress, common

chickweed, corncockle, shepherds-purse, and yellow-rocket behave as winter annuals. The capacity of individual plants to produce thousands or,

in some instances, hundreds of thousands of seeds

that may shatter to the ground provides an enormous source of new plants the following season.

Many of these seeds remain viable for years when

they are buried in the soil. The prolific production of seed, the buildup of weed-seed populations

in the soil, and the length of time seeds remain

viable in the soil are nature's way of insuring that

annual weeds will be perpetuated. It is these

properties of annual weeds that make eradication

almost impossible. If the topgrowth is killed before seed is produced, the life cycle of that plant

is ended, since it cannot recover. However, the

reservoir of seeds in the soil may produce new

plants for many years.

Biennials require two seasons to complete the

reproduction cycle. Their growth period is longer

than that of winter annuals. Since they are

propagated by seed only, seedlings can be treated

as the seedlings of annuals. Burdock, eveningprimrose, common mullein, and yellow goatsbeard

are biennials.

Perennials are plants that live more than 2

years. Many have additional means of perpetuation; they are provided with storage organs in

the form of stolons (prostrate stems), rhizomes

(underground stems), bulbs, crowns, and roots.

Supplies of food are laid up in these organs by

the plant to feed a new growth the next year.

The new shoot comes from a bud and lives on

stored food until it becomes established. Unlike

the annual plant, the topgrowth of a perennial

may be killed and still the plant can live and

propagate itself because of its storage organs. To

control this vegetative reproduction, the food reserves must be materially reduced or the storage

organs destroyed. The food stored by the plant

is ÜIQ excess manufactured by the green leaves

and stems over and above what is necessary for

growth; therefore, if photosynthesis can be prevented, the buildup of reserves will be curbed.

For control of perennials, the new growth is allowed to draw on food reserves until it becomes

sufficiently established to manufacture its own

food and then the topgrowth is killed. Quackgrass, Canada thistle, johnsongrass, buttercup,

and nutgrass are perennials.

CLASSIFICATION OF HERBICIDES

Herbicides are grouped, on the basis of use, into

sélectives and nonselectives and, on the basis of

mode of action, into contact, translocated, and

sterilant chemicals.

Selective and Nonselective Chemicals

Selective herbicides are those that kill certain

weed species without seriously injuring the desirable plants among which they are growing. Those

that kill crabgrass or dandelions in a grass sod

are examples. The reasons for selectivity in some

combinations of weeds and desirable plants are

known; in other situations, they are unknown.

Crabgrass can be killed in bluegrass sod because

it is an annual growing among perennial plants

that can recover from spray injury. Why dandelions can be killed in bluegrass sod is not fully

known ; certain herbicides kill broad-leaved weeds

and not grasses and vice versa.

Nonselectives kill vegetation with little discrimination. Certain species, however, are resistant and some escape. E-esistant species are physiologically resistant to the chemical; some escapes

are perennials that have part of their root system

below treated layers of soil; others are annuals

and shallow-rooted perennials that reinfest an

area after the chemical has leached below the surface layer.

Contact, Translocated, and Soil-Sterilant

Chemicals

Contact herbicides kill the tissues that are

wetted with the spray. Whether the plant dies

or recovers depends on whether it has a protected

growing point. Perennials usually have underground buds that will regrow.

Translocated chemicals are absorbed by the

leaves and stems or by the roots and move

through the vascular system to leaves, buds, and

root tips. When absorbed by the leaves and

stems, the chemical is commonly moved with the

food materials that were manufactured in the

leaves and stems. When absorbed by the roots,

it moves in the water-conducting tissue. The
HERBICIDE MANUAL

growth-regulator type of translocated herbicide

IS a synthetic compound that behaves like a plant

hormone. It accumulates mostly in areas of rapidly dividing cells, upsetting the normal metabolism of the plant and causing death of the cells.

Foliar applications of translocated herbicides are

of great practical value, because small amounts

are effective and thejr can be applied in small

volumes of water or oil.

A soil-sterilant herbicide makes a soil incapable

of supporting higher plant life, but it does not

necessarily kill all life in the soil, such as fungi,

bacteria, and other micro-organisms. Its toxic

effects may remain for only a short time or for

years. Kesidual toxicity depends on: (1) the

chemical and its rate of decomposition or leaching, (2) the colloidal and chemical content of the

soil, (3) species tolerance, and (4) rate of application.

(1) Herbicides vary in their rate of disappearance from the soil because of volatility, susceptibility to decomposition by soil micro-organisms,

and solubility. For example, some of the carbamates are volatile at high temperatures and rapidly lose their toxic effect during the summer

months. Certain soil micro-organisms effectively

decompose 2,4-D. Amitrole is soluble in water

and readily leached.

(2) Some herbicides are readily adsorbed by

mineral and organic colloids and rendered unavailable or made slowly available for plant absorption. The fertility and pH of a soil are also

influencing factors in the persistence or availability of toxic amounts of certain chemicals.

For example, monuron and diuron are adsorbed

on clay colloid particles so that leaching is difficult. Sodium chlorate is more easily absorbed by

plants growing in soil low in nitrates.

(3) Plant species vary widely in tolerance to

soil sterilants. Plants resistant to each herbicide

are listed in section on '^Current Herbicides," and

hard-to-kill species are designated for each herbicide under "Application of Herbicides."

(4) Heavy rates of application generally last

longer than light rates.

HAZARDS OF HANDLING AND APPLICATION

Nearly all herbicides are potentially dangerous

in one way or another, but they are not likely to

cause injury if used properly and if recommended

precautions are observed. The dangers associated

with the handling and application of these chemicals are of several kinds and possible injury is

not limited to the operator. Any or all of the

following may be affected: Operator and handler, livestock, desirable plants, equipment, and

game and fish.

The following general discussions apply to

classes of herbicides rather than individual chemicals. More specific information is given in sections on "Current Herbicides" and "Application

of Herbicides." In addition:

Kead the label on each container before using

the contents. Follow instructions; heed all

cautions and warnings. Store in original

labeled containers. Dispose of empty containers by burying them at least 18 inches

deep in an isolated area away from water

supplies.

I. Operator and Handler

The person who mixes and applies the spray

or spreads the dry product could be poisoned

from swallowing the herbicide, from skin absorption, or from inhalation. In each case, there is

greater danger from the concentrated material

than from the diluted spray solution or suspension.

(a) If the concentrate or spray is swallowed,

induce vomiting immediately- Dissolve a tablespoon of salt in a glass of warm water and administer repeatedly until the vomit fluid is clear.

If salt is not available, tickle the throat by inserting a finger. Have the victim lie down and

keep quiet. Call a physician.

The toxicity of herbicides varies widely. The

relative degree of toxicity is indicated in table 1.

The ratings describe the acute (not chronic)

lethality of each herbicide when swallowed by

laboratory animals. Usually toxicity in the field

is less, because seldom is such a dose swallowed

or absorbed and diluted sprays are handled more

often than concentrates. Nevertheless, neither

chemical concentrates nor dilute sprays should

be kept in unlabeled containers, especially not in

containers commonly used for potable liquids.

Unfortunately humans do not always react like

small animals. It is always possible that a human will stand a correspondingly larger dose of

a given chemical than results with animals would

indicate or vice versa. There is no way to determine accurately whether a lethal dose tor man is

larger or smaller than the LD50 (lethal dose for

50 percent of animals tested) for a laboratory

animal. But animal studies are the best guide

available.

(b) Absorption by the skin and irritation of

skin and eyes can largely be prevented. Keep

exposure to a minimum until skin reaction to a

new chemical is learned. Some individuals are

hypersensitive to certain chemicals and have allergic reactions that are impossible to predict

without skin tests. For most herbicides, washing

hands and face with soap and water after handling is sufficient protection. Prolonged contact

is more dangerous than short exposures. For the

more readily absorbed chemicals and those that

are irritating, wear clean clothing that covers the
AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Relatwe acute toxicities of herbicides fed wnd dermal response

when applied to laboratory animals

Herbicide Acute oral toxicity

Dermal

response

rating*

Chemical tested

Approved

common

name!

Chemical

WSA

designation 2

Rating 3

Test

animal

Active

ingredient

Commercial formulation

Acrolein— 1

3

4

3

2

1-2

2-3

1

3

3

3

2

4

3-4

4

2-3

2-3

2

4

3

3

3

2

3

4

3

1

3

3

1-2

3

3

4

4

2

1-2

3

4

2

3

3

3

2

3

2

1

3

4

4

2

3

3

3

3

- Rats X

Amine methylarsonate (AMA)_ _ do

__ do -

do

3

2

1

3

2

2

4 and 5

1

2

2

2

2

2

2

5

X

X

Ammonium sulfamate - AMS X

Aromatic solvents - X

Arsenate, calcium» Rats

do

do

do

do

do

X

Arsenate, lead - X

Arsenite. sodium« _ X

A •f-TQ^'irip X

Borate-monuron BMM _ .

BDM

X

Borate-2,4-D X

Carbon disulfide X

Chlorate-borate CBM

CBMM

Rats

do

do

do

Rabbits

X

Chlorate-borate-monuron X

Chlorate-chloride X

fJhlordane X

Chloropicrin - - X

Copper sulfate- Rats

do

do

do

do _

do_-

do

do

do

do

do

do

do

- do

- do

_ do

do ^^-

- do _

X

DfllaDon 2

2

_-

__

2

2

5

1

2

3

3

1

2

3

X

Dalapon-silvex X

Dii*flmba

Dichlone X

Dimiflt

2,4-dichlorophenoxyacetic acid

0- (2,4-dichlorophenyl) -O-methyl

isopropylphosphoramidothioate.

3,5-dimethyltetrahydro-l,3,5,2Hthiadiazine-2-thione.

Dinitros - -

Disodium monomethylarsonate .

2,4-D —

DMPA

DMTT

DNAP,

DNBP,

DNO.

DMA

X

X.

X

X

X

X

X

Dluron

EndothalL

Erbon - - X

Fenac X

TT'ATm'TfiTi X

Fenuron- X

TCA.

"~

Gasoline _ - nr

Kerosene Rabbits X

Maleic hydrazide diethanol

amine.

Maleic hydrazide sodium salt

Methyl bromide

MH

MH__

Rats _ -

do 3^

5

2

2

2-methyl-4-chlorophenoxyacetic

acid.

M.ÜPÁ Rats

_ do

- do

Mice

X

Monnron _ X

X

X

MonuronTCA

Octachlorocyclohexenone

Oil, petroleum _

OCH- -

——

5

5

4

2

1

2

3

1

4

1

2

X

Pentachlorophenol POP - - . Rats X

Mammals—

Rats . — do -

do

- do

do

do_ __

do- -

Phenylmercuric acetate PMA X

Silvex- X

Simazine X

X

X

X

Sodium chlorate

Sodium-N-methyldithiocarbamate.

2,3,5,6-tetrachloroterephthalic

acid.

Trichloroacetic acid

SMDC

DCPA

TOA

2,3,6-TBA_.

2,4,5-T

——

X

2,3,6-trichlorobenzoic acid

2,4,5-trichlorophenoxyacetic acid-

]f

y

See footnotes on p. 5.
HERBICIDE MANUAL

body. Kemove clothing after it has become contaminated with the chemical. Use synthetic rubber gloves. Where splashing may occur, wear

gog^es. If the spray or dust is spilled on the

skin, wash thoroughly with soap and water; if in

the eyes, wash with plain water and see a doctor.

Liquid concentrates and powders should be put

into containers that can readily be lifted by the

operator in the field. Packages of powders should

be small enough so that it is unnecessary to remove the contents with a scoop.

(c) Inhaling vapors, dusts, and spray mists

can also be avoided. Use a mask when label directions indicate the need. In the case of a severe

exposure, move the patient into fresh air, administer artificial respiration if needed, and call a

physician.

(d) Some chemicals are fiammable or support

fire. Avoid ignition from friction, sparks, and

contact with combustible materials.

(e) Some are dyes that color skin and hair if

not protected.

II. Livestock

The chief dangers of poisoning livestock are

from consumption of herbicide remnants in open

containers and of contaminated water.

2,4-D and similar compounds may increase the

palatability of plants not ordinarily eaten. If

these are poisonous species, sickness and death

may result. The nitrate content of some plants

may be increased when sprayed with 2,4-D. Tliis

nitrate is reduced to nitrite by micro-organisms

in the intestinal tract of herbivorous animals.

Because nitrite in the bloodstream interferes with

the effective transport and use of oxygen, the animal suffocates. However, increased nitrate content of plants does not always follow spraying.

Furthermore, some natural conditions also produce high nitrate, so that many weeds contain

enough to cause poisoning whether sprayed or not.

III. Desirable Plants

Certain precautions are necessary to prevent

damage to adjacent valuable plants. This damage

may result from drift, washing, or leaching.

(a) Drift hazards are greatest when herbicides

that affect the leaves of plants are used. These

may be of the growth-regulating type, such as

2,4:-D, 2,4,5-T, and silvex, or of the contact type,

such as PCP, the petroleum oils, and dinitros.

Danger is least when dry applications are made

of nonvolatile herbicides. Drift occurs not only

with volatile herbicides, such as the high-volatile

esters of 2,4-D and 2,4,5-T, but also from a spray

that has been atomized into a mist by high pressure and small nozzle opening whether the formulation is volatile or not. The control of drift is

discussed on pages 30 and 46.

(b) Washing is an important hazard on slopes,

bare ground, and pavements. The herbicide may

be carried by surface runoff to valuable plants

downslope. Do not drain or flush equipment

where runoff to desirable plants may occur.

(c) Leaching moves chemicals downward

through the soil. If they are readily absorbed by

roots, plants whose roots extend under the treated

area are likely to be injured. Avoid treating

such areas with soil sterilants. Do not drain or

flush equipment where leaching to the roots of

desirable plants may occur.

IV. Equipment

Some chemicals corrode the metal parts of

spraying equipment; oils and solvents injure rubber. Thorough draining and cleaning of equipment with water and a detergent is sufficient protection against most chemicals. When corrosive

chemicals are used, coat the metal parts of the

equipment with protective paint, oil, or undercoating after use or purchase equipment with noncorrosive metals. Neoprene rubber is resistant to

oils and solvents.

1 Approved by the American Standards Association as an American Standard common name except chlordane,

which was approved as a common name by the International Committee on Common Names for Pesticides.

2 Accepted for use in Weed Society of America publications.

* Numerical rating is based on the following classification of the Federal Insecticide, Fungicide, and Rodenticide

Act.

Bating Class LDgoj mg./hg. Lethal dose for 150-pound man

1 Highly toxic 50 and below Few drops to 1 teaspoon

2 Moderately toxic above 50 to 500 1 teaspoon to 1 ounce

3 Toxic above 500 to 5,000 1 ounce to 1 pint or 1 pound

4 Nontoxic above 5,000 1 pint to over 1 quart

"Lethal dose for 150-pound man" is based on table in Clinical Toxicology of Commercial Products by Gleason, M.

N., Gosselin, R. B., and Hodge, H. C, Williams and Wilkins Co., Baltimore, Md. 1957.

•* Numerical rating is based on the following classification : 1, nonirritating ; 2, mildly irritating ; 3, moderately

Irritating; 4, causes burns and blisters; 5, absorbed and poisonous.
AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

V. Game and Fish

Most herbicides are less dangerous than insecticides to wildlife. There are a few, however, such

as the arsenicals and dinitros, that can poison

animals. Most injury results from overdoses and

spillage. Promiscuous spraying and spraying

that results in vegetation of similar species can

destroy cover, but herbicides can also be useful

in management. Openings in wooded areas, such

as the clearing for utility company rights-of-way

and spraying of hardwoods in stands of pine can

be beneficial to wildlife.

A few herbicides are very toxic to fish, but

many can be used safely for the control of aquatic

weeds. The control of submerged weeds in ponds

or streams can be beneficial to fish populations.

Safe amounts of herbicides, expressed in parts of

the chemical per million parts of water, vary

widely with age, size, and species of fish.

Whenever a proposed spraying program might

endanger game and fish, consult Federal or State

Fish and Wildlife Service for advice.

HERBICIDE LABELS

Labels on the herbicide container are written

with great care to state only facts. Recommendations on labels for materials sold interstate must

be registered with the U.S. Department of Agriculture before the label can be authorized. The

label should always be read by the operator. It

tells, first, what the herbicide is. For instance,

2,4-1) is sold as a sodium or amine salt or a volatile or low-volatile ester. Eecommendations differ

for various herbicides and for various formulations of the same basic chemical.

The label tells the amount of acid equivalent,

phenol equivalent, or active ingredient in the

product. This information permits a comparison

of concentrations in various formulations, a comparison that is useful for figuring amounts to apply and for contrasting prices. The label also

makes recommendations for use and gives rates

and time of application. Certain warnings are

stated when necessary to protect the operator

from poison or irritation by the chemical and to

protect susceptible plants from injury.

To Control Weeds With Chemicals

1. Identify the weeds you want to control.

If in doubt, obtain assistance from a

weed specialist or other authoritative

source.

2. Select the right herbicide to control

these weeds without harm to desirable

plants nearby.

3. Mix the chemical according to mixing

directions. Do not use more than recommended amounts.

4. Eemember that weather conditions, the

soil, and the growth stage of the weeds

affect the action of many herbicides.

So, follow directions on when and how

to apply the materials.

CURRENT HERBICIDES: CHEMICAL, PHYSICAL, AND

BIOLOGICAL PROPERTIES AND ADAPTATION

The dangers associated with the handling and

application of certain herbicides are discussed on

pages 3 to 6. Roman numerals in parentheses

after the herbicide names in this section indicate

the section in that discussion that applies to the

chemical described. The small letters indicate the

paragraph within the section.

ACROLEIN (ACRYLALDEHYDE) (I, II, V)

Acrolein is a highly reactive solution that controls submersed aquatic weeds in irrigation and

drainage channels. It is extremely toxic to mammals, to fish, and to other aquatic animal life. It

is highly volatile and flammable, and its vapor is

a powerful irritant to the eyes and respiratory

passages. Because of these properties, the chemical must be metered or pumped from the closed

container into the water of the channel without

contact with air. A formulation of acrolein is

available for treatment of irrigation and drainage canals by licensed operators with especially

adapted equipment.

AMITROLE (3-AMIN0-1,2,4-TRIA20LE) (III, A)

Amitrole is formulated as a water-soluble powder for applying in solution. The commercial

product is sold in two concentrations : 50 percent

and 90 percent amino triazole. It is not hazardous to handle, is not acutely toxic to mammals,

and, at normal rates of application, is not harmful to fish.

Amitrole can be used for the control of herbaceous weeds, woody plants, and aquatic weeds

either alone or in combination with other herbicides. It is safer than 2,4-D, 2,4,5-T, or silvex

where drift would be injurious to nearby plants.

Resistant weeds are: alligatorweed; bindweed,

field; caraway; cherry; chinquapin, golden; cot-
HERBICIDE MANUAL

tonwood; dandelion; dogwood; elderberry; elm;

fir, balsam; garlic, wild; greenbrier; gum, black;

hackberry ; hawthorn ; hazel; Indian hemp; johnsongrass; kikuyugrass; knapweed, Russian; larkspur, tall; maidencane; maple; mesquite, honey;

mulberry ; nimblewill ; nutgrass, purple ; oak, red,

shinnery, Turkey, and white; onion, wild; pine,

white; plum, chickasaw; redcedar, eastern; sassafras; shadbush; smartweed, swamp; smilax;

snowbrush ; sorrel, red ; spicebush ; spruce, black ;

toadflax, yellow; trumpetcreeper ; tuliptree;

white-cedar; whitethorn, mountain; wiklbuckwheat; willow; and yucca {Y. smalliana).

Amitrole is effective against such herbaceous

weeds as horsenettle ; thistle, Canada ; and whitetop. Alone, it is adapted for land where long

residuals are not required, where quick topkills

are needed, and where spot treatment of weeds

that have survived or escaped treatment with a

soil sterilant is desirable.

Combined with residual-type herbicides, it

makes a mixture that not only quickly kills plant

growth above ground but also prevents weed

growth for one or more seasons and acts more

effectively than amitrole alone against deep-rooted

perennial weeds. A mixture with dalapon often

increases effectiveness against grasses. In combination with simazine, monuron, diuron, or dalapon it can be used in storage yards and parking

lots, on railroad beds and ballast, under pipelines,

under guide rails and surrounding signposts on

highways, on public utility rights-of-way, around

buildings and tank farms, along ditchbanks and

fence rows, around radio antenna installations

and airstrip runway lights, on crushed-rock blankets, and in similar areas where any plant growth

is undesirable.

Amitrole is too specific to be a general brush

killer. It is especially effective on ash, white;

locust, black; poison-ivy; poison-oak; poisonsumac ; and sumac, staghorn. It has been promising on some conifers. It is readily translocated,

so it can be applied to the leaves; but it is not

absorbed through the bark, so it can be used to

kill vine growth on trees without injury.

Amitrole is more expensive than 2,4-1) for the

control of cattails and bulrushes, but it is safer

to use near crops sensitive to 2,4-D.

AMITROLE-T (3-AMIN0-1,2,4-TRIA20LEAMMONIUM THIOCYANATE)

This is a liquid formulation containing 2

pounds of 3-amino-l,2,4-triazole per gallon. The

ammonium thiocyanate increases the sensitivity

of grasses to amino triazole so that effective control results from lower rates than from amitrole

alone. Itis more effective than amitrole on quackgrass, Eeed canarygrass, and water-hyacinth.

Resistant weeds are: bindweed, field; johnsongrass; knapweed, Russian; spurge, leafy; and

thistle, Canada.

AMMONIUM SULFAMATE (IV)

Ammonium sulfamate, designated as AMS by

WSA, is a granular material that is very soluble

in water and that breaks down rapidly in moist

soil. It is nonflammable, nonvolatile, and strongly

toxic to plants. No special handling precautions

are necessary. It is sold in a formulation containing 95 percent ammonium sulfamate in a

crystal form and as a solution containing 5.3

pounds of 95 percent ammonium sulfamate per

gallon.

Ammonium sulfamate is commonly substituted

for the phenoxy compounds in areas where crops

sensitive to these chemicals are grown. It is a

contact, nonselective herbicide effective over a

wide range of conditions and species. It is especially effective on poison-ivy, poison-oak, and

poison-sumac. Ammonium sulfamate, in the crystal form or in concentrated solutions, is successfully used for stump applications. It is corrosive

to metals, especially brass and copper. Stainless

steel, aluminum, and bronze are resistant. Spray

equipment must be protected, but corrosion of

fences, guy wires, and telephone wires is negligible.

It is not effective against eastern redcedar,

snowbrush, and Turkey oak.

ARSENICALS (I, II)

The arsenicals are among the cheapest herbicides, but they must be handled carefully.

Two groups of arsenicals are used for killing

weeds : the inorganic and the organic.

Inorganic Arsenicals

The inorganic arsenicals include sodium arsenite, lead arsenate, and calcium arsenate. They are

all highly poisonous to man and animals if swallowed. Their effectiveness for weed control depends on their arsenic content, which is commonly

expressed in percent of arsenic trioxide (AS2O3).

Sodium arsenite

Sodium arsenite is readily soluble in water. It

is formulated as a dry powder or in stock solutions in concentrations up to 9.5 pounds AS2O3

per gallon. Sodium arsenite is commonly the

active ingredient of commercial arsenic preparations. Under conditions of light and intermittent

rains, treated soil may remain sterile for 4 years.

If steady rains or flooding follow treatment, additional applications are necessary to maintain

bare ground. The sodium arsenite sprays or dried

residues on vegetation are salty and may attract

animals.
8 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

Sodium arsenite is best adapted for annual species and shallow-rooted perennials. Soil texture

is the principal factor affecting its use. It is most

effective in light, sandy soils and least effective

in heavy calcareous clay soils, since arsenic is

strongly adsorbed by soil colloids.

E-esistant upland species are: bedstraw, cleavers; bracken; fiddleneck, coast; knotweed, prostrate ; orache ; paspalum ; thistle, Canada ; and

Turks-rug. Eesistant aquatics are: star-thistle,

yellow; stonewort; waterlily; and watershield.

Lead arsenate and calcium arsenate

Both compounds are practically insoluble in

water. They are used alone or mixed with other

chemicals for control of crabgrass in turf. Both

are somewhat incompatible with the dinitros.

Lead arsenate is formulated as a paste containing not less than 14 percent AS2O5 or as a powder

containing not less than 32 percent AS2O5. It is

also mixed with chlordane for crabgrass control.

Calcium arsenate can be substituted for lead

arsenate at lower rates of application.

Organic Arsenicals

The organic arsenicals include disodium methylarsonate and amine methylarsonate. Both compounds are considerably less toxic than the inorganic arsenicals to humans and livestock, but

they are harmful if swallowed. Both are applied

postemergence for the control of crabgrass in turf.

Disodium monomediylarsonate (disodium médiane

arsonate hexahydrate)

This compound is designated as DMA by WSA.

It is soluble in water, nonvolatile, and nonflammable. It is formulated as water-soluble powders

containing 50 to 100 percent hexahydrate (31.5 to

63 percent disodium methylarsonate anhydrous),

as 20 to 30 percent hexahydrate aqueous solutions

(12.6 to 18.9 percent anhydrous), and as dry mixtures with vermiculite containing 2.5 to 4 percent

hexahydrate (1.57 to 2.52 percent anhydrous).

Total water-soluble arsenic in the 50- and 100-percent powders is 12.8 and 25.6 percent, respectively. Disodium methylarsonate is compatible

with the salts and esters of 2,4-D.

Amine metiiylarsonate (octyl-dodeq^l ammoníiun

metíiylarsonate)

This compound is unofficially designated as

AMA. It is formulated as an aqueous solution

containing 8 percent octyl ammonium methylarsonate and 8 percent dodecyl ammonium methylarsonate. Total arsenic in water-soluble form is

4.1 percent. It is compatible with 2,4-D and

silvex. In addition to crabgrass, sedge and seedlings of barnyard grass, dallisgrass, and foxtail

can be controlled with AMA.

BENZOIC ACID COMPOUNDS (III)

The benzoic acid compounds are readily translocated in the plant. They kill through both root

and foliage absorption. They are good temporary

soil sterilants for both perennial and annual

weeds.

2,3,6-trichloroben2oic acid

This compound is designated as 2,3,6-TBA hj

WSA. It is a mixture of isomers; 2,3,6 predominates with lower amounts of 2,3,4; 2,3,5; 2,4,5;

2,4,6 ; and 3,4,5. It is formulated as the dimethylamine salt of trichlorobenzoic acid, containing 2

pounds per gallon acid equivalent. It is nonvolatile, noncorrosive, and nonflammable. It is a mild

skin irritant. It is compatible with 2,4-D amine,

dalapon, diuron, and monuron.

This compound is more effective than 2,4-D,

2,4,5-T, or silvex on bindweed, ñeld; bur-franseria; cockle, white; halogeton; knapweed, Eussian ; spurge, leafy ; and thistle, Canada.

Eesistant weeds are: broomsedge; cholla;

greenbrier; hickory; horsenettle, Carolina; maidencane; mesquite, honey; nightshade^ silverleaf;

oak, bluejack, interior live, post, shinnery, and

Turkey; panicum; redcedar, eastern; salmonberry; tarbush; waterchesnut; whitethorn (Acacia) ; and yaupon.

Polychlorobenzoic acid

This compound is designated as PBA by WSA.

It is a mixture of a small amount of 2,3,6-trichlorobenzoic acid and a higher proportion of

several other polychlorobenzoic acid derivatives.

It is formulated as the dimethylamine salts of

polychlorobenzoic acids, containing 4 pounds per

gallon, acid equivalent. It is nonvolatile, noncorrosive, and nonflammable. It is a mild skin irritant. It is compatible with 2,4-D amine, dalapon,

diuron, and monuron.

PBA is more effective than 2,4-D, 2,4,5-T, or

silvex on bindweed, field; bur-franseria; cockle,

white; halogeton; knapweed, Eussian; spurge,

leafy ; and thistle, Canada.

Eesistant weeds are: broomsedge; cholla;

greenbrier; hickory; horsenettle, Carolina; maidencane; mesquite, honey; nightshade, silverleaf;

oak, bluejack, interior live, post, shinnery, and

Turkey; panicum; redcedar, eastern; salmonberry; tarbush; waterchestnut; whitethorn (Acacia) ; and yaupon.

Dicamba (2-medioxy-3,6-dichloroben2oic add)

This compound is formulated as the dimethjrlamine salt of 2-methoxy-3,6-dichlorobenzoic acid

in water, containing 4 pounds, acid equivalent,

per gallon.

Itis very effective on several hard-to-kill broadleaved weeds, such as buckwheat, tartary ; garlic,
HERBICIDE MANUAL 9

wild; knotweed, prostrate; Russian-thistle; smartweed, green; sowthistle, perennial; spurry, com;

thistle, Canada; and wildbuckwheat.

Resistant weeds are: catchfly, nightflowering;

cowcocMe; and falseflax.

CHEMICAL COMBINATIONS

Erbon (2-(2,4,5-trichlorophenoxy) ethyl-2,2-dichloropropionate) (I, b; III, a)

Erbon combines the properties of 2,4,5-T and

dalaçon in a single compound. A typical commercial product is an emulsifiable formulation

containing 4 pounds technical erbon per gallon.

Erbon is moderately toxic to man and livestock.

There is little hazard of poisoning in ordinary

handling, but it may cause skin and eye irritation.

Erbon is translocated, has the properties of a

contact herbicide, and persists in the soil long

enough to kill weed seedlings that germinate after

treatment. Itis effective against both grasses and

nongrasses; hence, it is used to elimmate hand

mowing around guide rails, guide posts, signposts,

and bridges on highways and to control vegetation on tank farms; in lumber yards, railroad

yards, and pulp-piling yards; along fences and

athletic tracts and in similar areas.

Resistant weeds are : bindweed, field ; bracken ;

dandelion; four-o-clock; kochia; milkweed, common; needlerush; nutgrass, purple; purslane,

common; sorrel, red; and thistle, Canada.

FenuronTCA (3-pheayI-l,l-dimethylurea trichloroacetate) (I, b; III; IV)

This compound combines the properties of

fenuron and TCA. Commercially, it is formulated as a 22-percent granular product, a 22-percent pelleted product, and a liquid concentrate

containing 3 pounds active ingredient per gallon.

It is only slightly toxic to mammals, but it is

irritating to skin and eyes. It is readily soluble

in water so that it is easily leached from the soil.

The pelleted product is best adapted for control

of brush and trees, especially hard-to-kill species

such as greenbrier, hickory, and sassafras. The

liquid formulation is used for a foliage spray or

basal and stem applications. It kills topgrowth

more quickly than the dry formulations.

MonuronTCA (3-(p-chlorophenyl)-l,l-dimethylurea

trichloroacetate) (I, b; III; IV)

This compound combines monuron, which is less

soluble than fenuron, with TCA. Commercially,

it is formulated as an 11- and 22-percent granular

product and an oil-soluble liquid concentrate containing 3 pounds active ingredient per gallon. It

is irritating to skin and eyes. The liquid formulation is used for foliage spray.

The period of soil sterilization depends on soil

and rainfall. Both constituents (monuron and

TCA) are readily leached from porous soil in

areas of high rainfall so that the herbicide is not

effective on loose railroad ballast and on sandy

soils in the Southeastern States.

Resistant weeds are: burdock; cotton, wild;

greenbrier; hawthorn; horsetail, field; lantana;

nimblewill; paspalum; poison-oak; smilax; toadflax, yellow; torpedograss; and yucca {Y. smallicma).

COPPER SULFATE (I, IV, V)

Copper sulfate, often called blue vitriol or bluestone, is the most widely used herbicide for the

control of most algae in ponds, lakes, and

streams. It is formulated as a 98- to 99-percent

salt that is soluble in water. It is corrosive to

metals. Large quantities taken into the body may

be fatal and small quantities taken continuously

may be injurious. It is toxic to many species of

fish at concentrations above 1 p.p.m., which is

very close to rates required for aquatic weed control. Toxicity depends on the species of fish, the

hardness of the water, and other factors that influence the amount in solution. The U.S. Public

Health Service considers drinking water with

over 7.5 p.p.m. dangerous for humans and over

100 p.p.m. dangerous for 2-year-old cattle.

Resistant weeds are: algae, Pithophora/ bulrush; coontail, common; pondweed, horned and

sago; sweetgrass, floating; waterplantain, common; watershield; and water-starwort.

2,3,5,6-TETRACHLOROTEREPHTHALIC ACID (I)

This compound is designated as DCPA by

WSA, It is usually called Dacthal on the label.

It is formulated as an odorless water-dispersible

powder containing 75 percent active ingredient.

It is applied preemergence to control crabgrass,

some other annual grasses, and certain broadleaved weeds in established turf. DCPA is not

corrosive. It is nonirritating. It is compatible

with 2,4-D, chlordane, and the dinitros.

Since DCPA affects seeds, it prevents the germination of turf grass seeds if they are sown

soon after the soil has been treated. Among

weeds susceptible to DCPA are: alfilaria; carpetweed; chickweed, common; filaree, redstem; Florida-pusley ; foxtail; lambsquarters; millet, Texas;

panicum ; purslane, common ; and stinkgrass.

Resistant species are: bromegrass, downy;

cheat; dandelion; galinsoga; Jimson-weed; mustard, black and wild; oats, wild; ragweed, common; smartweed, ladysthumb and Pennsylvania;

and velvetleaf.
10 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

DALAPON (2,2-DICHLOROPROPIONIC ACID)

(I, B, C; III, A)

Dalapon is formulated as the sodium salt of

dichloropropionic acid. It is a water-soluble

powder applied in solution for a foliage spray.

A typical commercial product contains 85 percent

of the salt or 74 percent of the acid equivalent.

The acute oral toxicity is low. It is not absorbed

through unbroken skin. Undiluted, it may cause

skin irritation after prolonged contact, but spray

concentrations are not irritating. The powder or

concentrated solutions can cause painful irritation of the eyes.

Dalapon is used principally to control grasses,

but it is also effective against cattails; cine, jack

and white; phragmites; rushes; and white-cedar.

It is a growth-regulator type of herbicide that is

translocated from leaves to roots and rhizomes

of perennial grasses. It is more effective in foliar

applications than TCA, but it is also absorbed by

the roots. For general weed control, it is mixed

with a broad-leaved weedkiller such as 2,4-D,

amitrole, or silvex. Dalapon disappears from the

soil most rapidly in warm and humid regions. It

persists longer in dry cool soils where microbial

activity is low.

Most broad-leaved weeds are tolerant to resistant. Among the resistant species are: algae,

OsGÜlatoria; bracken; euonymus; lotus, American; onion, wild; pagodatree; and waterlily.

DiCHLONE (23-DICHLORO-l,4-NAPTHOQUINONE)

(I, B, C)

Dichlone is formulated as a wettable powder

used for aquatic-weed control. It is chemically

stable, mixes well with oil, and remains active in

water with a pH of 9 to 10. Dichlone does not

kill fish at rates used for an algacide. It is effective on blue-green algae, filamentous green algae,

milfoil, waterweed, hornwort, stonewort, and submersed pondweeds.

Eesistant weeds are : Ohara spp. ; Gladofliora

spp.; fanwort; Hydrodictyon spp.; Lerrma minor; and Zygnema spp.

O- (2,4-DICHLOROPHENYL)-0-METHYL

ISOPROPYLPHOSPHORAMIDOTHIOATE (I)

This compound is designated as DMPA by

WSA. It is formulated commercially as a granular material and as an emulsifiable liquid.

The granular product contains 4.4 percent active ingredient and is used for the selective control of crabgrass and knotweed in established

turf of blue, St. Augustine, centipede, bermuda,

and zoysia grasses. It is less liable than the

liquid formulation to cause foliage burn of turf

The liquid formulation contains 3 pounds of

active ingredient per gallon. It is used for the

selective control of crabgrass; knotweed, prostrate; and nimblewill in established bluegrass

turf. It may stunt bentgrasses or narrow-leaved

fescues and thin stands.

Neither formulation controls buckwheat, tartary; catchfly, nightflowering ; daUisgrass; dandelion; falseflax; purslane, common; quackgrass;

or smartweed, green. Both prevent the growth

of turfgrasses if seeded soon after treatment.

DMPA does not corrode steel, iron, galvanized

iron, or tin. It can cause mild irritation of the

eyes and skin and can be absorbed through the

skin if contact is prolonged. Vapors of highly

concentrated liquid formulations can be harmful

if inhaled.

DiNiTRO COMPOUNDS (I, II, III, V)

The dinitros are contact herbicides used alone

and to fortify oils. The parent compounds do not

dissolve in water but are soluble in oil. Sodium,

ammonium, or amine salt formulations are water

soluble.

The three parent compounds are designated by

WSA as: DNAP, 4,6-dinitro-ö-sec-amylphenol;

DNBP, 4,6-dinitro-ö-sec-butylphenol; and DNC,

3,5-dinitro-ö-cresol.

All three compoimds are yellow dyes that stain

skin, hair, and clothing. They are highly poisonous if swallowed, if absorbed through the skin,

or if any appreciable amoimt of spray mist is

inhaled. Although they are not irritating, they

are readily absorbed through the skin. They

should be kept away from heat and open flame.

The parent compounds are used nonselectively

for topkills of vegetation. The sodium, ammonium, and amine salts are used selectively. The

parent compounds are very effective contact herbicides that control a wide range of herbaceous

plants, including many oil-resistant plants. They

require large amounts of water, and their effectiveness as weedkillers varies widely with the

temperature.

The dinitros are not economical to use on perennial grasses and on coarse, vigorous annual

grasses. Repeated applications are required for

control in areas of long seasons and high rainfall.

DNBP is the most effective form, DNC the

least effective, and DNAP intermediate.

DNBP

Typical commercial formulations contain 5

pounds DNBP per gallon plus 87.9 percent oil

or an alkanolamine salt containing 3 pounds

DNBP per gallon. Ammonium salts of DNBP

contain 1 pound per gallon.

Eesistant weeds are: carrot, wild; chamomile,

stinking mayweed; chickweed, mouse-ear; fennel,

common; mallow, dwarf; and pineappleweed.
HERBIOIDE MANUAL 11

DNAP

Typical commercial formulations contain 75

percent DNAP.

DNC

A typical commercial formulation contains 30

percent sodium salt of DNC. The effectiveness

of DNC can be increased considerably by the addition of ammonium sulfate, aluminum sulfate,

or sodium bisulfate.

DlQUAT (6,7-DIHYDRODIPYRIDO(l,2-A : 2',1'-C)

PYRAZIDIINIUM SALT) (I)

This compound is a nonvolatile and nonflammable contact herbicide used for aquatic-weed

control. Its acute oral toxicity to rats is high.

Fanwort and southern naiad are resistant.

ENDOTHALL (3,6-ENDOXOHEXAHYDROPHTHALIC

ACID) (I, II)

Endothall consists of three isomers, of which

the exo-cis isomer shows the greatest biological

activity. Its acute oral toxicity to mammals is

high, and endothall must be handled with care.

It is sold commercially as a 20-percent water solution containing 2 pounds per gallon of the disodium salt and as a water solution containing

6.3 percent of the disodium salt plus ammonium

sulfate. Endothall is noncorrosive and nonflammable, but it is irritating to the skin.

Endothall is not completely nonselective, but

combined with 2,4-D it provides complete vegetation control. It breaks down rapidly in the

soil so that residual toxicity is short, especially

in the humid areas. It is absorbed by plant roots,

but it may be translocated in some plants.

Eesistant weeds are: catchfly, mghtflowering;

chickweed, common and mouse-ear; goosefoot;

lambsquarters, common; mustard, wild; orache;

purslane, connnon ; radish, wild ; and smartweed,

green.

Both liquid and granular formulations are

used for aquatic-weed control. A typical liquid

formulation is a water solution containing 19.2

percent disodium endothall. A granular formulation contains 5 percent disodium endothall on

an inert clay carrier. Either may be fatal if

swallowed and both are irritating to skin, eyes,

nose, and throat.

They are contact herbicides effective on burreed, coontail, horned pondweed, watermilfoil,

and pondweeds {Potamogetón spp.). In northem areas, Pithophora^ Cladophora^ and Spirogyra algae appear susceptible at the 2 to 5 p.p.m.

rate. Because of its short residual life, treated

areas that have conditions favorable for algae

development may be subject to regrowth within

the season. At rates of 1 to 2 p.p.m., there is a

wide margin of safety for fish.

Eesistant weeds are: Gha/ra spp.; fanwort;

and naiad, southern.

FENAC (2,3,6-TRICHLOROPHENYLACETIC ACID)

a A)

Fenac consists of several isomers, of which the

2,3,6 isomer is the most toxic to plants. It is

considered the active ingredient. It is formulated

as a liquid containing iy2 pounds, acid equivalent,

per gallon (the active ingredient is the sodium

salt) and as a 10-percent granular product. The

acute oral toxicity for rats is moderate, and fenac

is nonirritating if handled with ordinary precautions.

Fenac causes growth-regulator type responses

in plants, but drift hazards are less than with

2,4-D. Effects on plants are slow to appear, especially on deep-rooted perennials. Fenac is persistent in the soil, but conditions favoring microbial activity hasten its breakdown.

Weeds on which fenac has proved effective are :

ash; basswood; bindweed, field; bur-franseria;

franseria, woollyleaf; hogpotato; honeysuckle;

knapweed, Kussian; maple; puncturevine; Russian-thistle; sassafras; sida, alkali; sowthistle,

perennial; spurge, leafy; thistle, Canada; wildbuckwheat; and witchweed.

Eesistant weeds are: bracken; carrot, wild;

nightshade, silverleaf ; nutgrass; and many perennial grasses.

FUMIGANTS

Fumigants are volatile at ordinary soil temperatures and at atmospheric pressure. They are

applied to the soil not only to kill the weeds but

in some instances to kill soil micro-organisms,

nematodes, and insects. There are three general

classes: (1) Those that are mixed with the surface soil, sealed in with water, and do not recluiré

a gasproof cover; (2) those that do require a

gasproof cover; and (3) those that are injected

into the soil.

Carbon disulfide (I)

Carbon disulfide is a volatile liquid slightly

soluble in water. It is highly flammable and

poisonous as a gas. Emulsions or solutions with

alkali (thiocarbonates) are available for soil

treatment. It is very effective against deep-rooted

perennials because the gas is heavier than air and

penetrates deeply into the soil, but it is very expensive for large areas.

Chloropicrin (trichloronitromethane) (I)

Chloropicrin is a colorless, volatile liquid almost insoluble in water. It is highly toxic to
12 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

mammals—an exposure for 30 minutes can be

lethal. It is nonflammable and noncoirosive to

copper, brass, and bronze but attacks iron, zinc,

and other light metals. The gas causes tears and

is irritating to mucous membranes; it is, therefore, used as a warning agent in other fumigants.

Chloropicrin in vapor form kills weed seeds,

nutlets of nutgrass, and soil-inhibiting insects and

micro-organisms. It requires a cover for best results.

Methyl bromide (monobromomethane) (I)

Methyl bromide is a colorless, liquified gas that

is slightly soluble in water. Although it is generally considered nonflammable and nonexplosive,

some mixtures with air can be exploded by a

spark. Both the liquid and gas are poisonous,

and the effects of exposure are cumulative. Contact with skin causes severe burns. It is formulated as a solution in an inert solvent for soil

applications. Usually it is mixed with a volatile

substance that because of its odor or its irritating

or lachrymose properties is a warning of the presence of methyl bromide.

Methyl bromide controls weeds, plant diseases,

and insects in the soil. It is effective on nutgrass

and perennial grasses, but seeds of whiteclover are

resistant. It is used on soils contaminated with

seeds, rhizomes, tubers, and other vegetative plant

parts before seeding turf areas or setting out trees

and shrubs. It is also used for renovating tees,

greens, and fairways on golf courses. It makes

reworking of old turf areas unnecessary. A cover

is necessary to confine the vapor.

3,5-dimethyltetrahydro-l,3,5,2H-thiadia2Íne-2-thione

(I; m, b)

This compound, designated as DMTT by WSA,

is a solid slightly soluble in warm water. A commercial formulation contains 96 percent active ingredient plus a wetting agent.

DMTT breaks down in moist soil and releases

gases and water-soluble materials that control

soil fungi, weeds, and nematodes. It can be applied dry or as a water suspension. When used

without a cover, it is sealed in with about an inch

of water. The use of a cover, however, delays reinfestation after treatment. SMDC (p. 48) is

more effective than DMTT when the water seal

and no cover is used, but with water plus cover,

DMTT is the more effective.

Purple nutgrass is difficult to control even with

high rates.

Sodium-N-methyldithiocarbamate (I; III, b)

This compound, designated as SMDC by WSA,

decomposes in moist soil and becomes toxic to insects and plants. It is readily soluble in water.

A typical commercial formulation contains 4

pounds per gallon. It is toxic to mammals and

irritating to eyes and mucous membranes.

SMDC kills germmating seeds of both grasses

and nongrasses and controls nematodes, soil fungi,

and insects. It can be sprayed on the soil surface

and sealed in with water without a cover. Its

residual toxicity disappears in about 2 weeks. It

is used for preplantmg treatment of seedbeds,

potting soil, and areas for ornamentals and nursery stock, orchards, vineyards, and turf.

HYDROCARBONS, INCLUDING CHLORINATED

HYDROCARBONS

Aromatic solvents (I; V)

These products are also called solvent napthas

or petroleum napthas. They include a variety of

petroleum and coal distillates that can be used in

heavy concentrations for aquatic-weed control.

Kerosene, especially as sold in eastern United

States, mineral spirits, tractor distillate, lowgrade diesel oil, and similar aliphatic materials

do not control submersed weeds. Most effective

products are those with a flash point above 80"^ F.,

distillation between 278° and 420° F., and an

aromatic content of at least 85 percent. These

solvents are highly flammable and irritating to

the skin and eyes or when inhaled. Livestock

tend to avoid drinking treated water. Vegetation

is not harmed when irrigated with treated water.

Aromatic solvents are deadly to fish. They are

used in irrigation and drainage ditches especially

in short ditches (6 to 8 miles or less) with even

sides and bottoms and with flows of 1 to 70 c.f.s.

Acrolein (pp. 6 and 56) is more practical in

longer ditches. They are often mixed with emulsifiers to form a stable emulsion in the water.

Chlordane (l,2,4,5,6,7,8,8-octachloro-4,7-methane-3a,

4,7,7a-tetrahydromdane; 1,2,4,5,6,7,8,8-octachlor2,3,3a,457,7a-hexahydro-4,7-methanoindene) (I)

Technical chlordane contains 60 percent octachloro-4,7-methanotetrahydroindane and 40 percent related compounds. The mixture is required

to contain 64 percent chlorine of compounds soluble in benzene. It is insoluble in water. It is

absorbed through the skin and is harmful if

swallowed or inhaled. Chlordane is formulated

as 25- to 75-percent emulsion bases, 40- to 50-percent dusts, and 10-percent granules. Originally

an insecticide, it is also used for the preemergence

control of crabgrass in turf.

Herbicidal oils (I, d; II)

These compounds are used as vegetation topkillers, as solvents in the formulation of herbicides, and as carriers for herbicidal chemicals.

Oils that kill by contact should not be used as

solvents or carriers of translocated herbicides,

since a quick kill of the conducting tissue prevents translocation of the chemical.
HERBICIDE MANUAL 13

Oils vary widely in their composition, value for

herbicides, and flammability. Generally, the toxicity to plants is greater with increased content

of aromatics. Aside from composition, the value

for herbicides is influenced by some physical

properties. If the boiling point is low, the oil

may evaporate too rapidly; if too high, it does

not penetrate plant tissues. The viscosity, or

flowing quality, should permit use in cool weather.

Specific gravity is important in aquatic-weed control. The flammability is indicated by the flash

point; the lower the temperature at which an oilvapor-air mixture ignites, the greater the danger

of explosion. A weed oil that meets the following specifications is satisfactory for nonselective

use.

Aromatics Minimum 50 percent

Boiling range 302° to 527° F.

API gravity 20° to 30°

Flash point Minimum 180° F,

For convenience in handling during cold

weather, the oil should have a maximum pour

point of -10° F. Oils below API 27° are heavy

and do not pour well in cold weather. However,

if oils are too light—above API 38°—^they do not

have the persistent action needed for chronic poisoning. There are five general classes of oils.

(a) Medium-to-heavy, viscous, aromatic oils

for general weed control : diesel oils, burner oils,

low-grade oils, and oil extracts. They are safe

to use and noncorrosive. Diesel oil is available

commercially as diesel fuel oil. It varies in aromatic content depending on degree of refinement.

Usually it is an effective contact herbicide. Lowgrade oils are available only from local refineries

m some oil-producing regions; only limited

amounts of oil extracts are available.

(b) Light oils not toxic to all plants and used

for selective weed control : stove oil, kerosene distillate, Stoddard solvent, and mineral spirits.

They are low in aromatic content.

(c) Special oils resulting from the manufacture of gasoline and formulated especially for

weed control. Many oils of this type are now

available, but they are also low in aromatic content.

(d) Fortified oils, whose herbicidal properties

have been increased by the addition of pentachlorophenol, dinitrocresol, dinitrobutylphenol, or

octachlorocyclohexanone.

(e) Emulsifiable oils; oil solutions containing

a surfactant capable of causing emulsification

upon mixing with water. The oils, in general,

are moderately toxic to animals, but kerosene

types are highly toxic.

Oil sprays wet leaf surfaces and penetrate waxy

leaf surfaces more effectively than water sprays,

are less easily washed off the plant, and evaporate

more slowly under high temperatures. The effect

of oils on perennials is temporary. Oils are used

for a quick kill of topgrowth—a chemical substitute for mowing. They penetrate the leaves of

nongrass plants, but kill grasses by creeping

down the stem to the crowns and roots. Kepeated

treatments are necessary where seasons are long

and rainfall is high. The cost depends on distance from source of supply. If relatively nontoxic, large volumes are necessary especially for

oil-tolerant species and aerial applications are

impractical. Some of the disadvantages of the

oils used alone can be overcome by fortifying

them with phenol compounds or using them in

conjunction with soil sterilants. The necessary

volume can be reduced, the toxicity to tolerant

weeds can be increased, a wider range of oils can

be used, and the initial kill can be hastened, but

the cost is raised.

The fortified oil sprays in low volume are effective on small weeds. When plants, especially

grasses, are tall enough to protect their crowns,

larger spray volumes are required. Emulsions

provide larger volume although they do not increase toxicity to plants. The oil content can be

varied—10 percent for easy-to-kill species and

up to 25 percent for hard-to-kill species. Frequently, a fortified oil emulsion is more economical than a straight oil emulsion. Oils used as

solvents or carriers may or may not be toxic to

plants.

The fortified oil emulsions are well suited for

killing all vegetation on roadsides, ditchbanks,

and similar places and for spot treatment of shallow-rooted perennials. The staining that may

result from oils carrying the dinitros when used

on sidewalks and driveways is objectionable.

Weed oils are preferred for such use and for oiltolerant weeds.

As a class, oils are insoluble in water; when

mixed with water in the presence of a surfactant,

they form an emulsion. The common emulsion

has oil dispersed in water; an invert emulsion is

the reverse—water is dispersed in the oil. The

fortifying chemical is dissolved in either the

water or the oil or both.

Kesistant weeds are : chamomile, stinking mayweed; cocklebur, common; cowparsnip; duckweed, common; fennel, common; Florida-pusley;

foolsparsley; mallow, dwarf ; milkweed, common;

pineappleweed {M. matricarioides) ; poison-hemlock ; redvine ; St.-Johns-wort, Klamath-weed ;

and star-thistle, yellow.

MALEIC HYDRAZIDE (1,2-DIHYDROPYRIDAZINE3,6-DIONE)

This compound is designated as MH by WSA.

It is used to reduce mowing expense, since it retards the growth of some grasses. It is formulated as a sodium salt—a water-soluble powder
14 AGRICULTURE HANDBOOK 269, U.S. DEPT, OF AGRICULTURE

containing 40 percent MH equivalent and a dietlianolamine salt—a water-soluble liquid containing 3 pounds per gallon of active ingredient.

Both formulations are only slightly toxic to man

and animals.

Johnsongrass, yellow nutgrass, and wild onion

are resistant.

MIXTURES

Amitrole-simazine (III, a)

In this mixture, the simazine is added to provide residual toxicity after the quick knockdown

of vegetation by the amitrole. This mixture is

more effective than amitrole alone for pole yards,

parking areas, gravel shoulders and center strips

on highways, lumberyards, around buildings,

transmission towers, guardrails, bridges, and on

similar areas. It does not corrode spray equipment, is nonflammable and odorless, and does not

stain.

Weeds resistant to both amitrole and simazine

are resistant to the mixture.

Borate-monuron

This mixture is designated as BMM by WSA.

A proprietary mixture containing 63.2 percent

disodium tetraborate pentahydrate, 30.8 percent

disodium tetraborate decahydrate, and 4.0 percent

monuron is available. The B2O3 equivalent of the

boron compounds in this mixture is 41.4 percent.

Both constituents are only slightly toxic to mammals. The formulation is a granular product that

is nonflammable and noncorrosive. The boron

compounds are effective on broad-leaved plants,

and monuron is an effective grasskiller. It is slow

in action and is resistant to breakdown by soil

micro-organisms.

Resistant weeds are : maidencane ; needlegrass;

purslane, common; rose, prairie; smartweed,

Pennsylvania ; and toadflax, yellow.

Borate-2,4-D

This mixture is designated as BDM by WSA.

A proprietary mixture containing 55 percent disodium tetraborate pentahydrate, 35.5 percent

disodium tetraborate decahydrate, and 7.5 percent 2,4-dichlorophenoxyacetic acid is available.

It is applied dry. It is nonpoisonous when used

as directed and is noncorrosive and nonflammable.

The mixture is designed to kill deep-rooted,

perennial, broad-leaved weeds. It is not recommended to control grasses. It results in quicker

topkills than borates alone. In semiarid regions,

residual toxicity lasts 1 to 2 years at rates of 121/^

to 141/^ pounds per 1,000 square feet. It is resistant to attack and decomposition by soil organisms, but it is leached below the root zone in soil

when exposed to heavy rains.

Chlorate-borate (I, d; III, b)

This mixture is designated as CBM by WSA.

A proprietary mixture containing 73 percent disodium octaborate and 25 percent sodium chlorate,

with a B2O3 equivalent of 49 percent is available.

It may be applied dry or as a spray. It is completely soluble in water. Its oral toxicity is low.

It is noncorrosive to ferrous metals, and the borate in the mixture is a fire deterrent.

This mixture combines the rapid contact action

of chlorates with the more persistent toxicity of

the borates. The residual toxicity may last 3 to 5

years at rates of 25 to 30 pounds per 1,000 square

feet in semiarid regions, but it varies with soil

type and rainfall. In spray form, the mixture

acts as a contact herbicide, killing topgrowth,

and is also absorbed by plant roots.

Eesistant weeds are: ceanothus, Jersey-tea;

daisy, English; hawksbeard, smooth; and sowthistle, annual.

Chlorate-borate-monuron (I, d; III, b)

This compound is designated as CBMM by

WSA. A proprietary mixture of 40 percent sodium chlorate, 54 percent sodium metaborate, and

2.4 percent monuron is available. Itis formulated

as a powder for both dry and wet application and

as a granular product.

The sodium chlorate and boron compounds are

effective against deep-rooted, perennial broadleaved weeds, and monuron is effective against

grasses. The mixture is a long-lasting soil sterilant that is nonpoisonous to mammals. The borate in the mixture is a fire retardant, but some

precautions are necessary to avoid a fire hazard.

Kesistant weeds are: ceanothus, Jersey-tea;

daisy, English; hawksbeard, smooth; hawkweed,

orange; needlegrass; nightshade, black; nutgrass, purple and yellow; panicum; and sowthistle, annual and perennial.

Qilorate-chloride (I, d)

The herbicidal properties of this mixture are

similar to those of sodium chlorate (p. 19), since

the chlorate is the active ingredient. The chloride

is added to reduce the fire hazard of the chlorates.

Although the fire hazard of the mixture is less

than that of sodium chlorate alone, dry accumulations on clothing, wood, or other organic matter

may be flammable. Precautions as outlined for

sodium chlorate should be observed (p. 36). Eates

are based on the amount of chlorate in the mixture. It may be used dry or as a spray.

Weeds resistant to sodium chlorate are also

resistant to this mixture.

Daiapon-silvex (I, b; III, a)

An emulsifiable formulation containing 4

pounds dalapon plus one-half pound silvex per

gallon is available commercially. The diethylene
HERBICIDE MANUAL 15

:lycol ester of dalapon and the propylene glycol

lutyl ether esters (low volatile) of silvex are

used. The mixture is noncorrosive and nonpoisonous, but it may cause skin irritation.

It is nonselective and translocated. It is not so

dependent on rain as those herbicides that are

absorbed by plant roots. It is most effective when

plants are growing rapidly. Ee-treatment or spot

treatments are usually necessary for seasonal control, since it does not have a long residual toxicity

in the soil. Drift is a hazard to plants nearby.

Weeds resistant to both dalapon and silvex are

resistant to the mixture.

OCTACHLOROCYCLOHEXENONE (I)

This compound is designated as OCH by WSA.

It is a mixture of isomers so has no precise physical properties. It is highly toxic. It is formulated as a 40-percent solution of petroleum oil.

It is used to kill duckweed.

PENTACHLOROPHENOL (I, II, III, V)

This compound is designated as PCP by WSA.

It is a contact herbicide used alone and to fortify

oils. It is used for topkills of vegetation, but it

is considerably less effective than the dinitros

over a wide range of plants and is more difficult

to handle. Effectiveness on weeds can be increased by adding ammonium sulfate, aluminum

sulfate, or sodium bisulfate. The oil formulation

is destructive to rubber. PCP is not compatible

with calcium arsenate.

PCP is highly poisonous if swallowed, if absorbed by the skin, or if appreciable amounts of

spray mist are inhaled. Since both the powder

and spray mist are very irritating to the nose

and throat and cause violent sneezmg, and since

swallowing would induce immediate vomiting, absorption through the skin is the most likely way

for PCP to enter the body. The powder and

water solutions are irritating to the skin, but the

chemical is readily absorbed.

PHENOXY COMPOUNDS (III, A; V)

The phenoxy compounds include 2,4:-D, MCPA,

2,4,5-T, and silvex. In the acid form, these herbicides are only slightly soluble in water. For

commercial use, they are formulated as esters,

which form milky emulsions with water and also

dissolve in light oils, or as water-soluble salts.

The amines are the most widely used salts. They

are easily soluble in water and are commonly

sold in liquid form. There are also sodium and

ammonium salt formulations that are sold as

water-soluble powders, but they are not so effective as the amine salts on hard-to-kill species or

on weeds that are in bud stage and beyond. All

of the salts are practically nonvolatile. Two

general kinds of esters are commercially available : relatively high-volatile esters and relatively

low-volatile esters. Although the low-volatile

esters vaporize less rapidly than the volatile esters, both types are volatile at high temperatures.

Drift can occur with any of the formulations if

the spray is in very fine droplets or mist and

there is a wind.

The phenoxy formulations are moderately toxic.

The hazard to livestock and wildlife is negligible

on treated vegetation, but toxic amounts could be

eaten if animals had access to undiluted concentrates or large amounts of spray mixtures. As

ordinarily handled, these materials are not likely

to cause irritation to skin or eyes. They are not

absorbed through the skin to any appreciable

extent, and, in the amounts likely to be inhaled^

are not hazardous. Neither is the ingestion oi

harmful amounts likely. At dosages used for

weed control, they may harm fish in still, shallow

water. They are noncorrosive and nonñammable.

2,4-D (2,4-dichIorophenoxyacetic acid)

2,4-D is formulated as water-soluble sodium,

ammonium, or amine salts and volatile or lowvolatile esters. Sodium salts and esters are also

available as dusts. A new formulation is the

diamine salt. It is an oil-soluble amine that has

the weedkilling properties of an ester and the

nonvolatile features of amine salts. It is formulated in a concentrate containing 2 pounds, acid

equivalent, per gallon.

2,4-D is used for the control of herbaceous

broad-leaved weeds. It can be applied at extremely low concentrations compared with the

inorganic herbicides, such as borates and chlorates. It is absorbed through leaves and is readily

translocated in the plant, but it is also absorbed

by plant roots. It is commonly used as a selective

herbicide rather than a soil sterilant. Its effect,

when applied to the soil, is temporary except under very dry conditions or cool weather. It is

more effective on broad-leaved weeds when applied as a foliar spray than on grasses, although

in some areas it has killed grass seedlings when

applied in large amounts to the soil.

2,4-D is used on many perennial broad-leaved

weeds, since it is translocated to the roots and

underground storage organs. It is carried with

the sugars as they move out of the leaves. It is,

therefore, most effective on warm sunny days

when photosynthesis is active. It is a very useful

herbicide to kill annual nongrass weeds that frequently re-infest an area treated with a soil sterilant after it has leached below the surface layer.

It is also an inexpensive and convenient chemical

to kill certain weeds that are tolerant to a soil

sterilant. On roadsides and similar areas where

grasses are desirable for erosion control and in
16 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

turf, 2,4-D can be used selectively to kill broadleaved plants in sod. 2,4-D is also effective on

certain broad-leaved aquatic plants.

2,4-D is also used for the control of w^^^^J

plants. The salt formulations are practically

nonvolatile but, with the possible exception of

the diamine salt, are less effective than the esters

on hard-to-kill species. The low-volatile esters

are equally as effective as the volatile esters and

in some instances are better. Some woody species

are tolerant to 2,4-D but susceptible to 2,4,5-T

and vice versa. For use on mixed populations,

the two herbicides are combined in a formulation sold as "brush killers." These brush killers

contain one-third to one-half 2,4,5-T and twothirds to one-half 2,4-D. Brush killers are also

effective on poison-ivy, poison-oak, and poisonsumac.

The esters are used extensively in oil for basalbark, stump, and cut-surface applications. Diesel

oil, kerosene, and water are used as carriers. They

are used in the fall and winter on deciduous trees

when there are few active leaves present or in the

summer to increase penetration of leaves, bud

scales, and bark. Water is commonly used as the

carrier with ester in emulsion for foliage sprays.

Only small amounts of oil can be used for this

latter purpose (up to 10 gallons per acre), since

oil kills leaf tissue and hence prevents movement

of the chemical to the roots.

2,4-D is more effective than MCPA on buckbrush, snowberry ; ceanothus, wedgeleaf ; chamise ;

chickweed, common, field, and mouse-ear; cinquefoil, common and sulfur; cocklebur; dock, broadleaf and curly ; flixweed ; garlic, wild ; gooseweed ;

gromwell, com; ground-ivy; hawkweed, orange

and yellow; heal-all; Indian hemp; knapweed,

diffuse; knotweed, prostrate; lupine, silvery;

mallow, little; manzanita; milkvetch; nutgrass;

oak, post and white ; onion, wild ; pineappleweed

{M. matrioarioides) ; poison-oak; poorjoe; puncturevine; purslane, common; rabbitbrush, grey;

rose. Macartney ; rush ; sage, creeping ; sagebrush,

big; sorrel, heartwing and sour dock; speedwell;

sumac, Chinese; tansy; toyon; tree-of-heaven ;

vetch, narrowleaf ; and wormwood, annual.

Resistant species are : agrimony ; algae, Mycrocystis; artichoke thistle; ash; aster, western and

woody; barberry, Allegheny; barnyard grass;

basswood; bedstraw; beech; bermudagrass; betony, Florida; blackberry; bluebell; bluestem,

little ; bouncing-bet; bracken ; bristlegrass; bromegrass; broomsedge; buckwheat, tartary; buffalobur; bugleweed, creeping; bumet; buttercup,

bulbous; calendula; campion; catchfly; chamomile, corn; cheat; cherry; chinquapin, golden;

cockle, white; coriander; corncockle; cowcockle;

crabgrass; cudweed; deadnettle, red; dodder;

duckweed; elm; false-chamomile; ñeídmadder;

fir, balsam, red, and white; foxtail; fimaitory;

goosefoot, spear-leaved; goosegrass; gourd, buffalo; goutweed, bishops; greenbrier; gromweil,

common; groundcherry, clammy and smooth;

groundsel, common; gum, black; hawksbeard;

hawthorn; hemlock; hempnettle; henbane; henbit; hickory; hogpotato; honeylocust; horsebrush,

littleleaf ; horsenettle; horsetail, field; huisache;

iohnsongrass; juniper; knapweed, Kussian;

knawel; ladysmantle; larkspur, duncecap, little,

and tall; mallow, common; manzanita, greenleaf;

maple; marigold, corn; mayweed, scentless; medusahead; mesquite, honey and velvet; milkweed,

climbing, common, showy, western, and whorled;

mint, field and water; mugwort; mulberry; mullein, common; needle-and-thread; nightshade,

silverleaf; nimblewill; oak, black, blackjack,

bluejack, canyon live, interior live, and scrub;

oats, wild; Osage-orange; panicum; paspalum;

pellitoryweed; persimmon, common; pine, jack,

Jeffrey, lodgepole, red, and white; plum, chickasaw; prickly-ash; quackgrass; queensdelight; redbay; redbud; redcedar, eastern; redtop; redvine;

rescuegrass; rocket, London; rose, California,

multiflora, and Woods; St.-Johns-wort, Klamathweed; salmonberry; saltcedar; sandburs; sandspurry; sedge; sida, alkali; smartweed, green and

swamp; smutgrass; sorrel, red; spikerush; sprangletop; spruce, white; spurge, flowering, leafy,

upright, and com; squirreltail; strawberry, wild;

sweetgrass, floating; sweetgum; tanoak, scrub;

thistle, wavyleaf ; toadflax, yellow; violet; whitethorn, mountain; windmillgrass, tumble; woodsorrel, yellow ; yarrow ; yaupon ; and yucca, soapweed.

MCPA (2-methyl-4-chlorophenoxyacetic acid)

MCPA contains several isomers, but the 2-

methyl-4-chloro isomer is the most effective for

killing weeds. Therefore, the better formulations

contain a high proportion of this isomer. The

most widely used formulations are the sodimn

and amine salts.

MCPA is very similar in use to 2,4-D. It is

used for the control of herbaceous broad-leaved

weeds. (See under 2,4-D, p. 15.)

MCPA is more expensive than 2,4-D. However, it is more effective than 2,4-D on artichoke

thistle ; buckwheat, tartary ; burcucumber ; buttercup; coffeebean; hempnettle; hickory; honeysuckle; horsetail, field; knapweed, spotted;

pepperweed, perennial; St.-Johns-wort, Klamathweed ; spurry, com ; and yarrow, common.

Eesistant species are: alligatorweed; ash;

aster, woody; bedstraw, cleavers and smooth;

blackberry; bluemustard; bouncing-bet; bracken;

buckbrush, snowberry; l3uffalo-bur; bugleweed;

bumet; buttercup, bull30us; calendula; campion,

bladder; catchfly, nightflowering; chamise; chickweed; cockle, white; comfrey, common; coriander; corncockle; cowcockle; deadnettle, red;
HERBICIDE MANUAL 17

dodder; elm; garlic, wild; gooseweed; grapehyacinth; greenbrier; gromwell, corn; groundcherry, smooth; groimd-ivy; groundsel, common;

halogeton; hawksbeard, smooth; hawkweed, orange and yellow; hawthorn {Urataegus spp.) ;

heal-all; henbit; hogpotato; horsenettle; Indian

hemp; knapweed, diffuse and Russian; knawel;

knotweed, prostrate; ladysmantle; larkspur,

duncecap and tall; lupine, silvery; mallow, common and little; manzanita; maple; marigold,

corn; mayweed, scentless; mercury, annual; mesquite, velvet; milkweed, common, showy, and

western whorled ; mint, water ; mugwort; mullein,

common; nutgrass; oak, blackjack, bluejack, interior live, post, scrub, and white; onion, wild;

pellitoryweed; poison-oak; poppy; purslane, common; rabbitbrush, grey; redvine; rocket {Frcmsería) ; rose. Macartney and multiflora ; sagebrush, big ; saltcedar ; sandspurry ; sedge ; smartweed, green; smilax; sorrel, red; speedwell;

spurge, leafy; squirreltail; strawberry, wild;

sumac, Chinese; tansy; thistle, wavyleaf; toadflax, yellow; tree-of-heaven; violet; and woodsorrel, yellow.

2,4,5-T (2,4,5-trichlorophenoxyacetic acid)

2,4,5-T is generally used in the ester formulation although there are sodium and triethanolamine salts. There is also a new diamine formulation containing 2 pounds, acid equivalent, per

gallon ; 2,4-D and 2,4,5-T are also combined in a

formulation called "brush killer." The diamine

salt brush killer contains 1 pound, acid equivalent, of 2,4-D plus 1 pound, acid equivalent, of

2,4,5-T; other brush killers contain the esters in

combinations of one-third to one-half 2,4,5-T to

two-thirds to one-half 2,4-D.

2,4,5-T can be used for the selective control of

broad-leaved weeds in turf and for some emersed

aquatics of nongrass species, but it is used principally for the control of woody plants. Like

2,4-D, it is a growth-regulator type of herbicide

that can injure nearby broad-leaved plants

through drift. Handling precautions are the

same as for 2,4-D. The salt formulations are

practically nonvolatile but, with the possible exception of the diamine salt, are less effective than

the esters on woody plants. The low-volatile

esters are equally as effective as the volatile esters

and in some instances are better.

Some woody species are tolerant to 2,4,5-T but

susceptible to 2,4-D and vice versa. Brush killers

are used on mixed populations.

Eesistant species are: arrowhead {8, longiloba) ; artichoke thistle ; ash ; aster, western and

woody; barnyard grass; bedstraw; beech; bermudagrass; betony, Florida; bluestem, little;

bouncing-bet; bristlegrass; bromegrass; broomsedge; buckbrush, snowberry; buckeye, California; buffalo-bur; campion; carpetweed; catchfly.

nightñowering ; cheat; chinquapin, golden ; cockle,

white; comfrey, common; corncockle; cowcockle;

crabgrass; dodder; duckweed; foxtail; garlic,

wild; goosegrass; greenbrier; groundcherry,

smooth; groundsel, common; halogeton; hawkbit; hawksbeard; hawkweed, orange and yellow;

heal-all; hemlock; hogpotato; horsebrush, littleleaf; horsetail, field; huisache; Indian hemp; iris.

Rocky Mountain; johnsongrass; juniper; knapweed, diffuse and Russian; knawel; larkspur,

little and tall; mallow, common; manzanita,

greenleaf; medusahead; mercury, annual; milkweed, common, showy, and western whorled;

mountain-mahogany; mugwort; mulberry; needle-and-thread ; nightshade, silverleaf; nimblewill; nutgrass; oak, canyon live, interior live,

and turbinella; oats, wild; onion, wild; paspalum; pine, jack, Jeffrey, red, and white; pentstemon; pineappleweed {M, matrhcaHoides) ;

quackgrass; rabbitbrush, grey ; redbud ; redcedar,

eastern; redtop; redvine; rescuegrass; rocket

(Franseria) \ sandburs; smutgrass; sorrel, red;

speedwell; spikerush, creeping ; sprangletop ;

spruce, white; spurge, leafy, upright, and corn;

squawberry; squirreltail; strawberry, wild; tanoak, scrub; toadflax, yellow; umbrella-sedge;

Virginia-creeper; yaupon; and yucca, soapweed.

Silvex (2-(2,4,5-trichlorophenoxy)propionic acid)

Silvex is an organic acid that is formulated as

a low-volatile ester, a liquid potassium salt, and

a granular product.

When emulsified with water or an oil-water

carrier, the ester formulation is used as a selective

translocated foliar spray to control many broadleaved weeds and some woody plants. Commercial products are formulated of mixed propylene

glycol butyl ether esters, a butoxyethanol ester,

or an iso-octyl ester of silvex to contain 4 pounds,

acid equivalent, per gallon. Undiluted, the

esters are very painful to the eyes and irritating

to the skin; but in diluted spray mixtures, they

are only mildly irritating. In acute oral toxicity,

they are similar to esters of 2,4-D and 2,4,5-T.

Ester formulations of silvex are used in much

the same way as esters of 2,4,5-T except that

(1) they are safer where drift onto cotton is a

hazard, (2) they are more effective as a foliage

spray on maple, redbud, Cherokee rose, saltcedar,

and trumpetcreeper, (3) they are not so effective

for basal-bark and cut-surface applications, and

(4) they are more effective on mouse-ear chickweed, henbit, and yucca.

Resistant species are: ash; aster, western and

woody; bluestem, little; blueweed, Texas;

bracken; broomsedge; buckbrush, snowberry and

coralberry; buckeye, California; buffalo-bur; calendula; campion, bladder ; caraway; carpetweed;

catchfly, nightflowering ; chamise ; chinquapin,

golden; corncockle; cowcockle; deathcamus.
18 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

grassy; dock, curly; dodder; duckweed; elm;

garlic, wild; gooseweed; greenbrier; groundcherry, smooth; groundsel, common; halogeton;

hawksbeard, smooth; hawthorn; heal-all; hogpotato; horsetail, field; iris, Kocky Mountain;

juniper; knapweed, diffuse and Kussian; larkspur, little; mallow, common; medusahead; needle-and-thread ; nightshade, silverleaf ; nutgrass;

oak, interior live; pineappleweed {M, matricarioides) ; plum, chickasaw; rabbitbrush, grey; redbay; redvine; rocket (Franseria) ; rose, Woods;

sandburs; smartweed, green; smilax; snakeroot,

white; snakeweed, broom; snowbrush; speedwell;

spikerush, creeping ; sprangletop ; squawberry ;

sweetgrass, floating; tanoak (L, densiflora) ;

toadflax, yellow; umbrella-sedge; and waterchestnut.

The liquid salt formulation is a solution of the

potassium salt of silvex containing 6 pounds,

acid equivalent, per gallon. It is used to control

aquatic weeds. This formulation is less toxic

than the ester formulations to fish except brown

trout. It does not injure land plants growing

adjacent to treated areas. It is similar to 2,4-1)

in its effect on many species of submersed aquatic

weeds and is more effective on some. Handling

precautions are similar to those for the ester

formulations.

The granular product contains 20 percent acid

equivalent. It is used to control the same

aquatic weeds as the liquid salt. Handling precautions are similar to those for the liquid salt

and esters except that there is more danger of

inhaling dust and less danger of skin irritation.

Toxicity to fish is the same as for the liquid salt.

Aquatic weeds susceptible to silvex are : arrowhead, coontail, fanwort, parrotfeather, pickerelweed, primrose-willow, spatterdock, water-hyacinth, waterlilies, watermilfoil, waterplantain,

watershield, water-stargrass, and water-starwort.

PHENYLUREA COMPOUNDS (I, B, C; III, B, C)

The substituted phenylureas used for soil sterilants include monuron, diuron, and fenuron.

They are only slightly soluble in water; low in

volatility ; noncorrosive ; and nonflammable. They

are formulated as water-dispersible powders,

granular products, liquids, and pellets. With the

exception of the pelleted and granular materials,

all forms are applied as suspensions in relatively

large volumes of water and require agitation in

the spray tank.

Although these chemicals do not move far laterally in the soil, they may be washed down the

surface of slopes to kill vegetation below and they

leach deeply enough to reach the roots of trees,

shrubs, and other deep-rooted plants growing under the treated area. All three chemicals can

irritate eyes, nose, throat, and skin.

Monuron (3-(/?-chlorophenyl)-l,l-dimedi7lurea)

Monuron is formulated as a water-dispersible

powder containing 80 percent active ingredient.

It is also formulated as a granular material.

The effects of monuron on all weeds are slow

to appear. Monuron is more effective in light

sandy soils than in heavy types at equivalent rates

and is more active in mineral soils than those

high in organic-matter content. It is much more

soluble in water than diuron, so it is better

adapted to areas of less than 25 inches of

rainfall a year except along irrigation and drainage ditches. It is also preferred to diuron for

soils containing considerable amounts of clay,

especially bentonite, or of organic matter. At

high rates, it leaches readily from sandy sous

and moves downward twice as fast as diuron in

both clay and sandy soils. It is somewhat more

effective on grasses than nongrasses and gives

better control than sodium chlorate. Heavy rainfall and standing or running water; conditions

favoring microbial activity such as warm soils

of high organic-matter content and moisture; and

soil cultivation shorten its persistence in the soil.

Sterility of the soil may last 1 to 3 years; this

depends on rates applied, soil type, and rainfall.

Eesistant weeds are: bracken; burdock, great;

carrot, wild; cocklebur; coltsfoot; dandelion;

horsetail; nimblewill; nutgrass, purple; paspalum; plantain; and yucca {Y. smallictna).

Diuron (3-(3,4-dichlorophenyl)-l,l-dimethylurea)

Diuron is even less soluble in water than monuron. It is formulated as a water-dispersible powder containing 80 percent active ingredient.

There is also a liquid suspension, containing 2.8

pounds per gallon, active ingredient.

The effects of diuron on all weeds are slow to

appear. Diuron is more effective than monuron

where rainfall is over 25 inches a year and especially on sandy soils. It is not recommended for

areas of low rainfall, especially to control deeprooted plants. Larger amounts of diuron than

monuron are adsorbed by all soils; consequently,

it is more persistent.

Eesistant weeds are: bracken; burdock, great;

carrot, wild; cocklebur, common; coltsfoot; dandelion; dock, veiny; elderberry; horsetail, field;

nimblewill; paspalum; and yucca (Y, smallicma).

Fenuron (3-pheayl-l,l-dimethylurea)

Fenuron is more soluble in water than monuron

or diuron, but still only small amounts can be dissolved (0.02 lb. per gal. water). It is formulated

as a 25-percent pelleted product. It is inactivated

more rapidly than monuron or diuron and is

adapted as a soil sterilant only for dry areas.
HERBIOIDE MANUAL 19

PHENYLMERCURIC ACETATE (I)

This compound is designated as PMA by WSA.

It is a solid only slightly soluble in water. It is

used both as a herbicide for the control of crabgrass in turf and as a fungicide to control some

turf diseases. The most common formulation is

a liquid containing 10 percent PMA. It is extremely poisonous if taken internally and can

cause severe bums on the skin.

SODIUM CHLORATE (I, D)

When unmixed with other chemicals, sodium

chlorate is readily soluble in water. Because it

strongly supports fire, it is frequently mixed

with soluble borates or calcium chloride to reduce this hazard. The solubility of the mixtures

is considerably less than sodium chlorate alone.

Sodium chlorate is relatively nontoxic to man and

animals unless consumed in large quantities. Because of its salty taste, sodium chlorate may increase the palatability of poisonous plants that

would not otherwise be eaten by livestock.

Sodium chlorate is an inexpensive, long-lasting

soil sterilant in dry areas and a relatively temporary one in humid areas. The rate of decomposition is hastened by high temperatures and adequate moisture, which are favorable to microbial

action; it is readily leached in coarse-textured

soils; it is not readily absorbed by plants in soils

high in nitrates or salts. It is absorbed by active

roots in moist soil but not by dormant roots in

dry soil. With adequate rain, chlorate is distributed throughout the soil profile, but in dry soils

the chlorate is confined to the upper layers.

Nitrates, which prevent absorption of the chlorate by plant roots, are also accumulated in these

layers. The effectiveness of sodium chlorate is

also reduced by a high organic-matter content

and a high pH of the soil. It is generallj^ applied

to the soil, but it can be used as a foliar spray

for a quick topkill. It may be translocated when

applied as a foliar spray. It is highly toxic to

many plants, but there are resistant species.

Eesistant weeds are: bracken; camels-thorn;

gorse; heliotrope, wild; kochia; poison-oak; rescuegrass; sida, alkali; and sweetgrass, floating.

The most important disadvantage of sodium

chlorate is its flammability when in contact with

organic matter, sulfur, sulfides, phosphorus, powdered metals, strong acids, or ammonium salts.

When stored in paper or cloth sacks or when dry

on clothing or vegetation after spraying, it may

be ignited by friction, a spark, or even the heat

of the sun. It burns so rapidly that the operator

can be injured severely or buildings destroyed

before the fire can be extinguished. In spite of

the danger of handling sodium chlorate, large

quantities are used safely by following the proper

precautions.

TRIAZINES (III, B, c)

The triazines include simazine and atrazine.

These are soil sterilants when applied at high

rates. They are noncorrosive, nonflammable, and

present no electrical or conductivity problem

around utilities, power plants, transformers, signal blocks, or other electrical installations.

Simaziiie (2-chloro-4,6-bis(ethylamino)-s-triazine)

Simazine is practically insoluble in water. It

is formulated as an 80-percent water-dispersible

powder and as a 4-percent granular product.

Both formulations are used for the nonselective

control of vegetation on areas where any plant

growth is undesirable. The granular product is

also effective against rooted aquatic plants such

as coontail, fanwort, horned pondweed, and watermilfoil.

Simazine is adsorbed by soil colloids. High

cation-exchange capacity, high organic-matter

content and, to a less extent, high clay content

of soils reduce its toxicity to plants. It is probably also deactivated by soil micro-organisms.

Simazine has little or no contact action on foliage, so there is no drift hazard. It cannot penetrate an unbroken leaf cuticle and is absorbed

only through the roots. Simazine is ineffective

until water carries it to the root zone, and its

action is slow. It is easily removed from equipment by washing. It forms a suspension in water

that requires agitation to keep the chemical from

separatmg out.

Eesistant weeds are : barberry ; bindweed, field ;

blackberry; buttercup, creeping; dock, veiny;

dogwood; golden-aster, false; hemlock; johnsongrass; knapweed, Eussian; milkweed, common;

nutgrass, purple and yellow; pine, white; rose,

multiflora ; spurge, leafy ; thistle, Canada ; vaseygrass; and white-cedar.

Atrazine (2-chloro-4-ethyIamino-6-isopropylamino-stxiazine) (III, a)

Atrazine is formulated as an 80-percent waterdispersible powder and a 4-percent granular product. It is more soluble than simazine, so that it

is more effective in dry areas. Weeds better controlled with atrazine than simazine are: horsetail; Indian hemp; lettuce, prickly; nutgrass,

yellow; rush; sedge; and thistle, Canada.

Atrazine, unlike simazine, is absorbed through

plant leaves; hence, there is a drift hazard. It is

slightly more toxic than simazine to mammals

and remains toxic in the soil for a slightly shorter

time.

TRICHLOROACETIC ACID (I, B, C; IV)

This compound is designated as TCA by WSA.

It is readily soluble in water. It is formulated as

the sodium salt containing 94 percent active in-
20 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

gredient and 82.8 percent acid equivalent and as

a liquid containing 5 pounds per gallon, acid

equivalent. In the liquid form it tends to decompose and liberate chloroform. In warm storage

it may expand to the extent of damaging the containers. Solutions of 10 percent or more may

burn skin and eyes unless washed off immediately.

There is no practical hazard to livestock from

eating or contacting sprayed foliage. In concentrations of 10 percent or more, TCA corrodes

low-quality steel, galvanized iron, zinc, aluminum,

and brass.

TCA is used to control grasses. It is not so

effective as dalapon in foliar applications, but it

is somewhat more persistent in the soil. It disappears through leaching and microbial activity.

It is so soluble that it is quickly leached by heavy

rainfall and in well-drained soils. It is also adsorbed in clay and organic soils and disappears

more slowly from muck than sandy soils. For

mixed populations of broad-leaved and grass

plants, some broad-leaved weedkiller is added.

The effectiveness of TCA is greatly increased by

tillage; rates of application can be reduced from

one-half to two-thirds by tillage.

Most of the broad-leaved weeds, including bitterweed, false golden-aster, purple nutgrass,

pagodatree, and vaseygrass, are resistant.

HERBICIDES AND MIXING OF SPRAY MATERIALS

Some herbicides can be used as they come from

the manufacturer. Such chemicals as sodium

arsenite or sodium chlorate can be applied dry

or need only to be dissolved in water. Others,

however, are practically useless in their original

form and require formulation before they can be

used for weed control.

FORMULATIONS OF HERBICIDES

A formulation contains the herbicide in a form

that can be (1) dissolved or suspended in a carrier and distributed in solution or suspension by

sprayers, (2) distributed dry by dusters or

spreaders, or (3) easily vaporized for fumigation.

Often an emulsifier, spreader, sticker, or other

surfactant is added to facilitate dilution or increase wetting capacity. Frequently formulations

contain an inactive filler that serves as a diluent

only. For example, there may be only 2, 3, 4, or

6 pounds of active weedkiller in a herbicide

formulation that weighs 10 pounds per gallon.

There are several types of formulations.

Water-Soluble Concentrates

Water-soluble concentrates are readily dissolved

in water to make a spray. They are often sold as

solids. TCA, dalapon, sodium salt of 2,4-D, and

amitrole are examples. They are also formulated

as liquids—amine salts of 2,4-D or MCPA and

the sodium salts of PGP and endothall. These

liquid formulations are prepared because some

water-soluble chemicals cannot be handled conveniently unless they are diluted. For example,

the alkanol amine salt of 2,4-D is soluble in water,

but at room temperature it is a heavy viscous

liquid that would be difficult to measure or mix

with water and when cool it becomes stiff and

unpourable. It is formulated into a free-flowing

liquid that can easily be diluted with water and

is convenient to handle. Water-soluble concentrates are also available as pastes and slurries—

sodium salts of DNC, POP, and 2,4-D. They

may or may not include wetting agents.

Emulsifiable Concentrates

Emulsifiable concentrates are usually liquids in

which the chemical is dissolved in one or more

water-insoluble solvents such as oil or benzene

and to which an emulsifier is added. When the

emulsifiable concentrate is added to water and

agitated, the mixture is broken into fine droplets.

The emulsifying agent causes the fine droplets

of oil to be suspended in the water to form an

emulsion. The esters of 2,4-D, 2,4,5-T, and silvex

are examples. The formulation should be clear,

homogeneous, and free from sediment or crystalline solids. It should not corrode equipment, and

the flash point should not be lower than 140° F.

Since emulsions are frequently used in cold

weather, the concentrate should have a maximum

pour point of -10° F.

The emulsifiable concentrate should disperse

readily. A concentrate having poor dispersibility emulsifies only with vigorous agitation and

free oil usually separates from the emulsion on

standing a short time. A good emulsion has globules that are barely visible; one with globules so

fine they cannot be seen with the naked eye is better. Such an emulsion is called tight.

The breaking time of an emulsion is also important. Some formulations produce emulsions

that break in a few minutes after application,

others remain stable for 24 hours. The fastbreaking emulsion requires constant agitation and

does not wet leaves adequately. Where constant

agitation is impracticable, such an emulsion settles in the tank. Very stable emulsions may not

break soon enough, especially in brush spraying,

and they tend to drain off the leaf. A good

emulsion should contain the solvents and emulsifying agents necessary to keeç it stable with hard

or soft water during the mixing and application

period but to allow it to break soon after reaching the plant surface. As an average, the hardness of water is 322 p.p.m. in terms of calcium

carbonate for hard water, 115 p.p.m. for water
HERBICIDE MANUAL 21

in municipal systems, and 35 p.p.m. for rainwater.

Emulsifiable concentrates should be stable under both hot and cold storage.

Invert emulsions are water-in-oil mixtures in

which every spray droplet is surrounded by oil

instead of water. This results in a viscous material difficult to apply but less likely to drift.

Oil-Soluble Concentrates

Oil-soluble concentrates are similar to emulsifiable concentrates, but they do not contain an

emulsifier. They do not mix with water, but they

can be diluted with fuel oil or kerosene or applied without dilution. PGP and DNBP are

examples.

Powders and Pastes

Wettable powders or water-dispersible powders

are generally formulated from chemicals that are

insoluble or soluble with difficulty in oil or water.

They are finely ground with or without a powdered diluent. A wetting agent is added to keep

the particles from floating, and a dispersing

agent is added to keep the material in suspension.

Monuron, diuron, and simazine are examples.

2,4-D, 2,4:,5-T, and MCPA have been formulated

as powders and pastes.

Dusts

Dusts are dry herbicides plus a filler. The sodium salt of 2,4-D is formulated as a dust.

Granules and Pellets

Granules and pellets are forms of herbicides in

which the chemical is impregnated upon vermiculite, attaclay, or similar carriers. They can be

prepared by spraying the herbicide on the carrier

or by adding the core material, such as vermiculite, to the original dry powder. Then a pillrolling technique with binders is used to produce

pellets, or the powder plus binders and water is

extruded, chopped, and dried to produce grains

or pellets. Fenuron, simazine, 2,4-D5 and an increasing number of herbicides are formulated as

pellets. No water and no mixing are required,

application equipment is less expensive than

sprayers, there is no drift hazard, and they can

be applied in areas awkward for spray equipment. If the chemical is effective only by root

absorption, a spray intercepted by leaves is wasteful; grains or pellets that drop to the ground are

more effective. However, their cost is higher, they

are not adapted for foliar applications but must

be applied to the soil, they are generally less

effective than sprays where moisture is limited,

and distribution of small amounts is difficult except by hand.

Fumigants

Fumigants contain the base chemical and sometimes a lachrymal additive that serves as a warning that poisonous vapors are present. Methyl

bromide, DMTT, and SMDC are examples.

Surfaaants

Surfactant is a general term for wetting agents,

spreader-stickers, and other materials that alter

the physical and chemical characteristics of a

spray solution. A surfactant may serve as an

emulsifier, improve suspension and dispersion of

insoluble powders in water, or improve wetting

through the reduction of surface tension. A realization of the importance of these additives is increasing. The interaction between surfactant and

herbicide appears to be more important than the

effect of the surfactant on surface tension in some

instances.

A good emulsifier must be soluble in both oil

and water or the emulsion will settle out. Wetting agents may increase greatly the entry of a

spray into the leaf. Thejr also prevent precipitation of calcium, magnesium, and iron salts of

2,4-D in hard water. Common concentration is

about 0.1 percent of the spray. Spreader-stickers

help sprays to stick, spread, and cover. Household detergents have similar effects.

PURCHASE OF HERBICIDES

Adequate specifications for the purchase of

some herbicide materials are now being developed.^ They are difficult to write. Basically, the

economic value of a herbicide depends upon the

relative amounts of active chemical toxic to plants

that are contained per pound or gallon. This is

expressed in percent of active ingredient, acid

equivalent, or phenol equivalent for solids and

pounds per gallon for liquids. Thus, a solid containing 74 percent of the weedkilling ingredient

is worth more than a 20-percent granular product

pound for pound, and an amine salt formulation

of 2,4-D containing 4 pounds per gallon, acid

equivalent, is of more value than the same formulation containing 2 pounds per gallon. Actually,

since mixing charges and cost of containers,

freight, and handling have to be paid on twice

as much material for a 2-pound-per-gallon formulation as a 4-pound formulation, the cost per

pound of active material is less in the 4-pound

formulation than in the 2-pound formulation although the cost per gallon of product is more.

1 Federal specifications for use by Federal agencies in

procuring amitrole, dalapon, 2,4-D, simazine, and 2,4,5-T

have been approved.
22 AGRICULTURE HANDBOOK 269, U.S. DBPT. OF AGRICULTURE

But this relationship is affected by other factors: Under some circumstances 1 pound of

2j4-D in the ester formulation is twice as effective

as 1 pound of the amine salt. This could be true

on hard-to-kill species, on many brush species,

and in arid climates. Equivalent amounts of the

sodium salt are less effective than the amine salts.

The amount of chemical that can be packed into

a formulation is limited both for physical and

chemical reasons and from an economic standpoint.

Some herbicides are mixtures of several isomers. Often one is more effective than the others.

Although it may not be economically practicable

to purify a formulation for the effective isomer,

there may be larger proportions of it in one formulation than another. For example, the 2-

methyl-4-chlorophenoxyacetic acid isomer of

MCPA is more toxic to plants than the 2-methyl6-chloro isomer, and, among the polychlorobenzoics, the 2,3,6-trichlorobenzoic acid is more effective on most species than the 2,3,4- ; 2,3,5- ; 2,4,5,- ;

2,4,6- ; or 3,4,5-trichlorobenzoic acids.

Additives, such as wetting agents, spreaderstickers, cosolvents, and emulsifiers, influence the

effectiveness of a chemical. Their precise role

and comparative values, however, are not too well

understood and purchase at present must depend

largely on empirical information. Carriers of the

chemical also vary in cost and in toxicity to

plants. Some can reduce the effectiveness of the

chemical.

The proprietary mixture of two or more chemicals may be less effective than the constituents

applied separately. Because better timing of application can be made of each constituent applied

separately than applied together, the effectiveness of the mixture may be less than the sum of

individual effects.

The purchase of herbicide formulations at present depends on the relative amounts of active

chemical per unit, packaging, freedom from foaming and precipitation problems, and stability under storage. Sometimes the superiority of a formulation can be demonstrated because of these

factors. When Federal specifications become

available, purchase can be made on the basis of

the requirements stated in the specification.

MIXING OF SPRAY MATERIALS

Mixing spray materials correctly involves calculations of the proper amounts of herbicide and

diluent and procedures for mixing.

Calculations

Eates of application are expressed in terms of

acid equivalent for certain herbicides such as

2,4-D, 2,4,5-T, 2,3,6-TBA, TCA, dalapon, and

silvex; phenol equivalent for the dinitros; and

active ingredient for others, such as amitrole and

simazine. They are recommended in ounces or

pounds per square foot, square rod, or acre where

the area to be treated can be measured.

Where spot spraying of individuals or small

clumps of plants is necessary or where dense

foliage, as in brush or trees, is to be thoroughly

wet, the concentration of the spray is recommended in pounds of active ingredient or acid

equivalent per 100 gallons. Also, in the control

of aquatic weeds, concentration of the herbicide

is often referred to in terms of parts per million

of water. This means the number of parts (by

weight or volume) of the chemical in 1 million

parts of water or other diluent.

1 acre-foot of water weighs 2,722,500 lb. ; that

is, 43,560 sq. ft.Xl ft.=43,560 cu. ft.X62 lb.

=2,722,500 lb.

Therefore, 1 p.p.m.=2.7 lb. chemical in 2,722,500

lb. water (1 acre-ft.).

To determine number of pounds chemical required, use the following:

X (pounds chemical) =p.p.iii.xacre-ft.x2.7

Example: Eate, 5 p.p.m.; volume, 1 acre 2 ft.

deep, then X=5X2X2.7=27.

Therefore, 27 lb. of chemical would be required

for 5 p.p.m.X2 acre-ft.

Usually the pounds of active ingredient or acid

equivalent per gallon are given on the label of

liquid herbicide. The percent is given on labels

of powders, granules, and other dry materials.

To calculate the amoimt of liquid herbicide required when the rate is expressed in pounds per

acre use the following formula :

Rate in pounds per acre

pounds of herbicide per gaUon =gallons per acre

Example : If the rate is 1% pounds per acre and

the herbicide contains 4 pounds per gallon, then

1 5

j^=0.37 gallon, or 8 pintsX0.37=3 pints.

Use the same formula to calculate gallons of

herbicide per 100 gallons of spray.

Example: If the rate is 2.5 pounds per 100 gallons and the herbicide contains 2 pounds per

2 5

gallon, then-^=1.25 or ll^ gallons.

To calculate the amount of dry product required when the rate per acre is given, use the

following :

100

percent active ingredientX^^*® P®^ acre=pounds product
HERBICIDE MANUAL 23

Example : If the rate is 15 pounds, active ingredient, per acre, and the percent of active ingredient is 75, then ^X15=20.

Amounts of liquid herbicide or of dry material

to use per acre in various concentrations and for

various rates of application are given (table 2).

A list of equivalents in measures, weights, and

rate of speed is given (Appendix, p. 83) for convenience. Equivalent temperatures on Centigrade

and Fahrenheit scales are given in the "Appendix," p. 83.

TABLE 2.—Amounts of liquid concentrate or of wettdble powder to use per acre m various concentrations

and for various rates of application

Concentration Concentrate to use per acre at the rate of—

of herbicide

2 oz. 4 oz. 8 oz. 12 oz. lib. 2 1b. 3 1b. 4 1b.

Pounds per gaUon of water : i

1 _

Pints

1.0

.67

.50

.34

.25

.20

.17

.14

.125

.11

.10

Pounds 3

1^

10 oz.

S% 0?.

71/^ oz.

5 oz.

4 oz.

3 oz.

2^4 oz.

Pints

2.0

1.3

1.0

.67

.50

.40

.34

.30

.25

.22

.20

Pounds 2

21/2

l^Ä

171/2 oz.

15 oz.

10 oz.

8 oz.

6 oz.

41/2 oz.

Pints

4.0

2.6

2.0

1.3

1.0

.80

.67

.60

.50

.45

.40

Pounds 2

5

2%

2

1%

1^

1

11 oz.

9 oz.

Pints

6.0

4.0

3.0

2.0

1.5

1.2

1.0

.90

.75

.67

.60

Pounds 2

7

3^^

3

2%

1%

1%

1

i2y2 oz.

Pints

8.0

5.3

4.0

2.7

2,0

1.6

1.3

1.1

1.0

.9

.8

Pounds 2

10

5

21^

2

m

1%

Pints

16.0

10.6

8.0

5.3

4.0

3.2

2.6

2.3

2.0

1.8

1.6

Pounds 2

20

10

6%

5

4

2%

21/4

Pints

24.0

16.0

12.0

8.0

t).0

4.8

4.0

3.4

3.0

2.7

2.4

Pounds 2

30

15

12V2

10

71^

6

4

3%

Pints

32.0

1% - 21.3

2 16.0

3 10.7

4 _ 8.0

5 6.4

6 - 5.3

7 4.6

8 ~ 4.0

9 3.6

10 3.2

Percentage of dry material :

10 _ _

Pounds 2

40

20 20

25

10

30

40

50 8

75

90 ^

1 In active ingredient, acid equivalent, or phenol equivalent.

2 To be added to the water or other liquid to be sprayed on 1 acre.

Procedure

To calculate capacity of the sprayer tank

(all measurements in inches) :

Cylindrical tanks: Multiply lengthXsquare of

diameterX0.0034:==capacity in gallons.

Tanks with elliptical cross section: Multiply

lengthXshort diameterXlonger diameterX

0.0034=capacity in gallons.

Kectangular tanks with square or oblong cross

section : Multiply lengthXwidthXdepthX

0.004329=capacity in gallons.

Never pour the concentrate into an empty

tank. Either fill the tank half full, add the

chemical, agitate, and complete the filling or

start filling and add the chemical as the filling

is continued. Operate the sprayer with the nozzles shut off bypassing the spray through the tank

for several minutes (at least six times) to insure a thorough mixing.

Water Sprays

When using a soluble powder or crystals, fill

the tank half full of water. Add the chemical

slowly, and stir to dissolve it completely- If a

detergent is recommended, add one-quarter to

one-half pound of household detergent per 100

gallons spray- If a solid grasskiller is to be

used with 2,4-D or 2,4,5-T, mix it with water

first and then add the 2,4-D or 2,4,5-T. Use the

spray solution within 1 or 2 days after mixing,

since some chemicals lose strength on standing.

If an amine salt of DISTBP is used in very

hard water, add 1 pound softener per 100 gallons spray.

Emulsions

Since emulsions are suspensions and not solutions, they require constant agitation. If no

additional oil is to be used, start running water

into the empty tank and slowly add the herbicide formulation with continuous agitation. The
24 AGRICULTURE HANDBOOK 269, U.S. DEPT. OP AGRICULTURE

chemical should all be added by the time the

tank is one-third full.

If oil is to be used, premix the herbicide and

the oil in a separate container. Do not allow

any water to get into this mixture or it may jell.

Fill tank one-third full of water, add premixed

oil and herbicide, and continue filling. Agitate

constantly. The water should be clean and low

in carbonates and sulfates. (If ordinary hand

soap lathers well, the water is satisfactory.)

Circulate the mixture until it is uniformly white.

If the emulsion stands for several hours, stir until uniformly white before using. Take samples

of the emulsion from various sections of the

tank at intervals to determine if separation has

taken place.

When an invert emulsion is used, add water

slowly to the premixed herbicide-oil solution under constant mechanical agitation; circulating

with bypass is insufficient. Invert emulsions

may separate readily on standing. After 24

hours of separation, most invert emulsions cannot be restored.

Oil Sprays

Add esters of 2,4,5-T, 2,4:-D, or silvex, or

other oil-soluble herbicides to the required

amount of oil and mix thoroughly in the tank.

This can be done at any time before spraying,

since the spray does not separate. Do not let

any water or any oil-water mixture get into the

chemical formulation or the herbicide-oil mixture or it may jell.

Suspensions

Water-dispersible powders mix readily with

water but do not dissolve. There are two methods of mixing: (1) add the powder slowly to

water, with agitation—it should not be added to

an empty tank—or (2) make a thin water slurry

of the required amount of material before it is

added to the water in the tank. A thorough job

of mixing will help the agitator do its job more

efficiently.

When esters of 2,4-D are used with monuron

or diuron, add one-half pound of a caseinate

conditioning agent to the suspension before adding the 2,4-D ester.

Wlien a water-soluble chemical is to be mixed

with a water-dispersible powder, dissolve the

water-soluble chemical in the water before adding the powder.

STORAGE OF HERBICIDES

A chemical with a low flash point (140° F. or

less) is dangerous in storage.

Deterioration of chemicals in storage can be

prevented by observing the following precautions.

Dusts and wettable powders present no problem as long as they are kept clean and dry.

They cake when wet, and packages may deteriorate. Water-soluble solids also cake when

wet and when subjected to great changes in

temperature. If packages are left open, hygroscopic chemicals become wet by absorbing

water from moist air. Such chemicals as TCA,

dalapon, PCP, chlorates, borates, and ammonium sulfamate cake when they are wet.

Liquid formulations should be stored on pallets or duckboards to avoid rusting of the metal

containers. The containers should be kept

tightly closed. Where air vents have been

punched in cans to facilitate pouring, they

should be plugged. Even small amounts of water introduced into emulsion concentrates or oil

solutions can cause them to jell and cause deterioration of the container.

Chemicals may crystallize out of solution at

temperatures below 32° F. If this happens,

warm the products to 40° F. or higher and roll

drums or shake containers. If the crystals return to solution, no harm has been done. The

following formulations do not freeze if stored

in unheated rooms : Low-volatile esters of 2,4-D,

2,4,5-T, 2,4-D plus 2,4,5-T (brush killer), and

silvex and the alkanol amine salt of DNBP.

The following formulations may freeze if stored

at temperatures below those indicated:

o p

2,4-D, alkanol amine salt 15

2,4-D, dimethylamine salt 20

2,4-D, butyl ester 23

2,4-D, isopropyl ester 32

2,4,5-T, butyl ester 47

2,4,5-T, amine salt 34

2,4-D plus 2,4,5-T, butyl ester 18

2,4-D plus 2,4,5-T, amine salt 43

MCPA, amine salt 14

DNBP, emulsifiable oil concentrate 20

DNBP, ammonium salt 32

At high temperatures, chemicals may expand

and cause bulging of drumheads and leaks in

the containers. They may deteriorate at temperatures over 95 "^ F. High temperatures may

reduce the effectiveness of emulsifiers and hasten

the corrosion of containers.

APPLICATION EQUIPMENT

The results that follow the use of a herbicide

depend largely on how well or how poorly it is

applied, and this in turn depends on the operator and his equipment. Equipment is designed

to apply herbicides (1) wet, in sprays or mists,

(2) dry, in dusts or granules, and (3) in readily

vaporized form for fumigation.
HERBICIDE MANUAL 25

DESCRIPTION

Ground Sprayers

Hand Sprayers

Hand sprayers are suitable for treating small

patches, inaccessible areas, and fence rows; for

spot spraying; and for situations where the

spray is to be applied close to susceptible plants.

They include sprinkling cans, compressed-air

sprayers of 1- to 5-gallon capacity carried by a

strap over the shoulder, and knapsack sprayers

with hand-operated pump. In the ordinary compressed-air sprayer, the pressure is reduced as

the tank is emptied; but there are constant-pressure types. Some models, useful on trails, have

cylinders of CO2 gas to provide pressure. Kjiapsack sprayers are more expensive than compressed-air sprayers, but they have an agitator

attached to the pump that makes them more

suitable for suspensions.

Trombone-type sprayers are very versatile.

They are especially adaptable for spraying tall

trees.

Water-dispersible powders that form suspensions of high concentration in water tend to clog

flat spray tip nozzles; a cone type gives less

trouble. Compressed-air and knapsack sprayers

are well adapted for herbicide concentrates to

be used along highways. The cone oil-burner

type nozzle that delivers 2.5 to 6 gallons per

hour at 20 to 30 p.s.i. is very suitable. The solution or emulsion at 20 times usual concentration is applied at the rate of 5 to 6 gallons per

acre for low-growing vegetation or 12 gallons

per acre for heavier brush. A hood around the

wand or boom prevents drift onto sensitive

plants nearby.

Boomless Sprayers

Boomless sprayers—^nozzle-cluster type-^-are

well adapted for spraying roadsides and ditchbanks, under utility lines, and along fence rows.

They are less expensive, simpler to operate, and

have less nozzle trouble than boom sprayers.

They can pass between trees and shrubbery, they

can be maneuvered close to other obstacles, and

they are practical for rough ground. They

spray a broadcast swath of 20 to 30 feet with

large volumes that provide moderately good

coverage.

For foliage sprays, the conventional equipment consists of a piston-type hydraulic sprayer,

such as the Hardie, Bean, Iron Age, or Myers,

equipped with 3^-inch high-pressure hose and

15 g.p.m. (gallon per mmute) pumps for a

% 6-inch nozzle opening or 35 to 60 g.p.m. pumps

for 14-inch, %6-inch, and 1%6-inch nozzle openings. The equipment is mounted on a fourwheel-drive power wagon or caterpillar-type

tractor. The chief disadvantage of the boomless sprayers is that the spray stream is greatly

affected by the wind. They should not be used

when the wind may cause drift to sensitive vegetation nearby.

Boom Sprayers

Boom sprayers are adapted for large areas

where complete coverage is necessary or for turf

areas adjacent to a road where the entire application can be made from a tractor or truckmounted boom.

For roadside or ditchbank spraying, arm

booms are available. One end of a shaft is fastened to the truck and the other end terminates

in a boomless sprayer nozzle. A two-nozzle arm

boom is used for ditchbanks. A larger boom

can be set at right angles to the truck for roadside or ditch spraying or vertically to spray

above tall weeds. For roadside spraying, two

or more nozzles are grouped together and

mounted on an arm that reaches over mailboxes,

highway signs, etc. A boom mounted on a truck

designed to spray under guide rails reaches over

them and sprays from the outside toward the

pavement. Nozzles mounted off center enable

the operator to spray 15 to 20 feet on one side.

Hand booms and adjustable spray guns are

operated from truck-mounted power spray equipment and are used for application of basal sprays

and stump treatments, for brush control and

spot treatments, and for spraying around structures of various kinds. Handguns are used with

pressures of about 100 p.s.i. Increased pressures

result in a larger proportion of fine droplets and

drift is increased. Handguns can vary delivery

from a broad mist to a narrow coarse stream.

Instead of a single nozzle, a bank of three to

eight can be used. Sometimes the conveyor

truck is stationary and long lines of hoses and

side hoses are used to reach the area to be

treated.

Mist Blowers

Mist blowers are power-driven machines that

disperse highly concentrated sprays in finely

atomized form at low volumes per acre. The

herbicide is carried principally in an airstream

instead of a liquid. These sprayers are free

from boom and nozzle troubles and are very useful to spray herbaceous weeds and woody plants

in swamps, under fences, around stone piles,

along roadsides, in drainage ditches, and under

powerlines. Mist blowers require minimum

amounts of water, they cover vegetation rapidly, and they can be used for areas inaccessible

to power equipment. The equipment is cheaper
26 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

than the conventional hydraulic power equipment. Use of mist blowers for weed spraying,

however, is limited hj the serious hazard of

drift. Mist blowers in 5- to 12-h.p. (horse

power) sizes are useful for brush spraying, if

drift is not a problem. A 2-h.p. knapsack mist

blower is useful for brush up to 30 feet tall, for

spot spraying, and for re-treating.

Special Equipment

For spraying berm and adjacent weeds and

brush: A right-hand drive truck with four nozzles mounted on a 6-foot sturdy vertical beam.

A low-position, solid-stream nozzle with a %6-

inch opening sprays berm to 24 feet from the

machine and three fan-type boomless nozzles

spray brush and weeds close to the machine.

The pump delivers up to 20 g.p.m. at 800 p.s.i.

from a three-speed power takeoff. The whole

operation is controlled by the driver of the

truck. The sprayer delivers from 25 to 50 gallons semiconcentrated material per mile of road.

For spraying around guard rails and posts:

A truck-mounted tank with power sprayers and

a boom mounted on the right side of the truck.

The boom is controlled by an operator sitting

next to the driver. The control valve is handoperated. There are two nozzles, one sprays on

each side of the guard rail or post.

For treating shoulders or fireguards : A boom

operated hydraulically or electrically makes it

possible to raise or lower it over obstructions,

posts, and slopes. The boom for shoulder applications is about 8 feet long and for fireguards,

12 feet.

For basal-stem treatment : A 4-h.p. gas engine

and %-inch gear pump, and two lines of light

hose with suitable nozzles, gun, and shutoff valve

attached to each line of hose. The spray is five

times the concentration of dilute sprays. A simple device is a 2-gallon can—called a "trickier"

—carried on the operator's back, that allows the

chemical to flow by gravity through a flexible

tube to a light wand. The discharge is controlled by a leakproof valve.

For brush, briers, and small trees in fence

lines and on ditchbanks: A tractor-powered,

high-pressure sprayer for spraying foliage. It

may be equipped with nylon-roller or other highpressure pump, 25 feet of high-pressure hose,

and an adjustable spray pattern handgun.

Individual Parts

Pumps.—The capacity of the pump should be

about twice the nozzle delivery rate to provide

for an overflow that is bypassed back to the

tank for agitation of the spray. The several

types are as follows:

1. A rubber-impeller pump is cheap, is not injured by abrasive suspensions, develops about 35

p.s.i.5 but is not adapted for oils.

2. A rotary gear pump has positive action.

The discharge rate depends on the speed of rotations. Suspensions are hard on the gears.

Plastic gear pumps can be replaced more cheaply

than repairing permanent equipment.

3. A centrifugal pump is a single-rotating

impeller type. It pumps a large volume of spray

but does not develop a high pressure—40 p.s.i.

to 70 p.s.i. It can handle all spray materials

with minimum wear. It is not self-priming so

must be mounted lower than the tank. Unlike

most pumps, it pushes the liquid in one direction only.

4. A piston pump is designed for large quantities of spray and high pressures—^up to 1,000

p.s.i. It has one or more plungers connected to

a crankshaft. The plungers or pistons work inside smooth cylinders. The piston pump can be

used for any type of sprayer, stands rough treatment, and IS long lasting but expensive.

5. A nylon-roller pump gives good service, but

it is expensive and is not well adapted for suspensions. It pumps only after reaching a high

speed.

6. A diaphragm pump is similar to a piston

pump except that one side of the chamber is

made of a flexible fabric that creates the vacuum. This pump handles abrasives well, but

the fabric does not always last long under the

pressure normally required for spraying. The

diaphragm, however, can be replaced easily and

economically.

Tanks,—^Tanks should be easy to clean and

rustproof. Other desirable features are: a wide

mouth with 12- to 16-mesh removable strainer;

a round or trough-shaped bottom with a drain

in the lowest part; a paddle-type agitator that

moves slowly, sweeps the bottom, and can be

disengaged; and an auxiliary 1- to 3-gallon

graduated flush tank for quick flushing of the

spray line and that can also be used for small

quantities of spray. The tank should be calibrated in 5-gallon increments with an unpainted

and unvarnished measuring stick. A shutoff

valve should be placed immediately below the

tank to prevent spray material from settling in

the spray line, strainers, and nozzles.

Pressure regulators.—Bypass regulators are

necessary for gear, nylon-roller, diaphragm, and

reciprocating piston pumps; diaphragm regulators, for centrifugal or impeller pumps. The

bypass regulator allows excess liquid to flow

back to the tank; with proper adjustment it can

maintain a constant pressure at the nozzles.

Neither a spring-loaded ball-type high-pressure

relief^ valve nor a hand-operated bypass valve

functions correctly as a pressure regulator. The
HERBICIDE MANUAL 27

regulator should be a sensitive spring-loaded

type for high pressures and a disk or diaphragm

type for pressures up to 175 p.s.i.

Valves^ pressure gage^ and strainers.—The shutoff valves should be fast, easily accessible, and of

the same diameter as the main boom line. Dripping may be reduced or prevented by (1) special

spring-activated valves that automatically close

with reduced pressure, installed between each

nozzle and the boom, or (2) venturi tubes and

shutoff valves, arranged to cause a suction from

the nozzles into the boom when the supply is cut

off.

The pressure gage should be mounted where it

is easily seen by the operator and should be large

enough to be read easily.

Strainers in the boom line should be placed so

as to intercept solid particles before they reach

pump, pressure regulator, or nozzle. A 50- to 80-

mesh screen should be installed in the suction line

to the pump. A strainer of 100- to 150-mesh and

about 100 square inches in area should be placed

between pressure regulator and boom when emulsions or solutions are used. Nozzles require individual screens; a 50-mesh for tips of greater capacity than 0.1 gallon per minute and 100-mesh

for smaller tips. Nozzle screens should have mesh

openings only slightly smaller than the nozzle

opening, so ime particles may pass through.

Hoses and fittings.—^Hoses should be strong

enough to withstand the pressure to be used and

of a material not deteriorated by spray solutions

and oil. Ordinary garden hose stands about 70

p.s.i. The hose on the intake side of the pump

should be at least one-half inch in diameter. The

discharge hose from pump to pressure regulator

should be of the same size. The discharge hose

from the pressure regulator to the nozzles can be

smaller, but it must be large enough to feed at

least twice the number of nozzles being used.

Too small a hose results in reduced pressure at

the distant nozzles. Pipe fittings should be resistant to corrosion. Eyelet fittings are more desirable than welded.

Booms.—Booms should be adjustable for

height, and the tube that carries the spray should

be noncorrosive. In booms with large diameters,

the spray liquid does not flow so rapidly as in

those with smaller diameter. When a suspension

is used, the powder may settle in the boom if the

flow is too slow. Valves at the outer ends facilitate cleaning. Dry booms are supports for a separate hose or tube that carries the spray liquid to

the nozzles. Small booms can be used for hand

sprayers instead of a wand. A funnel slipped

over the nozzle on the end of a wand confines the

spray to a small area and prevents contact with

nearby plants.

Nozzles.—Nozzles are of two general types—

those with removable tips and those whose tips

are an integral part of the nozzle. Removable

tips are convenient. Tips are designed to produce

a flat, fan-shaped spray or a cone-shaped spray.

The fan-shaped is the more accurate in volume

delivery and produces a spray that covers more

uniformly than the hollow-cone type on the average boom sprayer. The fan-type with tapered

edges sprays more uiiiformly on a boom than the

preemergence or band-spray type with squared

edges. Cone-shaped nozzles do not clog so easily

as flat spray types, especially when the spray is a

suspension.

Broadcast nozzles spray a wide swath. They

are used singly and in clusters to cover a v/idth

of 20 to 30 feet and, under some conditions, up to

60 feet. Uniform spray patterns are difficult to

obtain, especially if there is a wind.

The most widely used fan-type nozzles are the

flat atomizing group of which Tee-Jet is an example. They come in spray angles of 110° to 15°

or even in a solid stream. Spacing on a boom is

usually 20 inches. On the nozzles of some companies, the first two digits of the number on a

flat-spray tip indicate the spray angle, the latter

two indicate the capacity in gallons per minute at

40 p.s.i. Numbers on cone-spray tips designate

the capacity only at 10-, 40-, or 60-pound pressure

and depend on the tip design. The spray angle

is directly associated Avitli design and the line

pressure and is stated in the manufacturer's specifications.

Flooding types of flat-fan nozzles deliver a

spray whose droplets are about one-half larger

in diameter than those delivered by the conventional flat-fan nozzles. The conventional flat-fan

nozzles produce a spray pattern of larger droplets

than those produced by the hollo^v-cone or fullcone types.

The smaller the opening, the finer the droplets

if the nozzle design and pressure are the same.

Larger openings can be used for any method of

application by (1) widening the nozzle spacing

on the boom, (2) increasing the spray volume per

acre, (3) increasing the rate of travel, or (4) decreasing the pressure.

Use flat-spray offcenter %-inch tips for ditchbank weeds. Use i/4-inch offcenter tips for directed basal sprays. Use two small fan-type tips

in a double swiveled nozzle for hard-to-wet foliage instead of one larger sized tip ; e.g., two 8002's

instead of one 8004.

Aerial Sprayers

The obvious advantages of aerial spraying are

offset to some degree by the hazards to the pilot

and the damage from drift. A complete discussion of aerial equipment may be found in Concentrated Spray Equipment, Mixtures and Application Methods, by Samuel F. Potts, Caldwell, N.J.,
28 AGRICULTURE HANDBOOK 269. U.S. DEPT. OF AGRICULTURE

1958. A summary of pertinent information

follows.

A helicopter needs no runway and can fly better in low visibility than light fixed-wing aircraft,

but it is more expensive.

Drift can be reduced by: (a) flying in calm

weather, (b) using low-volatile chemicals, (c)

using nozzles with large openings, (d) using water

or emulsions instead of pure oils, and (e) using

low pressures. A positive shutoff valve for each

nozzle will avoid damage from dribble.

Tanks.—Tanks are made of stainless steel, aluminum, galvanized iron, or molded plastic. Removable tank liners of synthetic rubber or plastic

shorten cleaning time and avoid contamination

when different chemicals are used. Tanks should

have large filler necks to eliminate need for a funnel and to facilitate cleaning. Use a removable

fine-mesh screen to catch sediment.

Pwnps,—Centrifugal pumps handle all kinds of

spray chemicals with least wear, but they push

the liquid in one direction only. They must be

mounted below the tank or some priming arrangement must be provided. Turbine types develop

higher pressures and move the spray in either

direction, but they have to be mounted lower than

the tank or be primed by hand.

Gravity feeds are satisfactory for herbicides

applied as coarse sprays or atomized by devices

other than standard nozzles. The pressure and

rate of flow decrease as the tank is emptied.

Pump materials must be rust resistant. Operate the pump from wind-driven propellers, hydraulic motors, electric motors, or the accessory

drive pad of the engine.

Pipes^ -ßttings^ and valves.—Pipes are made of

aluminum, stainless steel, or plastic. Hoses must

be resistant to aromatic fuels; fittings should be

durai or brass-flare type. Main-line valves should

be quick closing ; nozzles require nondribble shutoff valves.

Dusters and Spreaders

The use of dry materials, especially granular

formulations, instead of sprays is increasing.

Where water is not readily available, dusts are

substituted for sprays and applied with various

kinds of dusters from hand-operated to powerdriven machines. Dusters are simple to operate,

can be filled rapidly, and travel at faster speeds

than sprayers, but drift is a serious problem and

application of herbicidal dusts is prohibited by

law in some States.

Granular products are more practical than

dusts in most situations. Application is made by

hand, with broadcast seedsowers, with fertilizer

spreaders both small and tractor-drawn, or with

air-gun applicators. A typical hand spreader has

a rotating plate powered by a handcrank for

spreading the granules. It is carried by a shoulder sling strap, weighs 6 pounds, has a capacity

of 25 pounds, and is adjustable for various rates.

The rotary type of spreader handles heavy formulations effectively, but it is not so satisfactory

for formulations based on lighter materials such

as vermiculite.

Granular herbicides such as fenuron are applied

to brush by hand. Typical equipment consists of

a 10-quart pail and plastic spoon for each member of a crew and a 2-ton crawler tractor that

pulls a "scoot" (a sled-type carrier with steel

runners 6 inches wide and 24 inches clearance)

equipped with a 71/2- x 4-foot box in which to

haul bags of chemical. The tractor and "scoot"

are driven along the highway, the crew (10 men)

spread out across 70 feet and, as they walk, throw

a teaspoon of fenuron beside each brush cluster.

Where brush is thick, the crew uses the grid system throwing a teaspoon of chemical every 3 feet.

Applicators for Soil Fumigants

Applications of soil fumigants are made with

sprinkling cans, spreaders, hose proportioners,

soil injectors, and inexpensive applicators that

puncture the can of such fumigants as methyl

bromide and gasket the openings. Saran tubing,

evaporating pans, and a gasproof cover are necessary for those chemicals requiring cover. Applicators and other equipment are available from

distributors and dealers.

REQUIREMENTS FOR DIFFERENT TYPES

OF SPRAYS

Oils

All hose connections should be made of neoprene-type rubber. The tank need not be heavy

walled or equipped to operate under pressure.

The pump should be milled with very close tolerances ; it should not require lubrication. Pumps

that depend upon packing and repacking to prevent leakage are not satisfactory for application

of oil.

Emulsions

The pump described for oils is satisfactory for

emulsions. Internal rotary gear pumps, diaphragm, piston, and nylon-roller types are adaptable to oil-water emulsions for spraying ditchbank weeds.

Suspensions

For small areas, use lawn sprinkling cans or

knapsack sprayers. Keep spray mixture well agitated. With knapsack sprayers, use either conetype or fan-type nozzles. Often small booms with
HERBICIDE MANUAL 29

two to four nozzles spaced 20 inches apart are

useful. Skips or unnecessary overlapping can be

avoided by marking off small areas to be covered

at a time.

For large areas, use power equipment. Agitate

the spray mixture continuously so that the chemical does not settle out. Mechanical agitation is

usually adequate, but it is ineffectual if the power

unit is idled or operated at reduced speeds. Check

the effectiveness of the agitation by watching for

any powder left in the corners of the empty tank.

Effective suspension of water-dispersible powders

can be obtained with hydraulic agitation provided

from bypassed spray materials if the pump has

sufficient capacity.

To construct a jet agitator, install a pipe to the

output side of the pump and extend it to and

along the bottom of the tank to reduce foaming.

One pint of kerosene per 100 gallons spray is an

effective antifoaming agent. Fit the pipe with

sufficient jet-agitator nozzles or drill holes in the

pipe to maintain turbulence. Recirculate the solution through this pipe at about 10 percent of

the tank capacity per minute. Use no finer than

a 50-mesh screen or strainer when powders are

used.

Gear pumps wear out quickly when used for

suspensions of wettable powders. A piston pump,

driven by a separate engme or a diaphragm pump,

is more dependable. The most portable units use

a roller pump. Where tractors or trucks with

power takeoff are to be used, a good roller pump

or diaphragm pump is satisfactory.

Pumps for power-takeoff mounting deliver volumes roughly in proportion to the speed of the

shaft. Standard maximum power-takeoff speed

is about 540 r.p.m. If the speed of the powertakeoff shaft is not maintained near maximum,

pump volume drops off. Since large pump capacities are necessary if the volume for both adequate

spraying and agitation is to be maintained, it is

important to spray with the vehicle throttle set

as near maximum as possible. If the pump does

not have enough capacity to supply both the agitator and the desired number of nozzles, reduce

the ground speed of the vehicle by changing to

a lower gear and use smaller nozzles demanding

less volume.

Maintain a pressure range of 30 to 60 pounds

when a boom attachment is used. For hand-operated spray guns with larger nozzles, increase the

pressure. Since some small pumps have maximum outputs of 4 to 5 gallons per minute, it is

impossible for them to recirculate 10 percent of

a 55-gallon tank per minute and furnish additional capacit;!p^ for spraying. Use a pump with

capacity sufficient to furnish 4 to 5 gallons per

minute to the boom in addition to the volume

needed for the agitator if hydraulic agitation is

to be used.

A spray boom mounted on a tractor or some

other vehicle provides one of the most accurate

and rapid methods of application. A large area

can be covered quickly, and the spray equipment

can be calibrated accurately. In booms with large

diameters, the spray liquid does not flow so rapidly as in small-diameter booms and the powder

may come out of suspension and settle in the

boom. For average equipment, use booms % to

1 inch in diameter ; the size depends on the length

of the boom, the screen, and the size of the nozzles.

For blanket spraying with nozzles at 20-inch

spacing along the boom, the tips should be about

18 inches above the ground or tops of the weeds

for 80° nozzles and 21 inches for 70° nozzles.

These nozzle heights provide for a little overlap

of the spray pattern between nozzles ; this assures

a uniform and continuous swath.

Use a 50-mesh, or coarser, filter screen for the

suction strainer and the line strainer. For the

individual nozzles, use screens with onlj slightly

smaller openings than the nozzle opening. Do

not use flannel or cloth filters.

OPERATION

To a large extent the proper adjustment and

calibration of spray equipment determine the

success of a spraying operation. Keep the nozzles clean, and keep the volume per acre constant.

Never use a metal object to clean nozzles; an old

toothbrush cleans without injuring the orifice.

The volume can be varied by changing the pressure, the speed of travel, or the nozzle size.

Regulating Volume

A change in pressure results in only small

changes in volume. To double volume, it is necessary to increase the pressure four times. The

more convenient ways to change volume are to

change the speed of travel or to change the nozzle

tip. Doubling the speed reduces volume one-half.

The amount of spray delivered by a nozzle is directly proportional to the square of the diameter

of the opening. Thus, doubling the diameter of

the opening increases the volume four times.

Charts are available from spray-equipment companies showing capacities of nozzle size in gallons

per minute at different pressures. Some charts

give gallons per acre at designated speeds.

Even after selecting the proper nozzle, calibration is necessary. Nozzle output may vary considerably from the charted capacity. Calibration

is not necessary where rates of application are

given in pounds herbicide per 100 gallons spray

and the amount applied depends on density of

foliage or stems as in bmsh spraying with handguns.
30 AGRICT'LTÜRE HANDBOOK 2G9, U.S. DEPT. OF AGRICULTURE

Regulating Droplet Size

The smaller the droplets, the longer they remain suspended in the air and the greater the

chance of drift. The lower the pressure, the

larger the average size of droplet. With a typical

flat-fan nozzle, a decrease in pressure from 60 to

20 pounds per square inch can double the size of

the average droplet. It can also decrease by four

or five times the number of fine droplets.

To reduce the drift hazard : Never use less than

10 gallons per acre. Use 20 to 30 pounds' pressure

for broad-leaved weeds. Keep nozzles as close to

the top of vegetation or the ground as possible

while maintaining a complete coverage within the

swath. The boom may be lowered by rotating its

axis so that nozzles spray backward or forward

at an angle onto the foliage rather than straight

down. A high ground speed allows use of larger

nozzles for a given volume per acre. A high

ground speed plus high gallonage plus low pressure permits the use of nozzles with large openings ; hence, the droplets will be coarser and there

will be less drift. Use a flooding type of nozzle if

susceptible plants are nearby. Never increase output of the sprayer by raising the pressure ; change

to a larger size nozzle. Use smoke trails to determine wind direction.

Calibration of Equipment

Both hand and power equipment require calibration for the conditions under which they are

to be used. The calibration by the manufacturer

is made in the laboratory or factory and may not

apply to field conditions. Furthermore, the delivery of spray changes as the machine becomes

older, because parts become worn and strainers

and screens become partially clogged.

Hand Equipment

The volume of spraj^ per square rod or per

1,000 square feet in which the chemical can be

applied depends on the size of the nozzle and the

speed at which the operator walks. To calibrate

the sprayer, measure out a plot 1 square rod or

1,000 square feet in area. Spray the plot with

water in the equipment to be used and at the

normal walking rate of the operator. Measure

the water used. Convenient volumes for calculations are 1 pint per square rod (20 gallons per

acre), or 1 quart per square rod (40 gallons per

acre), or 2 quarts per 1,000 square feet (22 gallons per acre). The amount of chemical recommended for treatment is then mixed or dissolved

in the volume of liquid thus determined.

Power Sprayers—Boom Type

Before proceeding to calibrate a sprayer you

should do the following : Run water through the

sprayer to see that all nozzles are clean. Check

to see if they discharge at a uniform rate by running water through them at uniform pressure

and catching the discharge from each nozzle in

a separate container such as a calibrated nursing

or baby bottle. If the discharge varies widely,

replace nozzle tips.

Determine the amount of herbicide to put in

the tank by one of the following methods.

1. Determine the amount of liquid a sprayer

applies per acre as follows:

a. Start with a tank filled to the brim with

clean water. Adjust the pressure as you will

use it in the field.

b. Drive exactly one-eighth mile (40 rods,

or 660 ft.) in a field or along a road, ditchbank, or other area to be sprayed at the speed

3^ou will use when spraying—usually 3 to 5

miles an hour. Measure from where the

spray begins, not where the tractor started.

Mark the notch in which the throttle is set

and keep it there when spraying.

c. Shut off the spray, return to the original

filling position on level ground, and refill the

tank. Measure the amount of liquid required.

d. Calculate the application rate as follows:

Number of quarts used v 16.5 ,, .^^^ ^— ^__^b___^=gallons per acre width of spray swath, in feet

Example: If 6 quarts of water were used in

one-eighth mile and the spray width is 20 feet,

multiply 6 by 16.5 and divide by 20. The result

is 4.95, or about 5 gallons per acre.

6xi6.n

20

99

20^ = 4.95 gal. per acre

Divide the number of gallons the tank holds by

the number of gallons your sprayer applies per

acre. This gives you the number of acres one filling will spray. Multiply the number of acres one

tankful will spray by the amount of herbicide to

be used per acre. This gives the amount of herbicide to be used for each tankful.

Example : If the tank holds 55 gallons and the

sprayer applies 5 gallons per acre, one tankful

will spray 11 acres (55 divided by 5). If 1 pint

of spray material is required per acre, 11 pints

would be required for each tankful.

2. Catch the discharge from one nozzle in a

pint jar as the sprayer is being operated at the

speed and pressure that it will be used for spraying. Measure the distance, in feet, traveled while

collecting 1 pint. Then determine the rate of

application per acre from table 3.
HERBICIDE MANUAL 31

TABLE 3.—Calibration of sprayer by collecting the

discharge from 1 nozzle

Distance traveled

Gallons to be applied per acre when

discharge equals 1 pint and nozzles

are spaced at intervals of—

20

inches

18

inches

15

inches

12

inches

Feet

40

Gallons

82

65

54

47

41

36

33

30

27

25

23

22

20

18

17

15

14

13

12

11

5

Gallons

91

73

60

52

45

40

36

33

30

28

26

24

22

20

18

16

15

14

13

12

6

Gallons

109

87

73

62

55

49

44

40

37

34

31

29

28

24

22

20

18

17

16

15

7

Gallons

136

50 110

60 91

70 80

80 68

90 62

100 55

110 50

120 46

130 42

140 39

150 36

160 34

180 31

200 28

220 25

240 23

260 21

280 20

300 18

400 9

Example : If it takes 120 feet to collect 1 pint

of spray and the nozzle spacing on the boom is

20 inches, 27 gallons per acre would be required

(tables).

3. A variation of method 2 is to measure the

time required to collect nozzle discharge. Partially fill the tank with water, turn on the

sprayer and set to the desired pressure.

Catch the total amount of spray discharged in

a given number of minutes. Divide the number

of gallons by the number of minutes. This equals

the output in gallons per minute. It may be more

convenient to weigh than to measure the water

collected. A gallon of water weighs 8.34 pounds.

Calculate the speed of travel as follows :

495 X gallons per minute _=miles per honr

gallons per acre X spray width, in feet

Example : The nozzle output is 2 gallons per

minute, the volume of application desired is 50

gallons per acre, and the spray width is 3 feet.

i?52^=6.6 or 7 miles per hour

50x3

If the calculated speed of travel is not practical,

adjust the pressure, and calculate again.

Power Sprayers—Boomless Type

Calculated application data rather than calibration are used for boomless sprayers. These data

are available from the manufacturers of nozzles.

Aerial Sprayers

Determine the flow rate in gallons per minute

as follows :

Put a measured amount of spray in the tank

or fill the tank to a definite level. Instruct the

pilot to turn on the spray for a timed interval

(30 or 60 seconds) while flying level and straight

at the speed to be used for spraying. When the

plane lands, drain and measure the liquid remaining in the tank or, with the plane in the location

where the tank was filled, measure the amount required to refill the tank to the same level. Compute the flow rate in gallons per minute. Compute the flow rate required as follows :

SWD

F =495

S =speed of plane in m.p.h.

"^rrwidth of effective swath (not total swath),

in feet

D = dosage to be applied in gallons per acre

F =flow rate, in gallons per minute

60X43,560 _

'"^;28Ô ^^^

Example: S=^0 m.p.h.; Tf=40 ft.; Z>=2 gallons per acre.

80x40x2_i9Q gal. spray required per minute.

495

CLEANING AND PREPARATION FOR STORAGE

Cleaning After Each Use

All spraying equipment should be cleaned after

use. If the chemical is soluble in water, a thorough flushing and rinsing with water is sufficient.

Equipment that has been used for phenoxy herbicides such as 2,4-D, 2,4,5-T, silvex, erbon, or

MCPA is very difficult to clean. Use one of the

following methods for hand sprayers or field

equipment.

1. Eemove nozzles and scrub with kerosene.

2. Ammonia rinse.

(a) Add a box of nonsudsing detergent

to 30 to 40 gallons of water, run

through pump, and bypass for 5

minutes and then out through the

boom.

(b) Partly fill tank with a solution of

1-percent to 2-percent household

ammonia (1 to 2 quarts in 25 gallons

water, or 2 teaspoons per quart

water).
32 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

(c) Leave this solution in the sprayer

(including hoses and boom) overnight.

(d) Kinse thoroughly with clean water.

3. Charcoal rinse.

(a) Use at least one-third of a tank of

water. For each 10 gallons of water

add one-quarter pound of activated

charcoal and one-eighth to one-quarter pound of laundry detergent.

Agitate this mixture vigorously to

distribute the charcoal through the

water.

(b) Wash the equipment for 2 minutes

by swirling the liquid aroimd so that

it reaches all parts of the tank.

Pump some of the liquid through

the hose and nozzles.

(c) Drain the tank and rinse the equipment with clean water.

Preparation for Storage

Scrub the sprayer with a stiff bristle brush.

Coat all iron parts exposed to the chemical with

a rust inhibitor or light oil. Remove nozzles,

take apart, clean, and store in light oil—before

using the next year, wash in kerosene or gasoline

to remove oil.

Fill pump with a rust preventive.

Remove caps from the ends of booms and stand

booms on end to remove sediment. Remove, clean,

and reassemble filters.

If the sprayer is powered with a gas engine,

drain fuel tank and carburetor, and pour a tablespoon of engine oil through a spark plug hole.

Turn motor over by hand to distribute oil on

cylinder walls.

If the sprayer is to be stored outside, remove

rubber hoses and keep in a cool dark place.

Thoroughly clean dusters and spreaders before

storage.

APPLICATION OF HERBICIDES

In the following pages, rates of application are

given in minimum and maximum amounts. This

spread in amounts to apply is necessary to take

care of differences in the response of species, the

stage of growth when treatment is made, the

period of residual toxicity desired, the amount

and distribution of rainfall, soil textures and composition, and other environmental conditions. In

general, the proper rate for a specific situation

can be determined from table 4. Extremes are

given; rates for intermediate conditions can be

approximated.

Many rates are given in units of chemical per

1,000 square feet, per square rod, or per acre. It

is not necessary, however, to measure the area

to be sprayed each time an application is made.

Calibrate the sprayer at the beginning of each

season for the volume of spray delivered per

unit of area. If the amount of chemical per unit

of volume is known, the rate per unit of area is

easily determined (p. 22).

Volume of spray needed varies with density of

foliage. For applications to the soil, it can be as

low as the sprayer can distribute uniformly, except that it should be increased where trash or

vegetation is present.

The lists of hard-to-kill weeds for each herbicide are not complete; they include only those

whose response to a herbicide has been determined. Since available information varies widely

among chemicals and among regions, the longer

list for one chemical compared with others does

not necessarily indicate that it is less generally

effective. It may result from wider investigation

of plant response to this chemical.

TABLE 4.—Sitv/itions where light and heavy rates

of herbicides are needed

Light rates Heavy rates

HERBACEOUS PLANTS

Susceptible species

Annuals

Seedlings

Perennials in bud

Shallow-rooted

Tolerant species

Perennials

Annuals and biennials in flower

Established perennials—^flower

to maturity

Deep-rooted

V^OODY PLANTS

Susceptible species

Foliage applications

when plants are in

fuU leaf

Actively growing

Tolerant species

Foliage applications before and

after full leaf

Dormant

Short period

Arid regions

RESIDUAL TOXICITY

Several years

Humid regions

SOIL TYPE

Low in organic-matter High in organic-matter content

content

Low in clay content High in clay content

Well drained Poorly drained

ROOT-ABSORBED CHEMICAL

Bare soil Heavy trash

FOLIAR-ABSORBED CHEMICAL

Light growth Heavy growth
HERBICIDE MANUAL 33

ALL VEGETATION

There is no one herbicide available that meets

all requirements for complete control of vegetation. At practical rates of application, even the

soil sterilants do not always kill all vegetation.

There are two major reasons. First, there are

certain weed species that are resistant to each of

the soil sterilants listed in this handbook, and,

second, these herbicides do not behave equally

well under all environmental conditions. To be

effective, a soil sterilant must be soluble enough

to be carried into the root zone by soil water but

also it must remain long enough for a lethal dose

to be absorbed by the plant. Aside from the relative solubility of the chemical, its movement and

persistence in the soil are influenced by (1) the

rainfall pattern of the area, (2) the physical and

chemical properties of the soil, such as texture,

structure, and pH, and (3) the micro-organisms

in the soil that are able to deactivate the chemical.

Failure to get expected control may result from

an incomplete distribution of the herbicide in the

soil or from amounts in the soil solution inadequate to effect a kill. A chemical of low solubility may be adsorbed in the upper soil layer and

not reach deeper roots. This may happen in soils

with poor underdrainage, in dry regions, or

when the treatment was made at the wrong time.

A soluble chemical may leach out of the soil before plant roots absorb a lethal dose. This occurs

most commonly in sandy soils with excessive underdrainage and where rainfall is high, in seasons of heavy showers, and under irrigation. It

may also result from improper timing of the

treatment. When hard-to-kill species are a problem or where environmental factors reduce the

activity of a chemical, (1) increase the rate of

application, (2) use a mixture of chemicals, or

(3) repeat the treatment.

The rates of application and the optimum time

for treatment also vary with the soil, the rainfall, and the weed species to be controlled. In

most areas, it is better to make repeated annual

applications of soil sterilants at relatively light

rates than to rely on a single heavy treatment.

Such a maintenance dosage results in a smaller

annual expenditure than a "one shot" method and

keeps chemicals in the surface soil where they

can kill weed seeds coming in from outside. Nongrass species are usually the first vegetation to

re-infest sterilized areas. Kelatively inexpensive

treatments with esters of 2,4-D at 1 pound per

acre will maintain areas free of vegetation for

several additional years. Where species difficult

to control are present, spot treat such plants by

hand rather than use a general spray treatment

at rates high enough to kill the tolerant weeds.

On areas where the perennial weeds are susceptible to the phenoxy herbicides, it is economical

to use a relatively insoluble soil sterilant such as

simazine or diuron to control annual weeds and

2,4-D, MCPA, or silvex to kill the perennials.

The soil sterilant is applied preemergence to moist

soil at 4 pounds in 100 gallons water per acre.

The phenoxy compound is applied tp perennials

at 1 pound per acre when they are in full leaf and

growing rapidly to induce the maximum translocation to their roots. For this method to be successful, the soil sterilant must remain near the

surface and there must be enough rain to activate

it. Heavy rain will leach the herbicide and

shorten the period of control. Incorporation of

the chemical with the soil helps activate it in

dry seasons, but this does not suDstitute for rain.

The application of herbicides useful on areas

where bare ground is necessary for accessibility,

visibility, and prevention of fire is discussed under two groupings: (1) relatively permanent soil

sterilants and (2) foliage-applied nonselective

herbicides.

Relatively Permanent Soil Sterilants

Soil sterilants, when present in the soil, prevent

the growth of green plants. The soil may or may

not be sterile. These chemicals are used in storage areas, lumberyards, and parking lots; on tennis courts and racetracks; under j)ipelines and

transformer cages; under guardrails and surrounding signposts on highways and lights on

runways; near fire hydrants, trestles, and bridges;

on public utility rights-of-way ; on gravel blanket

areas; around buildings, grain elevators, utility

poles, and tank farms; along fence rows; for firebreaks; and in similar areas where any plant

growth is undesirable. There are two major

problems in maintaining bare ground: (1) no

herbicide kills all species at reasonable rates of

application and (2) re-infestation results from

weed seeds in the soil after the herbicide has been

leached below the surface. Meet these problems

by using a combination of chemicals effective

against the weed species to be killed and by repeated applications of the proper herbicide to

kill seedlings.

Single-Chemical Soil Sterilants

Single-chemical herbicides are satisfactory

where the weed population is restricted to a few

susceptible species or where hard-to-kill species

can be controlled easily and economically by a

second treatment. For example, dandelions or

plantain that are tolerant to monuron and diuron

can be killed with an application of 2,4-D.

Arsenicals

Rates of application vary widely, depending on

soil texture, rainfall, and species of plant. For

general application, where no adjustment for
34 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

these factors is made, use I4I/2 pounds AS2O3 per

1,000 square feet, 4 pounds per square rod, or 640

pounds per acre and repeat as necessary. For

light soils, apply 8 to 15 pounds per 1,000 square

feet, 21/4 to 4 pounds per square rod, or 360 to

640 pounds per acre; for loam soils, 15 to 22

pounds per 1,000 square feet, 4 to 6 pounds per

square rod, or 640 to 960 pounds per acre; and

for clay soils, 28 to 44 pounds per 1,000 square

feet, 71/^ to 12 pounds per square rod, or 1,200 to

1,920 pounds per acre. Use the heavier rates on

all soil types for seashore saltgrass and other

grasses. The higher rates also provide longer

periods of sterility in dry regions. For adobe and

red soils derived from basic igneous rocks, double

the rate for each soil texture.

Caution.—Inorganic arsenicals are very poisonous and caustic. Avoid contact with the skin and

eyes, contamination of clothes, and inhaling spray

fumes. For skin protection, use an arsenic-resistant cream such as Kerodex No. 71 (water repellent). Sodium arsenite is dangerous to livestock

because they eat treated plants. Prevent access

to treated vegetation until the chemical has been

washed from the plants.

If the chemical is swallowed, induce vomiting.

When vomit fluid is clear take raw eggs, milk,

limewater, flour and water, or sweet oil to absorb

the poison and soothe irritated membranes. If

the chemical is spilled on the skin, wash immediately and rinse with boric acid.

Water with more than 0.05 p,p.m. (parts per

million) is not safe for drinking. Wait 2 days

after treating water before using it to water

lawns, for bathing, to water livestock, or for

other similar purposes. Keep pets away for 2

days. There are no reports of widespread damage to birds from arsenicals used as soil sterilants.

Benzole acid compounds

Apply 20 to 30 pounds, acid equivalent, in 50

to 100 gallons water per acre for broad-leaved

weeds. Use the heavier rates when weeds are in

full leaf and for longer control. Wet the foliage

thoroughly. For spot treatment, dissolve 2 oz.,

acid equivalent, per gallon water and apply 31/2

gallons per 1,000 square feet, 1 gallon per square

rod, or 20 pounds per acre.

Among the broad-leaved weeds camels-thorn;

milkweed, climbing; povertyweed; rubberweed,

Colorado; smartweed, swamp; and sweetfern are

hard to kill.

Caution.—Do not use on walks, driveways, tennis courts or other areas where desirable vegetation can be affected by leaching or washing. Do

not drain or flush out equipment used for applying this chemical near desirable plants or on areas

where roots may have extended below the surface

or where the chemical may be washed into contact with the roots. Do not apply to areas where

nearby fields are to be used for susceptible crops.

Clean equipment thoroughly after use. Avoid

contact with skin, eyes, and clothing ; it is a mild

skin irritant.

Erbon

Apply 3 to 4 pounds erbon per 1,000 square

feet, 34 to 1 pound per square rod, or 120 to 160

pounds per acre. Use the higher rates in areas

of high rainfall. Mix with water in proportion

of 1 part of a 4-poimd formulation to 6 parts

water, and cover vegetation thoroughly. For bare

ground use enough volume for uniform distribution. Apply in late spring or early summer in

northern areas and in early to midwinter in California and other areas of medium to light rainfall. For spot treatment, mix 1 part of a 4-pound

formulation with 4 parts water, and wet all vegetation and exposed bare ground. Spray an extra

5 feet beyond the weed patches.

Hard-to-kill weeds are: cattail; heliotrope,

wild; horsetail, field; johnsongrass; sida, alkali;

milkweed, climbing; quackgrass; saltgrass, seashore; and sedge.

Caution.—Erbon is irritating to the skin and

eyes. If contact is made, wash skin thoroughly

with water and soap or wash eyes with water for

15 minutes. Prevent drift to susceptible plants.

Fenac

Early preemergence treatments are more practical than postemergence since fenac is slow to act.

It is readily adsorbed in heavy soils and those

high in organic matter; hence, larger rates are

required than for light sandy soils.

Apply 4 to 6 pounds, acid equivalent, per acre

for puncturevine or Eussian-thistle. In areas of

more than 10 inches of rainfall, apply to puncturevine in late winter or early spring. In drier

areas, apply in the fall. In areas of seasonal

rainfall, apply in late fall or early winter for

Kussian-thistle before it germinates. In other

areas apply in the spring before germination.

Apply 18 to 20 pounds per acre for field bindweed, leafy spurge, Russian knapweed, and Canada thistle. Apply any time during the growing

season, preferably before the rainy season. Thoroughly wet the foliage and soil around the weeds.

If topgrowth is heavv, remove before application

or disk it into the soil.

Apply 15 pounds per acre for annuals and burfranseria and alkali sida (perennial broad-leaved

weeds). Apply preemergence in early spring for

annuals but not to frozen ground. Apply in fall

or spring for perennials to permit leaching of

chemical to the roots.

Caution.—Do not swallow. Wash thoroughly

with soap and water if chemical is spilled on the

skin.
HERBICIDE MANUAL 35

Monuron and diuron

In areas of low rainfall, apply monuron in late

fall or early spring but not to frozen ground. In

areas of high rainfall, apply in late spring or

early summer. Apply diuron in fall or early

spring only in areas of high rainfall, especially

on sandy soils or when heavy rains can be expected to follow application. Apply at or below

the waterline of ditches and ponds. If a quick

topkill of weeds in addition to soil sterilization is

wanted, use weed oil as the carrier or an oil-water

emulsion. Add 8 pounds monuron or diuron to

100 gallons aromatic weed oil and apply per acre.

If an emulsion is used, add 1/2 pound calcium

caseinate conditioner to each 100 gallons spray.

Add the monuron or diuron and the conditioner

to the tank when the water is just above the agitator, and add the oil before the tank is over onethird full. Good agitation is essential.

Rates vary from 20 to 80 pounds, active ingredient, per acre. Water is the carrier most frequently used. Remove topgrowth before treatment if it is heavy; translocation from leaves to

roots does not occur. Use only enough water to

make a uniform application. The heavier rates

of chemical increase the rapidity and depth of

penetration and lengthen the period of residual

effects. Use them on the heavier soils, organic

soils, and for the control of perennials. Increase

the effectiveness of monuron alone by adding sodium chlorate—8 pounds monuron to 100 pounds

chlorate; increase the effectiveness of diuron by

adding 2,3,6-TBA—8 pounds 2,3,6-TBA to 25

pounds diuron. For spot treatment, use 11/2 to

2 pounds per 1,000 square feet, one-half pound

per square rod, or 65 to 87 pounds per acre; for

small areas, use 5 cups per 1,000 square feet or

50 pounds per acre and apply in at least 2 gallons

water. Stir frequently. Results may be poor on

soils impregnated with wood charcoal as around

lumber mills.

Hard-to-kill weeds, requiring 30 to 40 pounds

per acre, are: bermudagrass; bindweed, field;

dallisgrass; houndstongue ; ragwort, golden ; saltgrass, seashore; seamyrtle; smartweed, water;

sowthistle, perennial ; tansy-ragwort; thistle, Canada; and whitetop.

For the broad-leaved perennials, include 2,3,6-

TBA at 20 to 30 pounds, acid equivalent, per

acre.

Caution.—If spread on the surface and exposed

to intense and extended sunlight, these chemicals

may be decomposed before they are carried into

the soil. Under such conditions work them into

the surface soil.

Do not use on walks, driveways, tennis courts,

and other areas where desirable vegetation can be

affected by leaching or washing. Monuron and

diuron do not move far laterally in the soil, but

they may be washed down slopes to kill vegetation below and they leach deeply enough to reach

the roots of trees, shrubs, and other deep-rooted

plants growing under the treated area. Apply a

light coating of road oil to hold the herbicide in

place. Fill treated excavations with a layer of

crushed rock to reduce erosion. Do not drain or

flush out equipment used for applying these

chemicals near desirable plants or on areas where

roots may have extended below the surface or

where the chemicals may be washed into contact

with the roots. Both monuron and diuron can

irritate eyes, nose, throat, and skin.

MonuronTCA

Apply dry at 150 to 200 pounds per acre of

product containing 22 percent monuronTCA for

most weeds; 300 pounds for hard-to-kill species.

Apply as a spray at 21 to 42 pounds monuronTCA per acre for most weeds; 42 to 66 pounds

for hard-to-kill species. Dilute with enough kerosene, fuel oil, or aromatic weed oil to cover well.

The amount depends on density of vegetation—

75 to 150 gallons per acre. The carrier can also

be water. Mix in the proportion of 1 gallon of

3-pound concentrate in 19 gallons of water. Add

the liquid formulation to the water with constant

agitation, and apply within a few hours after

mixing.

For spot treatment, use one-quarter to one-half

cup liquid in 2i/^ to 5 gallons oil.

Apply just before or just after growth begins

in the spring. Later applications are more slowly

effective. Mow tall plants before treatment. In

semiarid areas, apply before rainy season ends.

Both the dry and spray applications are absorbed

through roots and must be carried to the root

zone by rain. Apply the liquid formulation in

the fall for deep-rooted perennials.

Species that require the heavier rates are:

bracken; carrot, wild; cocklebur, common; dock,

curly; houndstongue; johnsongrass; mugwort;

quackgrass; ragwort, golden; sowthistle, perennial; spurge, leafy; thistle, Canada; vaseygrass;

and whitetop.

Caution,—In areas south and east of region 1

(fig. 1, p. 42) toxicity is short unless high rates

are used.

Do not drain or flush equipment near desirable

plants or on areas where roots of such plants

may extend. Prevent drift. Clean application

equipment with water and a detergent to prevent

corrosion. The herbicide is harmful if swallowed

and is irritating to skin and eyes.

Simazine and atrazine

Apply as a suspension in water or dry in granules. Apply before or during emergence of weeds

at 3 to 4 ounces per 1,000 square feet, 1 ounce per

square rod, or 10 pounds per acre, active ingredient, for 1-year control, 15 to 25 pounds per acre
36 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

for longer residual effects. Eemove vegetation

before treatment. Use the higher rates for clay

soils or soils high in organic matter. If spraying

is delayed, mix sodium chlorate with simazine at

the rate of 2l^ pounds per 1,000 square feet, 10

ounces per square rod, or 100 pounds per acre.

Weeds requiring the heavier rates of simazine are: bermudagrass; bullnettle; canarygrass.

Reed; euonymus; honeysuckle; horsenettle, Carolina; juniper; maple; mockorange; panicum; St.-

Johns-wort, spotted; spikerush, creeping; and

willow.

Those requiring heavier rates of atrazine are:

horsenettle, Carolina; nutgrass, yellow; panicum;

and St.-Johns-wort, spotted.

Add the chemical to the spray tank during or

after filling with the required amount of water

(20 to 40 gallons per acre). Provide adequate

agitation to keep the chemical in suspension.

Use Tee-Jet 8002, 8003, or 8004 fan-type or similar nozzles with openings of equal or larger size.

Use screens no finer than 60 mesh. Set pressure

at 20 to 40 pounds per square inch.

Caution,—^Use the same precautions against

washing and leaching as for monuron and diuron.

Prevent drift of atrazine.

Sodium chlorate

In dry climates, apply in the fall so that winter

rains may carry the chemical into the soil. In

areas of heavy winter rains, apply dry in late

winter. In humid areas, apply in the fall for

perennial weed control and in the spring for annuals. Avoid applications just before a long

rainy period. Rates vary widely to meet differences in soil texture and fertility, rainfall, and

response of weed species. An average application

is 11 pounds per 1,000 square feet, 3 pounds per

square rod, or 480 pounds per acre. In semiarid

regions, rates vary from 11 to 22 pounds and in

liumid areas or on soils high in nitrates from 22

to 44 pounds per 1,000 square feet. Use the

lighter rates for susceptible species under optimum conditions and heavy applications for tolerant species and unfavorable conditions. For a

quick kill of topgrowth, apply sodium chlorate in

100 to 500 gallons water per acre; otherwise, apply dry, since the fire hazard is less. If used in

mixtures that reduce the fire hazard, base rates on

the amount of sodium chlorate contained.

Hard-to-kill species are: blackberry; dock,

curly; horsetail, field; kikuyugrass; morningglory; saltgrass, seashore; and whitetop.

Caution,—Store and handle only in metal containers. Store away from wooden buildings and

out of reach of children and livestock. Clothing

or other organic material on which sodium chlorate has dried is extremely flammable. Do not

smoke when handling or spraying. Do not spray

around wooden buildings or on other flammable

organic matter near buildings. Do not drive or

walk through treated areas, and keep livestock

away until a rain has washed off the chlorate.

Wear rubber boots when spraying. Remove clothing wet with spray and wash before using again.

Thoroughly drain and flush equipment with

water. The toxicity is quite low in usual concentrations, but it is hazardous to stock in large

doses. It is toxic to fish.

Trichloroacetic add

(WSA designation, TCA)

Apply to soil when rain can be expected to

carry it to plant roots. If there is considerable

vegetation or trash on the area, remove it or disk

it in before treatment. Rate of application depends on whether or not tillage can be combined

with treatment. Where tillage is impossible, use

1.8 to 2.75 pounds per 1,000 square feet, one-half

to three-quarter pound per square rod, or 80 to

100 pounds per acre, acid equivalent. If bermudagrass, cutgrass, tall larkspur, panicum, or

paragrass are present, remove topgrowth, increase the rate to 125 to 150 pounds per acre, and

apply preemergence. Where tillage is possible,

30 to 40 pounds are adequate. For spot treatment, dissolve 1 pound in 1 gallon water; wet all

foliage and exposed roots thoroughly. Uniform

distribution of TCA spray is important. Use

enough water for uniform distribution on bare

ground and up to 300 gallons per acre where trash

or vegetation is heavy.

Caution,—The solid fomáulations or strong

aqueous solutions of sodium TCA (50 percent or

more) may cause bums if skin is exposed to them

for an hour or more and they may be painful to

the eyes. Wash affected parts with water if contact is made. Flush equipment with water immediately after use.

Soil Sterilant Mixtures

For some situations, mixtures of two or more

chenaicals are more effective than single-chemical

herbicides. Proprietary mixtures are combinations of chemicals that (1) provide a quick knockdown of vegetation plus a residual toxicity in the

soil, (2) consist of one best adapted to kill broadleaved weeds plus one best adapted for grassy

weeds, or (3) consist of a dangerous fire hazard

plus a fire deterrent.

Caution.—Observe the precautions as given for

each chemical in the mixture.

Borate-monuroa

(WSA designation, BMM)

Apply dry in fall, winter, or early spring.

Make summer applications only in areas where

there is sufficient rain to carry the herbicide to
HERBICIDE MANUAL 37

the plant roots. Apply 5 to 10 pounds product

per 1,000 square feet, V^ to 3 pounds per square

rod, or 220 to 440 pounds per acre to annuals and

up to 900 pounds per acre to perennials. In the

Eastern States, use up to 1,700 pounds per acre.

Weeds requiring the heavier rates are: bermudagrass; bracken; dandelion; golden-aster,

false; horsetail, field; horseweed, marestail;

knapweed, Eussian; nutgrass, purple; panicum;

sedge; spurge, upright; thistle, Canada; and

vaseygrass.

Borate-2,4-D

(WSA designation, BDM)

Apply dry to control broad-leaved plants only.

Apply 10 pounds product per 1,000 square feet,

2.75 pounds per square rod, or 440 potinds per

acre to annuals in the spring when they are

emerging. Apply up to 30 pounds per 1,000

square feet to perennials in the fall when nearing

maturity. Do not use in late spring and summer

unless there is sufficient rain to carry the chemical to the root zone.

Bracken and Russian knapweed are hard to kill.

Chlorate-borate

(WSA designation, CBM)

Apply as a spray for quick topkill. For annuals, use 10 pounds product in 5 gallons water

per 1,000 square feet, 2.75 pounds per square rod,

or 440 pounds per acre ; thoroughly wet the foliage. For deep-rooted perennials, use 20 to 40

pounds dry product per 1,000 square feet, 5i/¿ to

11 pounds per square rod, or 870 to 1,740 pounds

per acre or dissolve 2 pounds product per gallon

water and use 10 to 20 gallons of the solution per

1,000 square feet. In California and similar

areas, use 1,600 to 2,000 pounds dry product per

acre. For hard-to-kill weeds, apply the heavier

of the rates given.

Bermudagrass; biadweed, field; quackgrass;

and whitetop are hard to kill.

Caution.—^Do not apply to tall vegetation or

in hot dry weather, because of the fire hazard.

Do not use on slopes where the chemical can wash

onto desirable plants. Wash clothing and equipment after application. The fire hazard from

sodium chlorate is greatly reduced in this mixture, but precautions are advisable.

Chlorate-borate-monuron

(WSA designation, CBMM)

Apply dry or as a spray at following rates of

product: annuals and shallow-rooted plants, 10

pounds per 1,000 square feet, 2.75 poimds per

square rod, or 436 pounds per acre; perennials

and deep-rooted plants, 15 pounds per 1,000

square feet; 20 pounds for hard-to-kill grasses.

Apply to annuals in the spring when they are

small and to perennials in areas of over 20 inches

rainfall. In semiarid areas, apply to perennials

in fall or early winter.

Bermudagrass; bindweed, field; dandelion;

Johnsongrass; knapweed, Russian; licorice, wild;

quackgrass; seamyrtle; spurge, upright; and

vaseygrass are hard to kill.

Caution.—Observe the same precautions as for

chlorate-borate.

Foliage-Applied Nonselective Herbicides

The foliage-applied nonselectives are used primarily to kill weeds on land later to be cropped ;

but they also are useful on land where long residuals are not required, where quick kills are

needed, and where weeds have survived or escaped treatment with a long-lasting soil sterilant.

Some of the sélectives, like the phenoxy compounds, remove broad-leaved weeds from grass

sods, while others, like dalapon, control grasses

without severe injury to most broad-leaved plants.

These herbicides are used where the killing of

vegetation for long periods is undesirable because

erosion is a problem or for esthetic reasons.

Single-Chemical Herbicides

Amitroie and amitrole-T

For annual broad-leaved weeds and annual

grasses, use a solution of 2 pounds, active ingredient, in 100 gallons water. Wet thoroughly.

For perennial broad-leaved weeds, use a solution

of 4 pounds, active ingredient, in 100 gallons

water; apply in bud to bloom stage. Wet thoroughly. When using a spray boom, apply at the

rate of 4 pounds, active ingredient, in 40 to 50

gallons water per acre. The perennial grasses are

more difficult to kill. For these use amitrole-T

at double the rates for perennial broad-leaved

weeds or use a mixture of amitroie with monuron, with simazine, with TCA, or with dalapon.

Dalapon

For temporary control of mixed broad-leaved

and grassy annuals, apply 10 pounds dalapon,

acid equivalent, plus 1 to 2 pounds low-volatile

ester of 2,4-D, acid equivalent, per acre. Increase

rates for longer control. For hard-to-kill grasses,

such as kikuyugrass, panicum, quackgrass, and

redtop, apply 30 to 50 pounds dalapon m 100 gallons water per acre with a boom sprayer or, if

using a handgun, dissolve 10 to 20 pounds dalapon in 100 gallons water and apply 200 to 400

gallons per acre and wet the foliage thoroughly.

For spot treatment, dissolve 1 pound dalapon in

5 to 20 gallons water; add one-quarter to onehalf pound detergent, such as Tide or Dreft, if

the foliage is hard to wet. Several applications

of any of these sprays are usually necessary to

maintain weed control. Apply when grasses are
38 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

leafy and growing vigorously. Do not apply

during droughts.

Most broad-leaved weeds are hard-to-kill or

resistant.

Caution.—Do not allow spray solutions to

stand more than 2 days after they are mixed. In

combination sprays with 2,4-D, do not use a solution more concentrated than 6 pounds dalapon,

acid equivalent, to 10 gallons water. Fill spray

tank at least half full of water before adding the

chemical and stir until completely dissolved. Prevent drift. Avoid contact of undiluted dalapon

«or dust with eyes, skin, or clothing. Wash affected parts with water if contact is made. Flush

equipment with water immediately after use.

Herbicide Mixtures

A mixture of amitrole with dalapon, amitrole

with other chemicals, or of dalapon and silvex

is often more effective for the complete control of

vegetation than amitrole or dalapon alone. This

is true where the plant population includes annuals and perennials, grasses and nongrasses,

herbaceous and woody plants, or species tolerant

to one of the constituents but susceptible to another. Some combinations are available as proprietary mixtures, others have been tried as homemade mixtures.

Amitrole-dalapon ; amitrole-monuron ; amitrolesimazine; amitrole-TCA

For annual grasses and perennial broad-leaved

weeds: use 4 pounds amitrole and 10 pounds

dalapon, acid equivalent, per acre (5 oz. of the

mixture per 1,000 sq. ft. or li/^ oz. per sq. rd.) ;

4 pounds amitrole and 20 pounds monuron per

acre (8.8 oz. of the mixture per 1,000 sq. ft. or

:2.4 oz. per sq. rd.) ; or 4 pounds amitrole and

10 pounds simazine per acre (5 oz. of the mixture

per 1,000 sq. ft. or 11/2 oz. per sq. rd.). For annual weeds: apply 2 pounds amitrole and 10

pounds monuron per acre (41/2 oz. of the mixture

per 1,000 sq. ft. or 1% oz. per sq. rd.) or 2 pounds

amitrole and 5 pounds simazine per acre (21/2 oz.

of the mixture per 1,000 sq. ft. or 0.7 oz. per sq.

rd.). Eates for amitrole, monuron, and simazine

are in active ingredients.

If amitrole and TCA is used, apply 5 pounds

amitrole, active ingredient, and 50 pounds TCA,

acid equivalent, per acre (ll^ lb. of the mixture

per 1,000 sq. ft. or 51/2 oz. per sq. rd.) for most

weeds. For Johnson and bermuda grasses and

for heavy stands of other grasses, double the rate

of TCA.

Time and methods of application are the same

as for the single ingredients of the mixtures.

Caution.—Eefer to precautions for handling as

follows: dalapon, p. 37; monuron, p. 35; simazine, p. 36; and TCA, p. 36.

Dalapon-silvex

For areas of mixed grasses and nongrasses, use

a liquid formulation containing 4 pounds dalapon,

acid equivalent, and one-half pound silvex, acid

equivalent, per gallon at the rate of 3 gallons in

97 gallons water. Apply in large enough volume

to wet the foliage thoroughly (200 to 300 gallons

per acre). Apply at least 6 gallons of the herbicide per acre. For spot treatment, use 1 pint of

the herbicide in 3 gallons water per 1,000 square

feet. Apply when plants are young and growing

vigorously. Ke-treat or spot treat for seasonal

control.

Quackgrass and spurge are hard to kill.

Caution.—Prevent drift. Avoid contact with

eyes, skin, and clothing.

Contact Herbicides

Contact herbicides are often more practical

than soil sterilants in areas where leaching is

rapid and where mowing or cultivation of unwanted vegetation is difficult. They are also well

adapted for spot treatment of shallow-rooted

perennials and weeds that come up through cracks

in pavement, ditch lining, or gravel drives. Contact herbicides kill only the topgrowth of herbaceous vegetation wet by the spray, so that complete coverage is essential. They usually kill

annual broad-leaved weeds, but they may not kill

the roots and underground storage organs of

perennials and they may not always kill annual

grasses. To kill grasses, the spray must creep

down the stems to the crowns. Oil sprays are

most effective for this use. Contact sprays do

not prevent reinfestation by seedlings nor do they

always prevent recovery of perennial plants from

crown or root buds. For these reasons, repeated

applications are usually required to keep an area

free from vegetation. Although some contact

herbicides kill quickly, the heavy fuel oils and

aromatic oils act slowly.

Herbicidal oils

Use sufficient volume to wet plants thoroughly

and cover to as near the ground line as possible.

For grasses, wet the plant until excess spray

creeps down the stems. Use 80 to 160 gallons oil

per acre. Maintain 60 p.s.i. at the nozzles. On

boom sprayers, space the nozzles so that the spray

fans meet just above the tops of the vegetation

and adjust height of boom to 18 inches or less

above the plants. For dense growth, provide double coverage from different angles. When spot

spraying, travel slowly and wet thoroughly. Repeat treatments where seasons are long and rainfall is high.

For oil-tolerant species, use 2,4-D on broadleaved plants or TCA or dalapon on grasses before spraying with oil.
HERBICIDE MANUAL 39

Caution.—Highly volatile oils with low flash

points ignite easily and may be explosive. All of

the oils are flammable. All hose connections

should be of neopiene-type rubber.

Dinitros

Apply sufficient volume to wet the vegetation

thoroughly, since these compounds are not translocated. The parent compounds are more effective than their salts. Add a wetting agent if

grasses are present. Apply in warm weather;

these herbicides are most toxic at temperatures

above 80° F. and at a high humidity; below 60°

F., they are not very effective.

For general weed control, use 2 to 3 pints

DNBP or DNAP in 5 to 30 gallons oil in enough

water to make 100 gallons spray. Use the lower

amounts of chemical and oil for young, succulent

growth; larger amounts for older, coarser, and

hard-to-kill species. Unless an activator has been

added, add 6 to 9 pints DNC to the same amount

of oil and water. Since these compounds kill vegetation quickly, spray a trial strip to determine

proper amounts of chemical and oil for best results.

Caution.—Keep the dinitros from contact with

eyes, skin, and clothing. Avoid breathing spray

drift; do not swallow any ; wear synthetic rubber

gloves, a respirator, and goggles ; and wash clothing before using again. Keep the oil solutions

away from heat and open flame. Dinitros are

yellow dyes that will stain sidewalks, driveways,

skin, and clothing. They are toxic to game and

fish.

If any chemical is swallowed, send for a physician, induce vomiting, and when vomit fluid is

clear, take 2 tablespoons of baking soda in a glass

of water.

Pentachiorophenol

(WSA designation, PCP)

Apply sufficient volume to wet the vegetation

thoroughly, since PCP is not translocated. The

parent compound is more effective than its salts.

Add a wetting agent if grasses are present. Apply in warm weather ; PCP is most toxic at temperatures above 80° F. and at a high humidity;

below 60° F., it is not very effective.

Caution.—Avoid breathing PCP dust, and

avoid contact with skin and clothing. Do not

swallow any. PCP is considered moderately

toxic, but experience in the tropics indicates it

is more dangerous than thought. Skin absorption

is the primary danger.

If the chemical is swallowed, send for a physician, induce vomiting, and when vomit fluid is

clear, take 2 tablespoons of baking soda in a glass

of water.

Emulsions

The following formulas are satisfactory for

broad-leaved weeds and grasses growing in sheltered locations.

1. Pentachiorophenol, 4 pounds, or DNBP, II/3

pounds

Aromatic oil, 8 gallons

Oil-soluble wetting agent, 4 pounds

Water, 92 gallons

Add the pentachiorophenol to the oil and agitate until it is all dissolved, then add the oil-soluble wetting agent and agitate until a uniform

solution is obtained. This makes a stable concentate that may be stored. To prepare the spray

solution, mix equal volumes of concentrate and

water, agitate vigorously until a stable emulsion

is formed, then add the remaining water with

agitation.

2. Dinitro concentrate, 1 quart

Diesel oil, 15 gallons

Water, 85 gallons

For old, tough weeds use :

3. Dinitro concentrate, 1 quart

Diesel oil, 40 gallons

Water, 60 gallons

For more vigorous grasses, increase the percentage of oil or decrease the volume of water.

If more oil is required, mix it with the fortified

oil in No. 3 and emulsify the entire mixture. For

the supplementary oil, use any kind with a viscosity (p. 13) not over 50 seconds. Use up to

50 percent oil if necessary. Maintain at least

100 p.s.i. at the nozzles and keep the emulsion

agitated.

WEEDS IN SPECIFIC AREAS

For precautions in handling the chemicals recommended in this section, refer to :

Amitrole-dalapon mixture, p. 38

Amitrole-TCA mixture, p. 38

Chlorate-borate mixture, p. 37

Dalapon, p. 37

Dalapon-silvex mixture, p. 38

Dinitros and PCP, p. 39

Diuron, p. 35

Erbon, p. 34

Monuron, p. 35

Monuron TCA, p. 35

TCA, p. 36

Paved Highways

Vegetation that encroaches from the edges of

asphalt pavement or grows up through cracks

and holes causes premature breakdown of the

pavement. Control with presurface and postsur-
40 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

face applications of herbicides. Shoulders immediately adjacent to the trafficway, medians separating divided highways, and islands at highway

intersections are often surfaced with asphalt. On

such areas, apply the herbicide to the gravel base

just before it is "shot" with asphalt. A standard

highway watering truck can be adapted for this

use by equipping it with a loading pump to circulate the spray material and standard asphalt

nozzles that deliver a fan spray.

Several herbicides prevent the emergence of

plants through the pavement, but they vary in

cost and in injury to vegetation adjacent to the

paving. The plant growth on the unpaved area,

particularly on fill slopes, may be desirable to

prevent erosion. The following products control

vegetation at the accompanying rates per footmile, (Eates per foot-mileX8.25=rate per acre.)

Chlorate-borate, 200 pounds

(25 percent sodium chlorate)

Dalapon, 10 pounds

Dalapon-silvex, 2.5 gallons

(4 lb. dalapon + ^/^ lb. silvex per gallon)

Diuron, 5 pounds

Erbon, 5 gallons

(41b. pergal.)

Monuron, 5 pounds

MonuronTCA, 0.9 gallon

(3 lb. pergal.)

TCA, 25 pounds

Postpaving treatments will be necessary later

to prevent encroachment from unpaved areas and

to control vegetation growing up through cracks

in old pavements. Use repeated spray treatments

with dalapon-silvex mixture or use dalapon on

grasses and 2,4-D or amitrole on broad-leaved

weeds.

Caution.—Erbon, monuron, and chlorate-borate

mixture may injure vegetation some distance from

the edge of the pavements, and monuron, diuron,

and monuronTCA may injure trees adjacent to

the treated area.

Railroads

There are three rather distinct areas on railways on which weed control is necessary: the

ballast, the roadbed, and the right-of-way. The

ballast is a strip 12 to 16 feet wide, made up of

coarse material, such as cinders or gravel, that

should be kept free from weeds. Because it is so

porous, it does not retain chemicals well. Insoluble herbicides, those absorbed through leaves,

and contact herbicides are most suitable. The

roadbed (berm) beyond the ballast requires weed

control, but elimination of vegetation increases

erosion. The rest of the area to the right-of-way

fence is similar to roadsides. If control is effected

during the first 2 years by heavy rates of application, it can be maintained with reduced rates

thereafter. The effectiveness of some soil sterilants like diuron and simazine may not show up

until the second or third year of use, especially

in dry areas or with deep-rooted weeds.

Apply 5 to 8 gallons dalapon-silvex mixture,

in 150 to 300 gallons water per acre-mile on ballast and berm areas or 5 to 6 quarts DNAP and

300 gallons diesel oil per mile on roadbed. For

heavy growth, add 300 gallons water.

Specific treatments adapted to different regions

of the United States (fig. 1) follow. Eates are

in pounds per acre in terms of acid equivalent

for dalapon, silvex, 2,4-D, and TCA. All others

are pounds per acre of active ingredients except

oil-PCP, which is in gallons per acre of product.

Kegion 1.—^Dalapon, 40 pounds, plus silvex, 4

pounds; or oil-PCP, 20 gal., plus 2,4-D, 4

pounds, plus monuron, 8 pounds.

Eegion 2.—Dalapon, 16 pounds, plus erbon, 20

pounds, plus 2,4-D amine, 4 pounds; or dalapon, 20 pounds, plus simazine, 4 pounds, plus

2,4-D, 4 pounds ; or dalapon, 20 pounds, plus

monuron, 8 pounds, plus 2,4-D, 4 pounds.

Kegion 3.—^Dalapon, 10 pounds, plus 2,4-D, 2

pounds; or dalapon, 10 pounds, plus amitrole,

5 pounds ; or oil-PCP, 48 gal., plus monuronTCA, 21 pounds. Apply twice a season. Add

10 pounds diuron or simazine to these sprays

to increase amount and length of control.

One application of amitrole, 5 pounds, plus

TCA, 20 pounds, plus diuron, 20 pounds,

often provides control for an entire season.

Region 4.—^Dalapon, 20 pounds, plus 2,4-D, 4

pounds, applied three times; or oil-PCP, 100

gallons, applied twice.

Region 5.—^Dalapon, 40 pounds, plus 2,4-D, 6

pounds.

Region 7.—Oil-PCP, 20 gal., plus 2,4-D, 4 pounds,

plus monuron, 15 pounds.

Reinfested Areas

To kill annual weeds and seedlings of biennials

and perennials that reinfest an area, use 2 pounds

2,4-D and 20 to 30 pounds dalapon and 1 cup

wetting agent in 50 gallons water per acre. For

species resistant to 2,4-D, use amitrole at 4

pounds, active ingredient, in 100 gallons water

per acre. Repeat applications as necessary.

For use of soil sterilants to prevent reinfestation refer to page 33.

WOODY PLANTS

Both selective and nonselective kills of woody

plants can be accomplished with chemicals.

Where a selective kill of certain species is desired,

2,4-D, 2,4,5-T, silvex, and amitrole are most com-
HERBICIDE MANUAL 41

monly used. Ammonium sulfamate, monuron,

diuron, and fenuron kill nonselectively. There

are several methods of treating woody plants:

foliage applications, basal-bark applications,

stump applications, cut-surface applications, tree

injections, and soil applications.

Foliage Applications

Make foliage applications in the active growing season after the leaves are full size. Soil

moisture adequate for ffood growth and complete

coverage are essential for satisfactory kills. Use

a boom sprayer for large areas; spray individual

plants or small groups with a hand boom from

a power sprayer or a truck. Airplanes and helicopters are also used for control. Repeated annual treatments are required if eradication is

wanted. E-educe the drift hazard in aerial spraying by using a 1:4 oil-water emulsion instead of

oil alone. Foliage applications are the cheapest

method, but often they are objectionable because

of drift hazards and the unsightliness of defoliated or dead trees. They are most practical for

controlling plants that can be covered thoroughly

from the ground. A variation of this treatment

is the stem-foliage application, in which both

stems and leaves are wet to the point of runoff.

It is sometimes more effective than basal sprays

on root-suckering species. The important consideration is to wet all the leaves thoroughly.

Wetting of the stems is incidental. The spray

volume depends on the height and density of the

brush and varies from 100 to 400 gallons per acre.

2,4-D and 2,4,5-T

Species tolerant to 2,4-D and requiring heavy

rates or repeated annual treatments are: birch;

buckbrush, snowberry ; buckeye, California ; ceanothus, varnishleaf; chamise; chaparrel; chinquapin; creosotebush; dogwood; elderberry; gorse;

greasewood; hawthorn, fleshy; honeysuckle; ivy,

English ; locust, black ; madrone ; manzanita ; oak,

Oregon, post, shinnery, Turkey, and white; poison-ivy; poison-oak; rabbitbrush, grey and yellow; redwood; rose, Cherokee, Macartney, and

prairie; sagebrush, fringed and silver; snowbrush; sumac, Chinese; tamarack; thimbleberry;

tree-of-heaven ; trumpetcreeper ; Virginia-creeper ;

and whitethorn.

Species tolerant to 2,4,5-T and requiring heavy

rates or repeated annual treatments are: basswood; bearberry; buckbrush; coralberry; cactus,

pricklypear; catclaw, mimosa; chamise; chapparel; cherry; chestnut; chinquapin; coffeetree;

cottonwood; coyotebrush; creosotebush; dogwood; elm; gallberry; gorse; groundcherry,

clammy; gum, black; hawthorn, fleshy; hazel;

hickory ; honeylocust ; honeysuckle ; hophombeam; larch; madrone; manzanita; maple; mesquite, honey and velvet; oak, black, blackjack,

bluejack, gambel, live, Oregon, red, scrub, and

Turkey; palmetto, saw; persinmion, common;

pine, lodgepole; plum, chickasaw; prickly-ash;

rose, California, Cherokee, Macartney, multiflora,

and Woods; saltcedar; skimkbrush; tamarack;

tarbush; toyon; trumpetcreeper; and whitethorn,

mountain.

Spray with 2,4-D if the species are susceptible

to this herbicide, since it is cheaper than Sj^jö-T.

Most hardwood species, however, are more susceptible to 2,4,5-T. For mixed species, use a mixture of 2,4-D and 2,4,5-T (brush killer). Spray

when plants are in full leaf and growing. If the

browning of trees and brush is not objectionable

and if drift damage is unimportant, spray in

early summer. If these objections are important,

spray in late summer and add oil, especially if

oaks are present. Dead brush can be knocked

down by equipment.

In general, esters are the most effective formulations for brush control. The diamine salt formulation, however, appears to be equally effective. Apply 3 to 4 pounds 2,4-D, 2,4,5-T, or 2,4-D

and 2,4,5-T mixture per 100 gallons water for

susceptible species and brush. (See Weed Species

and Herbicides for Control, p. 58.) Eepeated annual treatments are necessary for hard-to-kill

species. Aerial sprays of 2 to 3 pounds per acre

2,4,5-T in a total volume of 5 gallons per acre

are satisfactory if drift hazard to crops can be

avoided.

All rates of 2,4-D and 2,4,5-T are in terms of

acid equivalent.

Specific recommendations for the seven regions

of the United States follow. (See fig. 1, p. 42.)

Kegions 1 and 2.—For most brush, use 2,4,5-T;

but, for buckbrush and hazel, use 2,4-D in

mid-June. Hazel starts regrowth the year

after treatment, but there is a release period

of 5 to 8 years. For hard-to-kill species, use

a stem-foliage spray—3 to 6 pounds 2,4-D

and 2,4,5-T mixture in 10 to 25 gallons oil

and enough water to make 100 gallons of

spray. Wet leaves and stems thoroughly.

For elderberry, elm, eastern redcedar, sassafras, sumac, sweetgum, sycamore, walnut,

wild plum, and a topkill of honeysuckle, use

up to 8 pounds per acre.

Region 3.—For late summer spray, use 3 to 4

pounds 2,4,5-T in 25 gallons oil plus 75 gallons water for the carrier. 2,4,5-T is more

effective than 2,4-D on blackberries and other

brambles, common persimmon, and prairie

rose. 2,4-D is more effective on buckbrush

and skunkbrush. Aerial sprays are satisfactory, but cotton is especially susceptible to

drift damage so that extreme precautions

must be used.
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Figure 1.—^Regions of somewhat similar soil types, climate, vegetation,

and growing season.
HERBICIDE MANUAL 43

Region 4.—Use 2,4,5-T at 2 pounds per 100 gallons

water for alder; bluejack, post, and Turkey

oak; and persimmon. Apply on Turkey oak

in May or June and on persimmon and post

oak in July or August. Use 11/2 to 2 pounds

2,4,5-T in 5 to 6 gallons of oil-water emulsion per acre for most deciduous upland

hardwoods but not pines. For resistant species, use 8 to 10 gallons per acre.

Region 5.—Apply 2,4-D and 2,4,5-T mixture at

3 to 4 pounds per 100 gallons water to brush

for control of willows and cottonwood ; apply

2,4,5-T at the same rate for chokecherries and

wild rose. Use 2,4-D at 2 pounds per acre to

control sagebrush.

Region 6.—^Apply one-third pound 2,4,5-T per

acre in oil-water emulsion to original growth

of mesquite; use one-half pound per acre on

regrowth. These treatments completely defoliate the plant and kill up to 35 percent of

the roots. For dense stands, use three-quarter

pound 2,4,5-T in 2 gallons diesel oil plus 8

gallons water per acre. Use one-half pound

2,4,5-T in oil-water emulsion for shmnery

oak, and apply annually for 3 years. Use

2,4,5-T in oil-water emulsion on post oak,

and apply 2 successive years. Use 1 pound

2,4-D for sand sagebrush.

Region 7.—For general spraying, apply 2 pounds

2,4,5-T and 2,4-D mixture in 1 gallon diesel

oil plus enough water to make 40 gallons per

acre. For coyotebrush, 10 gallons spray per

acre is enough. For willow, use 100 gallons.

For aerial spraying in California, use 10 gallons spray per acre. Dissolve 2 to 4 pounds

2,4,5-T and 2,4-D mixture in 1 gallon diesel

fuel oil and mix with enough water to make

10 gallons spray. For individual plants use

4 pounds 2,4,5-T and 2,4-D mixture in 1 gallon diesel oil plus 98 gallons water. For

dormant spray, use 8 pounds 2,4-D and

2,4,5-T mixture in 98 gallons diesel oil for

deciduous trees and 4 pounds per gallon diesel oil in 90 gallons water for evergreens.

Cover well.

Amitrole

In general, spray the foliage of susceptible species with 3 to 6 pounds, active ingredient, per acre

in water. The volume required varies from 100

gallons (average) to 500 gallons (for solid

stands) per acre.

Hard-to-kill species are: aspen, blackberry,

hickory, common persimmon, and sumac.

Caution.—Although the danger from drift is

less with amitrole than with 2,4-D and 2,4,5-T,

follow directions for reducing drift (pp. 30 and

46).

Ammonium sulfamate

(WSA designation, AMS)

Apply 60 to 80 pounds 95-percent product per

100 gallons water for foliage spray when brush

or trees are in full leaf. Add 4 ounces spreadersticker per 100 gallons to increase wetting and

retention of spray. Wet leaves and stems thoroughly. In dense brush, 400 to 450 gallons spray

per acre may be needed. In South Carolina,

Missouri, and Mississippi, use 1 pound per gallon.

For re-treatments of surviving growth and seedlings, use only one-fourth to one-third the original amounts. Ammonium sulfamate can be applied successfully with a mist blower; use 360

pounds ammonium sulfamate plus 1 quart spreader-sticker plus 5 gallons No. 2 fuel oil plus 1 pint

emulsifying agent plus enough water to make 100

gallons. Typical species controlled are: cherry;

hickory ; maple, bush ; oak, red and white ; poisonivy; sassafras; and willow.

Hard-to-kill species are : ash ; basswood ; buckeye ; caragana ; euonymus ; fir, balsam ; hawthorn ;

honeylocust; juniper; locust, black; sumac, Chinese; and tree-of-heaven.

Caution.—^Avoid long contact with strong solutions. Do not use near metal pipes and tanks.

Coat exposed metal parts of spray equipment

with acid-resistant paint or rubberized undercoating used on automobiles. Wash truck and spray

rig with spray gun when refilling the tank and

at end of day. Cover metal surfaces with light

oil on weekends. At end of season, wash inside

and out and cover metal surfaces with light coating of oil. Whenever possible, use copper, stainless steel, bronze, or aluminum, but not brass, for

sprayer parts.

Ammonium sulfamate is not hazardous to wild

life. Drift from mist blowers is very dangerous.

Silvex

Use at about the same rates, acid equivalent, as

2,4-D and 2,4,5-T. In Florida, use 3 pounds per

acre, and apply annually, for bluejack and Turkey oak and persimmon. In Oklahoma, use the

low-volatile ester for chittam, elm, oaks, and redbud.

Hard-to-kill species are: blackberry; cactus,

pricklypear; cherry; creosotebush ; dogwood;

^roundcherry, clammy and purple-flower; gum,

black; hickory; manzanita; mesquite, honey and

velvet; mulberry; oak, blackjack, bluejack, scrub,

and white; Osage-orange; persimmon; rose, Macartney and multiflora; sagebrush, big; sweetgum; tarbush; toyon; whitethorn (Acacia constricta) ; yerba-santa ; and yucca, soapweed.

Caution.—^Avoid drift (pp. 30 and 46).

Dalapon and trichloroacetic acid (TCA)

Use either dalapon or TCA for control of conifers. Jack pine, white pine, and white-cedar are
44 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

most susceptible. Spruce is harder to kill. Species tolerant to both chemicals are: goldenchaintree, Norway maple, pagodatree, and virginal

mockorange. Euonymus is tolerant to TCA.

Use 15 to 25 pounds, acid equivalent, per 100

gallons water. Applications are effective only

during the growing season. For information on

handling, see pagBs 36 and 37.

Trichloroacetic acid (TCA) and 2,4-D or 2,4,5-T

Combine 2,4-D or 2,4,5-T with TCA to kill tag

alder, quaking aspen, and willow. Applications

are effective only during the growing season. For

information on handling, see pages 23 and 36.

Basal-Bark Applications

Basal-bark applications are made to the base

of tree trunks and brush stems 6 inches or less in

diameter. They are effective on either dormant

or growing plants. Treatments are most successful if applied in warm weather. Basal treatments

are well suited for uncut brush and regrowth

from cut brush or trees and particularly for selective control. The method is slightly more expensive than foliage applications and in dense stands

is more difficult. It is more effective on hard-tokill species than foliage applications, but it may

be less effective on root-suckering species like

willows, sumac, and sassafras.

In general, 2,4,5-T is better than 2,4-D or a

mixture of 2,4,5-T and 2,4-D for control of most

hardwood species, but there are some exceptions.

The esters of 2,4-D are satisfactory for cottonwood and willow- For most situations, apply

2,4,5-T at 12 to 16 pounds in 96 gallons diesel

fuel oil or kerosene. Cover all exposed bark just

above the ground line, and apply enough volume

to permit the spray to run down the bark to the

bud zone. Old or rough bark requires a larger

volume than young or smooth bark.

Specific recommendations for regions 2, 3, 4,

and 7 follow.

Region 2.—In the northeast, make basal-bark applications with a solution of 16 pounds of

2,4,5-T in 100 gallons diesel fuel oil at any

time of the year for practically all trees except those that produce root suckers. These

are most easily eliminated by late-summer

applications.

Regions 3 and 4.—^Use basal sprays of 16 pounds

2,4,5-T in 100 gallons diesel fuel oil for oaks,

gums, elms, and other hardwood brush species. In Oklahoma use frill applications for

elm. Apply to trees less than 6 inches in

diameter.

Region 7.—In California, use the cut-surface

method for trees over 2 inches in diameter.

For small trees, use 16 pounds 2,4,5-T in 100

gallons diesel fuel oil and apply 2 to 3 fluid

ounces per inch of stem diameter.

Stump Applications

Stump applications are made to freshly cut

stumps. The top and all sides of the stump to

the ground line and any exposed roots must be

wet thoroughly. In general, use the same spray

solution of 2,4,5-T or 2,4-D for stump applications as for basal-bark treatment. Use 1 pint

spray per 6 inches of stem diameter. Treatments

are most successful if applied in warm weather.

For stump treatment of ash, boxelder, cottonwood, maple, plum, and willow, use crystals or a

concentrated solution of 4 to 6 pounds ammonium

sulfamate per gallon of water. Use crystals for

small stumps under 2 inches; cover the freshly

cut surface with 1 tablespoon per 2 inches of

diameter. Spray or paint larger stumps with

the solution; wet the entire surface thoroughly.

Sodium arsenite is used to a limited extent on

stumps. Wet the tops thoroughly. Eucalyptus

and willow are hard to kill.

Caution.—For precautions in handling ammonium sulfamate and sodium arsenite, refer to

pages 43 and 33, respectively.

Cut-Surface Applications

Cut-surface applications are made in frills, or

girdles, or in cups or notches.

The frills, or girdles, are made with an ax

through the bark and well into the wood; space

them so that the ax cuts overlap and completely

encircle the tree. This method is used on individual trees too large—usually over 6 inches in

diameter—or too thick-barked to be killed by

basal-bark treatments. It prevents sprouting of

standing trees more effectively than the cut-stump

method.

Rates of application and preference of formulation varies among the regions. In general, use

16 pounds 2,4,5-T or 2,4,5-T and 2,4-D mixture

per 100 gallons diesel fuel oil. In Minnesota, use

the low-volatile esters of 2,4-D for cottonwood

and willow. In Oklahoma, use frill applications

rather than basal-bark treatments on elm. In

California, use the frill method for trees over

2 inches in diameter. Treatments can be made at

any time of the year.

For cups or notches, use crystals of ammonium

sulfamate. Space cups or notches about 6 inches

apart around the base of stems or trunks and

apply one-half ounce crystals per notch to trees

not over 10 inches in diameter. Treat at any time

of the year. Use a water-soluble dye to mark

trees that have been treated.
HERBICIDE MANUAL 45

For frill applications to ash, quaking aspen,

hickory, maple, pecan, common persimmon, blackjack oak, post oak, red oak, and sweetgum, use

4 pounds ammonium sulfamate per gallon water.

Caution.—^For information in handling ammonium sulfamate, see page 43.

Sodium arsenite is used to a limited extent in

frills. Apply with a pump oiler. Eucalyptus and

willow are tolerant.

Caution.—Sodium arsenite is poisonous to humans and other warm-blooded animals and must

be handled with extreme care. For information

on handling, see page 34.

Tree Injections

Tree injections are simply an improved method

of making cut-surface applications; they are

made into the outer sapwood with a tree injector.

They work best on old trees; young trees sprout

from the bud zone. For most hardwoods, inject

a solution of 33 pounds 2,4,5-T in 100 gallons

diesel fuel oil or kerosene from February to August in the Southern States. Use 44 pounds

2,4,5-T and 2,4-D mixture from August to February. Make injections in the base of the stems

not more than 2 inches apart.

Soil Applications

Chemicals that are absorbed by the roots are

applied around the base of trees and brush.

Fenuron

Apply to heavy soils at any time except when

the ground is frozen. Apply to sandy soils in

spring, early summer, or just before the rainy

season in arid regions. Use either spot or broadcast method.

Spot applications are most easily made when

plants are dormant. Spread 1 to 2 tablespoons

of pellets on the ground at the base of each

clump of brush. Use 2 tablespoons for large

clumps of trees; apply to opposite sides. For

black locust, sassafras, sumac, and other species

with wide-spreading root systems, spread the

chemical over 2 to 4 square feet at the base of

each tree. For species with less root spread, cover

1^ to 1 square foot. On sloping ground, apply to

the upside slope of the clump.

For broadcast applications, spread 12 to 18

pounds, active ingredient, per acre (50 to 75 lb.

per acre of the 25-percent pellets) evenly over the

area to be treated with a hand or power spreader

or by plane. Use the lighter rates on sandy soils.

The heavier rates are required on heavy soils, on

limestone soils, on poorly drained soils, and for

the hard-to-kill species.

Black gum, hawthorn, hazel, hickory, maple.

Turkey oak, Osage-orange, redbud, seamyrtle, and

smilax are hard to kill.

Specific recommendations for regions 1,2, and 6

follow. (See fig. 1, p. 42.)

Eegions 1 and 2.—Use fenuron instead of monuron for aspen, quaking; birch; cherry; dogwood; hackberry; hawthorn; hazel; hickory;

locust, black; maple; mulberry; oak, bluejack, post, and Turkey; Osage-orange; poison-ivy; redbud; redcedar, eastern; sassafras; and shadbush. Among these species,

those that are hard-to-kill and require the

heavy rates of application are: hawthorn;

hazel; hickory; maple; oak, Turkey; Osageorange ; and redbud. Fenuron pellets control

conifers at less cost than 2,4,5-T, and applications can be made much faster.

Eegion 6.—Use fenuron instead of monuron.

Apply broadcast or by air on winged elm,

blackjack oak, and post oak growing on sandy

loams. Other susceptible species are: blackberry, boxelder, chestnut, dogwood, hawthorn, and sweetgum. Apply the pellets

broadcast at 6 to 10 pounds per acre or at

2 to 3 tablespoons per tree to defoliate mesquite.

Caution.—Follow the usual precautions about

breathing the dust and undue contact with skin,

eyes, and clothing. Do not clean equipment near

desirable plants or where the chemical may be

washed into contact with their roots.

Monuron

Apply 10 to 20 pounds, active ingredient, per

acre at any time of year except when the ground

is frozen. The light rate is adequate for most

species including Turkey oak. Use 20 pounds for

2-year control. Encircle the base of the plant.

Use 2 teaspoons per plant for multiflora rose in

Northeastern United States. In Alabama, use 7

to 8 pounds per acre for Cherokee rose. In Virginia, apply 1 teaspoon monuron in pellets or

slurry per clump of brush on such species as

hickory, red and white oak, sassafras, and sourwood. Use 2 teaspoons for dewberry, black locust, persimmon, and seamyrtle. The slurry is

made of equal parts of monuron and water. In

Massachusetts, use the slurry for groundjuniper.

Caution.—For precautions in handling, see

page 35.

FenuronTCA

Apply 80 to 120 pounds, granular formulation,

per acre broadcast for brush and other weeds or

6 to 9 gallons liquid in enough water or oil to

cover well—76 to 150 gallons per acre. For small

areas, use one-quarter to one-half pound per

square foot or 2^^ to 5 cups liquid in 2i/¿ to 5

gallons water or oil per 1,000 square feet. For
46 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

spot or basal application to brush, use 1 to 3

ounces per clump or 2 to 3 tablespoons undiluted

liquid fenuronTCA per clump. Apply in a circle

halfway between the trunk or center of the clump

and the drip area. Or dilute liquid fenuronTCA

in the proportion of 1 quart formulation to 21/2

gallons water or oil and apply to the base and

root area of the plant. About 75 to 150 gallons

oil per acre are required—amount depends on

density of vegetation. The liquid formulation is

generally preferable in the Southeast ; but, where

a rapid knockdown of weeds is unnecessary, the

granular product is better for brush control.

Caution.—Do not drain or flush equipment on

or near croplands, lawns, trees, or other desirable

plants or on areas where roots of desirable plants

may extend. Prevent drift. Thoroughly clean

application equipment with water and a detergent to prevent corrosion. FenuronTCA is harmful if swallowed and is irritating to skin and eyes.

Applications Along Roadsides and Utility Lines

Herbicides are useful in the maintenance of

roadsides and utility lines if properly applied.

The greatest dangers come from drift, runoff,

improper application, and leaching to roots of

desirable species under the treated area.

Before spraying, make a survey of the area,

spotting slopes subject to erosion, location of desirable vegetation, and density and height of

brush.

Caution,—Drift hazards are greatest when

growth-regulating herbicides such as 2,4-D,

2,4,5-T, and silvex or contact herbicides are used

as sprays, but damage often results from careless application. Drift occurs not only with volatile herbicides, such as the esters of 2,4-D and

2,4,5-T, but also with any spray that has been

atomized into a mist by high pressure and small

nozzle oxDening. The volume of spray per unit

area also influences drift. Where there are adjacent susceptible plants, use at least 10 gallons

per acre and move sprayer at slow speed. It is

especially important to reduce mist when spraying with a handgun. Operate at low pressure

(30 to 60 p.s.i.). Direct spray downward as

much as possible, and do not spray when windy.

When treating edges of roads, spray from the

outside toward the pavement. Eunoff is an important hazard on slopes, bare ground, and pavements. Cut-back asphalt, applied with a soil

sterilant, helps to hold the chemical in place.

Use 39 gallons per 1,000 square feet, or 1,700

gallons per acre, or use a light covering of road

oil. If there has been an excavation, add a layer

of crushed rock. Trees and shrubs some distance

from soil treated with soil sterilants may be

killed if their roots extend below this area.

Stump, basal-bark, and foliage applications are

most suitable for the control of brush and trees

along roadsides and utility lines.

Stump applications are most satisfactory for

killing trees along roadsides and controlling

brush over 3 feet tall. Considerable labor is required, but the danger from falling branches is

removed and there are no standing dead trees.

Use esters of 2,4,5-T or 2,4-D plus 2,4,5-T at any

time of year or ammonium sulfamate during the

growing*^ season. For rates of application, see

page 4-1. Sodium arsenite can be used where the

hazards of poisoning are not important.

Basal applications are practical for uncut

brush and for regrowth from cut brush or trees.

Make applications during the dormant season to

avoid danger of injury from drift. Use esters

of 2,4,5-T or 2,4-D plus 2,4,5-T. For rates of application, see page 44.

Applications made in frills or girdles are more

effective than basal treatments on large or thickbarked trees, and they prevent sprouting more

effectively than stump treatments. Use 2,4,5-T

or 2,4-D plus 2,4,5-T. For rates of application,

see pages 44 and 45. ApjDly ammonium sulfamate and sodium arsenite in the same manner

as for stump treatments.

Roadsides

For brush after an initial clearance:

Oaks and maples.—(1) Use basal spray on

clumps for maximum kill and minimum regrowth. Follow with basal sprays on nonsuckering species or stem-foliage sprays on suckering

species. Or, (2) use large volumes of stem-foliage

spray. Follow in 2 to 3 years with a basal spray.

Suckering species.—Use overall stem-foliage

spray. On susceptible species, repeat the following year; on resistant species, use basal sprays

as followup.

For dense brush after hand cutting or light

foliage spray:

Oaks and maples.—Drench the base of stems

and stumps. Thoroughly wet the base of saplings

that are not cut. Follow in 2 to 3 years with a

basal spray in summer.

Siwkering species.—Use overall stem-foliage

spray. On susceptible species, repeat the following year; on resistant species, use basal sprays as

followup.

For foliage applications, use esters of 2,4,5-T

and 2,4-D on most species. (See p. 41.) Silvex

is better on some oaks and locust. (See p. 43.)

Use amitrole for white ash, black locust, poisonoak, and poison-ivy. (See pp. 43 and 48.) Use

ammonium sulfamate in areas where drift from

2,4-D or 2,4,5-T is too hazardous. It can be used

successfully in a mist blower in areas where

ordinary application methods are difficult. (See

p. 43.) •
HERBICIDE MANUAL 47

Fenuron or 2,3,6-TBA in dry form controls

lateral root-sprouting species such as sumac, black

locust, sassafras, and persimmon more effectively

than foliage applications of 2,4-D and 2,4,5-T.

Desirable trees adjacent to the right-of-way may

be injured. (See p. 45.)

Utility Lines

Make two complete sprayings of all transmission lines at 2-year intervals—the first to kill as

much growth as possible and the second to kill

escapes and resistant species. Spray only those

species that grow tall enough to interfere with

the lines. If they are over 6 feet tall, cut and

spray the stump.

Fenuron pellets at I214 pounds per acre, active

ingredient, kill alder, blackberries, and sumac;

elderberry, elm, hawthorn, maple, or willow are

not killed, but all species are defoliated.

TCA and dalapon are moderately effective on

conifers.

Foliage sprays of 2,4,5-T at 21/2 pounds per

100 gallons water control many species of hardwood brush throughout the season. They are

most effective when applied soon after leaves are

fully expanded and when the plants are growing

actively. Esters of 2,4-D plus 2,4,5-T in equal

proportions (brush killer) kill alder, smooth and

staghorn sumac, and willow.

WEEDS IN WOODY PLANTINGS

When shrubs or trees are to be planted along

a highway, in ornamental nurseries, for a windbreak, or other functional use, weeds can be controlled with chemicals until the plantings become

established. There are three methods of application.

Preemergence.—Apply before weeds emerge or

after they have been destroyed by cultivation.

Apply as a spray or in dry form around the base

of well-rooted 1-year-old shrubs or trees. Do not

spray foliage, and apply granular materials to

foliage only when dry. Except in areas of low

rainfall, use diuron at 1 to 2 pounds or simazine

at 2 to 4 pounds. Use DNBP at 9 to 12 pounds.

Postemergence.—Apply to young weeds at the

base of established shrubs or trees. Wet thoroughly, but keep spray off the plantings. Use 5

to 10 pounds dalapon or 4 to 6 pounds amitrole

in 40 to 50 gallons water per acre. Dalapon kills

grasses; amitrole kills both grasses and broadleaved weeds.

Preemergence and postermergence.—Apply to

weeds when young. Wet thoroughly with combinations of chemicals given above. Examples

are: 2 to 4 pounds amitrole plus 2 to 4 pounds

simazine per acre or 5 to 10 pounds dalapon plus

3 to 6 pounds DNBP per acre.

Use knapsack sprayers, hand-boom off-power

sprayers, or hand dusters. Granular formulations

are safer than sprays, but they are not used postemergence.

All woody species are tolerant of DNBP, but

the period of weed control is short. Those known

to be uninjured by recommended rates of diuron

or simazine are:

Broom {Genista tinctoria)

Burning-bush, European {EuonyTnus

europaea)

Honeysuckle, common {Lmiicera tartárica)

Honeysuckle, Zabel [L. korolkowii)

Maple, English hedge {Acer campestre)

Mockorange, Lemoines {Philadelpfms

lemoines)

Pea-tree, Siberian {Caragana arhorescens)

Spurge, Japanese {PacKysandra terminalis)

Willow, arctic {Salix pupurea 'nana')

Ninebark (Physocarpiis opulifolius)^ Korean

spiraea {Spiraea trichocarpa) ^ Spiraea media,

and Preston hybrid lilac {Syringa prestoniue)

are injured by both diuron and simazine. Diuron

injures newly planted evergreens.

Species in which simazine can be used safely

when the plants are a year or more old are :

Arborvitae {Thuja occidental¿s)

Barberry {Berberís spp.)

Boxwood {Bicœus spp.)

Chamaecyparis {Okama-ecyparis spp.)

Cotoneaster {Cotoneaster s^]^.)

Dogwood {Oomus spp.)

Douglas-fir {Pseudotsuga)

Fir, balsam {Abies balsamea)

Fir, Fraser {A. fraseri)

Hemlock {Tsuga^^^.)

Juniper {Juniperus spp.)

Pine, mugho {Pinus mugho)

Pine, red {P. resinosa)

Pine, Scotch {P. sylvestris)

Pine, white {P. strobus)

Privet {Ligustrum spp.)

Rose, multiflora {Rosa multißora)

Spruce, blue {Picea pungens)

Spruce, Norway {P. abies)

Spruce, red {P. rubra)

Spruce, white (P. glauca)

Yew {Taxus spp.)

PoisoN-IvY, POISON-OAK, AND POISON-SUMAC

There are four satisfactory herbicides for killing poison-ivy, poison-oak, and poison-sumac—

amitrole, ammonium sulfamate, brush killer, and

2,4,5-T. Apply when leaves are fully expanded,

and wet the foliage to the point of runoff.

Drench the stems as high as possible when the

plants are growing on a wall, and allow the ex-
48 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

cess spray to run down to the roots. Plants growing in the shade require more amitrole or brush

mixture than those in the sun.

Amitrole

Use 2 to 4 pounds, active ingredient, per 100

gallons water. Amitrole does not vaporize readily, but spray drift can damage nearby plants. If

ivy is growing on a desirable tree, cut ivy stem

at ground level in winter and treat the sprouts

after leaves come out in the spring. If ivy is

intertwined with desirable plants, paint the ivy

leaves with a long-handled brush. Mix 2 tablespoons of the 50-percent product in 1 quart water

for the paint. Cover at least one-half of the

leaves. Amitrole can also be applied dry.

Where brush is to be killed along with the ivy,

oak, or sumac, brush killer is effective on more

species than amitrole.

Caution.—^Amitrole kills most lawn grasses. It

is slow in action; effects may not show up for 2

or 3 weeks.

Ammonium sulfamate

Use 2 to 21/2 pounds, 95-percent product, in 3

gallons water and add a spreader-sticker. Ammonium sulfamate does not evaporate, but spray

drift can damage nearby plants.

Caution.—^Ammonium sulfamate sterilizes the

soil for several months. For precautions in handling, see page 43.

2,4-D and 2,4,5-T mixture (brush killer)

and 2,4,5-T

Use 2 to 3 pounds, acid equivalent, per 90 gallons water plus 10 gallons diesel oil. If any regrowth occurs, repeat the application. Brush

killer in diesel oil is also effective when applied

in late winter or early spring. Use 12 pounds

2,4,5-T per 100 gallons oil for dormant spray.

Treat poison-sumac in the dormant stage to avoid

skin poisoning.

CaMííofi.—Prevent drift by applying on calm

days and at least 100 feet from sensitive plants.

Treat in winter if sensitive plants are to be

grown nearby.

TURF WEEDS

Weeds in lawns, athletic fields, golf grounds,

parade grounds, the turf portions of roadsides

and railroad rights-of-way, and similar areas are

controlled by good maintenance practices supplemented with chemical herbicides. It is important to prevent the encroachment of weeds by

maintaining competition from vigorously growing turf grasses. The principal factors in maintenance are soil, grass, water, mowing, and pests.

Turf Management

Both the physical and chemical properties of

the soil are important. Adequate organic-matter

content, drainage, and aeration are as essential as

proper fertility. The selection of the grass or

grasses to be seeded is also important. Each type

has its requirements for optimum adaptation.

Water not only keeps plants from wilting, it is

itself a nutrient and it acts as a solvent and carrier of nutrients and food. The frequency and

height of mowing are important. The height is

determined by the kind of grass, and the frequency depends on rate of growth. Pests include

insects, diseases, and weeds. These often require

treatment beyond good maintenance practices.

Insecticides, fungicides, and herbicides are supplementary controls.

Chemical Control

Chemicals are useful for killing weeds (1) in

preparation for seeding, (2) where weeds have

become established in disturbance areas, or (3)

where, for other reasons, there is an incomplete

cover of desirable grasses.

Preplanting Weed Control

Nonselective control of weeds in turf areas is

possible only in preparation for seeding. Fumigants and the nonvolatile temporary soil sterilants dalapon and TCA are used.

FUMIGANTS

Some fumigants can be mixed with the surface

soil and sealed in with water. Others require a

gasproof cover to confine the vapor until it has

penetrated the soil. Polyethylene covers are

commonly used. Certain fumigants are injected

into the soil. Injectors may be hand operated or power driven. The hand type consists of a sharp-pointed tube that is thrust into

the ground. It has an attached funnel at the top

through which the chemical is fed. Power-driven

injectors operate by gravity feed with subsequent

coverage of the gas by plowing or by gear pumps

that force the liquid into the ground just behind

furrow openers.

Sodium-N-methyldithiocarbamate

(WSA designation, SMDC)

SMDC is most effective when a gasproof cover

is used in addition to a water seal, but it can be

used without the cover. Prepare the soil as for

a seedbed, and keep wet for 5 days before treatment. Application can be made by hand (sprinkling can or hose proportioner), by a sprinkler

system, or by injection. Directions for each

method accompany the product. Use 1 quart of

a 4-pound solution per 100 square feet.
HERBICIDE MANUAL 49

SMDC can also be sprayed in the plow sole

ahead of covering. If plantings or seedings are

to be made, cultivate the soil a week after treatment to permit escape of gas. Wait another week

before planting or sowing. If prolonged rains

follow treatment or if the SMDC has penetrated

deeply, make test plantings to determine if the

soil is toxic. In irrigated areas, meter the chemical into irrigation water continuously during

check flooding.

Turf and lawn renovation,—Treat old weedy

turfs and lawns by the hand or sprinkler method.

Rake off dead vegetation 2 weeks after treatment,

reseed area, rake lightly, and water. Bermudagrass is a special problem since a few surface

runners may survive. For this weed start treatment early enough in the summer to allow retreatment of survivors. If soil is compacted and

impermeable where bermudagrass or other perennial grass occurs, cultivate the soil before applying SMDC.

New lawns,—Cultivate soil, add manures and

fertilizers, keep damp for a week, and then add

1 quart SMDC per 100 square feet by the hand

or sprinkler methods.

Caution.—Do not apply SMDC within 3 feet

of small shrubs or within the drip line of large

shrubs or trees. If the treated area slopes toward

desirable plants, prevent runoff into the root

zones. Fumes of SMDC may bum the leaves of

established plants. If applied near trees and

shrubs, apply during a breeze as it is less hazardous than when there is little air movement. Do

not apply when the temperature is over 90° F.

SMDC and its decomposition products are irritating to eyes, skin, and mucous membranes.

Avoid inhaling mist or fumes. Use rubber boots

and rubber gloves. Wash any affected parts of

the body immediately with large amounts of

water, and remove contaminated shoes and clothing. Keep container tightly closed and away

from children, food, and feedstuffs. Wash all

equipment thoroughly with water immediately

after use. Avoid splashing SMDC on painted

surfaces.

3,5-dimethyltetrahydro-l,3,5,2H-thiadiazine-2-thione

(WSA designation, DMTT)

Apply dry or as a spray at 7 pounds per 1,000

square feet or 300 pounds per acre when soil

temperatures are 50° F. or higher. Heavier rates

are required for nutgrass. After application, mix

with soil to a depth of 6 inches and irrigate with

1 inch of water. Improved control results from

use of a polyethylene cover in addition to the

water. Plant or sow 2 weeks after application, if

the soil has been exposed to the air for at least

a week and if there have been no heavy rains or

watering; otherwise, wait 3 weeks.

Caution.—Use large nozzles and screens to prevent clogging. Keep suspension agitated. Do not

inhale the dust, avoid prolonged or repeated contact with skin, and do not swallow. Do not let

DMTT wash within 4 feet of growing plants or

closer than the drip line of trees or large shrubs.

Methyl bromide

Work heavy soils into seedbed condition to aid

penetration of the gas. Open a furrow or trench

around the margins of the area to be treated so

that the edges of the cover can be anchored. Place

supports at intervals over the area to prevent the

cover from hugging the ground and to insure

free circulation of the gas. Apply the fumigant

with an applicator as directed by the manufacturer at the rate of 1^2 pounds per 100 cubic feet

of piled soil or per 100 square feet of an area.

Apply when the soil temperature is 65° F. or

above. Remove cover in 24 hours. Seed in 48 to

72 hours after removal of cover.

Caution.—^Handle with care. Methyl bromide

is poisonous to humans and can cause serious

burns.

Chloropicrin

Apply chloropicrin with injector at 9^2 pounds

per 1,000 square feet or 400 pounds per acre;

inject at a depth of 6 inches in holes 12 to 15

inches apart. To kill surface seeds, use a gasproof cover after injection. Apply when the soil

is moist and at 65° F. or above. Expose for 3

days. For soil in piles, inject 7 cc. per cubic foot

(1 pint per 64 cubic feet) and cover with a gasproof material.

Caution.—Chloropicrin is poisonous, but it is

so irritating to nose and throat that it is its own

warning.

Carbon disulfide

Carbon disulfide gas kills on contact; hence,

thorough distribution in the soil is essential. High

soil moisture, hardpans, and tight layers of clay

interfere with its movement and distribution. Inject the liquid into holes; apply 2 ounces per hole

and space holes 24 inches apart each way for light

soils, 18 inches apart for medium soils, and 12 to

15 inches apart for heavy soils. For deep-rooted

plants, place the chemical 8 to 18 inches deep in

the soil with either a hand or power injector.

Apply in warm weather. Seal after injection by

rolling or by wetting.

Caution.—Carbon disulfide is poisonous, flammable, and explosive. Ground the barrel through

a metal bar buried in the soil.

NONVOLATILE TEMPORARY SOIL

STERILANTS

Dalapon and TCA are used as nonvolatile temporary soil sterilants.
50 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

Dalapon

Apply dalapon at 41/2 to 51/2 ounces per 1,000

square feet or 12 to 15 pounds, acid equivalent,

per acre in July to rid an area of perennial

grasses growing m moist fertile soil. Dalapon is

effective when sprayed on growing vegetation.

Usually, followup treatments are necessary in

August to kill surviving plants. Apply long

enough ahead of seeding turf grasses so that toxic

residues have disappeared. Dalapon disappears

fastest in warm humid areas and persists in dry

cool soils where the environment is unfavorable

for microbial activity. If there is adequate moisture and temperatures are warm for 3 to 4 weeks

after the last treatment, lawn grasses can then

be seeded. Dalapon injures or kills all grasses in

the area treated, and reseeding such areas will be

necessary. In semiarid regions with cold winters,

early-fall applications have usually disappeared

by late spring.

Caution.—^Avoid contact with skin and eyes

and avoid inhaling spray mist. Wash affected

parts with water if contact is made. Flush equipment with water immediately after use. Do not

allow spray solutions to stand more than 2 days

after mixing.

Trichloroacetic acid

(WSA designation, TCA)

Apply TCA at 9 to 11 ounces per 1,000 square

feet or 25 to 30 pounds, acid equivalent, per acre

to land that has been plowed or can be plowed

after treatment. Eemove trash before application. TCA is leached rapidly from well-drained

soils after heavy rainfall. Substantial amounts

are adsorbed on organic colloids so that it disappears more slowly from muck soils than sandy or

clay soils.

Caution.—Same precautions apply to TCA as

for dalapon.

Selective Weed Control

Turf weeds comprise (1) broad-leaved species

that can be killed with one group of herbicides

without seriously injuring turf grasses and (2)

undesirable grasses that can be controlled by a

second group of chemicals. The morphological

and physiological differences between broadleaved weeds (dicotyledons) and grasses (monocotyledons) make selective control possible.

Wliere weedy grasses are to be removed from

turf grasses, selectivity is accomplished usually

if the weed is an annual and the turf grass is a

perennial.

BROAD-LEAVED WEEDS

Broad-leaved weeds that are common in turf

include curly dock, common or mouse-ear chickweed, dandelion, field bindweed, heal-all, henbit, knotweed, plantain, shepherds-purse, speedwell, wild carrot, wild garlic, wild onion, woodsorrel, and yarrow.

2,4-D; MCPA; 2,4,5-T; and silvex

The four most commonly used herbicides for

control of broad-leaved weeds in turf are 2,4-D.

MCPA, 2,4,5-T, and silvex. unless a species is

more susceptible to silvex, 2,4,ö-T, or MCPA, use

2,4-D because it is less expensive. (See Weed

Species and Herbicides for Control, p. 57.) At

recommended rates none of these herbicides injures established grasses other than bents, but

they may reduce the stand of legumes. All are

growth-regulator type herbicides that may injure

susceptible plants adjacent to the area sprayed.

There is no danger of injury from vapors from

the salt formulations. The low-volatile esters are

less hazardous than the methyl, ethyl, isopropyl,

butyl, or amyl esters, but they also vaporize at

temperatures above 90° F. Drift, however, may

occur with any spray if droplets are small enough

to remain suspended in the air. Therefore, spray

with low pressures (30 p.s.i. or less) and a coarse

nozzle to reduce number of fine droplets.

A classification of weeds based on control by

2,4-D, MCPA, 2,4,5-T, and silvex foUows.

1. Weeds equally well controlled by 2,4-D,

MCPA, 2,4,5-T, and silvex: Field bindweed,

creeping buttercup, dandelion, lawn pennywort,

broad-leaved plantain, buckhorn plantain, blackseed plantain, Canada thistle, and common yarrow.

Apply 2,4-D, MCPA, or 2,4,5-T at 0.3 to 0.4

ounces, acid equivalent, per 1,000 square feet or

about 1 pound per acre. For smaller areas, use

2 tablespoons of a 4-pound-per-gallon formulation in 1 gallon water or follow instructions on

the label of the container. Spray when weeds are

growing rapidly and wet the foliage completelyApply 1 to iy2 pounds silvex per acre in Northern States and 2 to 3 pounds in the Southern

States. Yarrow is hard to kill. Repeat treatments.

2. Weeds better controlled by 2,4-D or 2,4,5-T

than by MCPA or silvex: Sulfur cinquefoil,

curly dock, and purslane speedwell.

Tops of curly dock are easily killed if sprayed

before stalks or stems appear but repeated treatments are required for root kills. Repeat treatments for speedwell.

3. Weeds better controlled by 2,4-D than by

2,4,5-T, MCPA, or silvex : Wild carrot, common

cinquefoil, wild garlic or onion, heal-all, moneywort, puncturevine, and shepherds-purse.

Wild onion and wild garlic are satisfactorily

controlled by repeated annual treatments with

esters of 2,4-D applied early in the spring. Kates

vary from 1 to 3 pounds, acid equivalent, per

acre—in Minnesota, Indiana, and Northeastern
HERBICIDE MANUAL 51

United States, use 1 pound per acre; in Virginia,

Tennessee, Mississippi, Alabama, and Oregon, use

11/2 to 2 pounds; and in North Carolina, use 3

pounds in a single application or in three treatments each year—mid-January, mid-February,

and mid-March—and apply for 3 years. If the

amine salts are used, add a detergent (i^ lb. per

50 gal. spray). Make successive applications in

the spring, the next fall, and the following spring

on new growth. Bentgrasses and some fescues are

injured at these rates.

4. Weeds better controlled by silvex than by

2,4-D, 2,4,5-T, or MCPA: Chickweed, groundivy, henbit, annual knawel, black medic, upright

spurge, wild strawberry, violet, and yellow woodsorrel.

Except in the South, repeated applications of

silvex or 2,4,5-T control common chickweed (annual ), and silvex has been effective on mouse-ear

chickweed ( perennial). ( See also DNBP, below. )

5. Weeds better controlled by silvex or 2,4,5-T

then by MCPA or 2,4-D : The clovers and ponyfoot {Dichondra repens).

Where these species are undesirable, use 1 to

11/^ pounds silvex or 2,4,5-T, acid equivalent, per

acre in the Northern States and 2 or 3 pounds in

the Southern States. For putting greens, use i/o

pound in 25 to 30 gallons water per acre. Bentgrasses and fescues are more susceptible to injury

than bluegrass. To remove burclover and whiteclover from bermudagrass and St. Augustinegrass

turf in Texas, use % to II/2 pounds per acre

silvex.

Caution.—Use light rates of 2,4-D or silvex on

St. Augustinegrass. Use one-fourth to one-half

the usual rate of 2,4-D, MCPA, or silvex on bentgrasses and new seedlings of other turf grasses.

Normal rates can be used after the second mowing. If clover is to be maintained, use one-fourth

to one-half the normal rate of 2,4-D, MCPA, or

silvex.

Dicamba

Apply dicamba at 1/2 to li/^ pounds per acre

to control prostrate knotweed. Use as a foliar

spray in fall or spring. Use at 2 pounds per acre

for wild garlic or wild onion.

Caution.—Avoid drift. (See pp. 30 and 46.)

DNBP

In the South, use DNBP for control of chickweed. Apply amine DNBP at 1 to 2 pounds per

acre in 40 gallons water. Apply when temperatures are above 60° F.

Caution.—See precautions for application,

page 39.

Methyl bromide

Methyl bromide is effective against wild garlic

and wild onion ; but application is laborious, since

the area to be treated has to be covered with a

gasproof cover. All vegetation is killed so that

reseeding is necessary.

WEEDY GRASSES

Weedy grasses common in turf include annual

bluegrass, barnyard grass, crabgrass, foxtail,

goosegrass, nimblewill, nutgrass (a sedge), fall

panieum, stinkgrass, Texas millet, wild paspalum, and witchgrass. All except nimblewill, nutgrass, and paspalum are annuals and can be

controlled selectively by treating the entire area.

Both preemergence and postemergence treatments can be used. The perennial grasses are

controlled by treating individual plants.

Preemergence control,—For preemergence control of annual species, use lead or calcium arsenate (or products containing these chemicals),

dimethyl ester of tetrachloroterephthalic acid

(DCPA), 0-(2,4-dichlorophenyl)-0-methyl isopropylphosphoramidothioate (DMPA), or chlordane.

Calcium arsenate and lead arsenate

Apply 8 to 12 pounds calcium arsenate per

1,000 square feet or 12 to 20 pounds lead arsenate

for crabgrass on low-fertility or sandy soils; 12

to 16 pounds calcium arsenate or 20 to 32 pounds

lead arsenate on fertile or clay soils. Apply 50

percent more of either for annual bluegrass.

These treatments may reduce the vigor of lawn

grass, and overtreatment ma}»- reduce stands. If

proper rates are used, the grass maintains a green

color. The effectiveness of arsenicals is greatly

reduced by phosphate in the soil. Apply only to

soils low in this nutrient, and do not spread phosphate fertilizer until the arsenic has controlled

the weeds.

Caution.—The arsenates are poisonous and

must be handled with care. Arsenic compounds

persist in the soil.

DCPA

Apply DCPA before weed seed germinates.

Mix thoroughly with enough water to provide at

least 40 gallons spray per acre. Keep the spray

suspension agitated to avoid settling. For susceptible weeds, apply 3% ounces, active ingredient,

per 1,000 square feet or 10 pounds per acre. For

barnyard grass, redroot pigweed, and upright

spurge, use 5 ounces per 1,000 square feet or 14

pounds per acre.

Caution.—DCPA prevents growth of turf

grasses if seeded soon after treatment; wait at

least 3 months. It is harmful if swallowed.

Avoid contact with eyes, skin, and clothing.

DMPA

Apply DMPA before weed seed germinates.

Use the emulsifiable liquid formulation for the
52 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

control of crabgrass, prostrate knotweed, and

nimblewill in established bluegrass turf. The

granular formulation does not control nimblewill.

It is less liable than the liquid formulation to

cause foliage burn of turf grasses. It can be

used on established turf of blue, St. Augustine,

centipede, bermuda, and zoysia grasses.

For control of crabgrass, use 5% ounces, active

ingredient, per 1,000 square feet or 15 pounds

per acre of either the liquid or granular product.

The granular product can be applied in the fall,

but it controls only the crabgrass. For control

of nimblewill, apply the liquid in May or June

and repeat the treatment about 1 month later.

Use at the rate of 1 pint (3-lb. formulation) per

1,000 square feet with enough water to wet the

foliage thoroughly (about 5 to 6 gal.) but without excessive runoff. To prepare the spray, add

one-half the required amount of water to the

tank, add the proper amount of liquid concentrate, add the rest of the water, and stir. Do not

sprinkle after treatment.

Caution.—DMPA prevents growth of turf

grasses if seeded soon after treatment; wait at

least 3 months. It is harmful if swallowed.

Avoid contact with eyes, skin, and clothing. Keep

DMPA away from heat and open flame.

Chlordane

Results with chlordane have been erratic. It is

most successful under dry conditions and low soil

fertility. Apply 2 pounds per 1,000 square feet

preemergence.

Postemergence control,—For postemergence

control of annual species, except annual bluegrass (pp. 51 and 52), use amine methylarsonate

(AMA), disodium monomethylarsonate (DMA),

or phenylmercuric acetate (PMA). Make first

application soon after emergence of the weed.

Eepeat treatments at 7- to 10-day intervals until

satisfactory control is achieved. Usually three

treatments are required.

AMA

If temperature is not over 80° F., apply AMA

to moist soil at one-half pint of 16-percent formulation in 6 gallons water per 1,000 square feet.

Wet foliage lightly. If temperature is over 80°

F., use 1 pint in 12 gallons water per 2,500 square

feet. Sprinkle 2 days after treatment.

Cautioiu—^Do not treat newly seeded areas with

AMA before the third mowing. Do not use on

centipede or St. Augustine grasses.

Avoid contact with eyes or skin. Do not inhale

spray mist. Do not take internally. Do not allow

livestock to graze treated vegetation.

DMA

Apply DMA to moist soil at 2 to 3 ounces, active ingredient, per 1,000 square feet or 5 to 8

pounds per acre to Kentucky or Merion bluegrass

and zoysiagrass sods. For fine-leaved fescues and

bentgrass, use 2 ounces and apply only in the

spring before hot weather arrives.

Caution.—^Do not use DMA on St. Augustinegrass. Avoid inhaling spray mist. Keep livestock

from grazing treated vegetation. Avoid drift.

Store in glass bottles or metal cans.

PMA

Apply PMA at one-fifth ounce, active ingredient, per 1,000 square feet or 5.4 pounds per acre.

Use half this rate on putting greens and other

areas where the grass is cut short.

Caution.—^Merion bluegrass is sensitive to

PMA. PMA is poisonous when taken internally.

Wash immediately with soap and warm water if

skin is irritated through contact.

Sodium arsenite

Sodium arsenite controls annual bluegrass. In

addition it also controls angleworms and white

grubs. Sodium arsenite can severely bum the

turf if applied in hot weather. On golf ground

fairways, use 2 pounds per acre in 75 gallons

water when temperatures are 40° to 50° F., 1^^

pounds at 50° to 65°, 1.0 pound at 65° to 75°, and

do not treat when temperatures are above 75°.

For putting greens, use three-quarter ounce per

1,000 square feet at temperatures of 40° to 50° F.,

one-half ounce at 50° to 65°, and one-third ounce

at 65^ to 75^.

Caution.—Sodium arsenite is very poisonous to

man and animals. (See p. 33.)

Treatment of individual plants,—^For treatment of individual perennial grass plants, use

dalapon or petroleum naptha (for treatment of

bermudagrass, see p. 49). Dissolve one-quarter

pound dalapon in 1 gallon water. Apply the solution to grasses at ground level. Use a cane-type

applicator, a syringe, or a wad of cotton fastened

to the end of a stick.

Petroleum naptha is effective on both broadleaved and grassy weeds. Use full strength with

same types of applicators as recommended for

dalapon.

Bermudagrass can be killed with methyl bromide (p. 49), SMDC (p. 48), or DMTT (p. 49).

Only one application of methyl bromide is required, and the area treated can be reseeded in

2 or 3 days.

AQUATIC WEEDS

The major groups of aquatic weeds are (1)

floating, (2) submersed, and (3) emersed. All

three groups may occur in agricultural watercontrol systems, ponds, and lakes.
HERBIOIDE MANUAL 53

Floating Weeds

Floating weeds germinate in the bottom of

ditch or pond, then become separated and float.

Water-hyacinth, waterlettuce, waterfern, pennywort, and rooted submersed weeds with floating

leaves such as waterlilies and watershield (in

ponds and lakes) can be controlled with 2,4-D.

Apply the amine salt formulation or low-volatile

esters at 2 to 4 pounds, acid equivalent, per 100

gallons water, except for waterfem and waterlettuce (below). Use sufficient volume to cover

foliage uniformly. Use the esters in seasons of

frequent rain. Spray during the growing season

and when the weather is warm ; use low pressure

and large nozzles. Ee-treat surviving plants in

2 or 3 weeks. Where drift is no problem, spray

by aircraft; use 60 to 80 pounds ester per 100

gallons #2 diesel fuel oil, and apply at 3 to 4

pounds, acid equivalent, per acre. The ester formulation of silvex is also effective on waterlilies

at 2.5 p.p.m.

The foliage of waterlettuce and waterfern is

hard to wet; water sprays are ineffective and

even esters in oil are not dependable. For waterlettuce, use invert emulsions (see p. 24) of 2,4-D

or 2,4,5-T; a mixture of 2,4-D and 2,4,5-T emulsified with 10 to 15 percent (by volume) diesel

fuel oil in water ; diesel fuel oil at 20 gallons per

acre; or simazine at 10 pounds per 100 gallons

water. For waterfern, use an invert emulsion of

2,4-D and 2,4,5-T at 3 to 4 pounds per 100 gallons

and completely cover the foliage. Amitrole-T at

2 to 5 pounds per acre is promising on waterhyacinth and waterlettuce.

Duckweed can be controlled with copper sulfate or 1 percent octachlorocyclohexenone (OCH)

in oil ; apply twice at an interval of 2 weeks.

Submersed Weeds

Submersed weeds include (a) rooted species

such as pondweeds, naiad, watermilfoil, watercrowfoot, waterweed, and water-stargrass, and

(b) nonrooted species such as algae.

In Ponds and Lakes

For control of rooted submersed species in still

water use one of the following chemicals.

Sodium arsenite

Apply sodium arsenite at 2 to 10 p.p.m. Use

the light rate for soft water, 4 p.p.m. for hard

water, and 8 to 10 p.p.m. for cold water. Dilute

the solution concentrate to spraying consistency

with water and spray weed beds or entire pond.

Treat shoreline areas first. Apply when weed

growth is active but before shoots have reached

the surface. Repeat applications if needed. Do

not treat ponds fed by large streams—^the chemical is diluted before it can become effective. Apply to the entire water volume when weeds are

scattered throughout the pond. If rooted weeds

or algae are concentrated near the shore, calculate the volume of water in the weed strip. To

determine the volume of water in a pond and the

amount of chemical needed, use the following :

Average depth of water, in feet, Xsurface

acreageX43,560=volume water, in cubic

feet, or

Average depth water, in feet, Xsurface area,

in square feet=volume water, in cubic

feet.

1 p.p.m.=2.7 lb. per acre-foot (43,560 cu. ft.)

Pounds chemical=p.p.m.Xacre-footX2.7

Apply 1 gallon 4-pound liquid per 16,000 cubic

feet water in the pond. If there are heavy masses

of summer algae, use 1 gallon per 10,000 cubic

feet. For a strip of underwater weeds or floating

summer algae near the shore, use 1 gallon 4-pound

liquid per 6,500 cubic feet if pond is large and

unprotected from wind and waves or per 8,500

cubic feet if the pond is small and protected. For

application, dilute sodium arsenite with water in

proportion of 1:3 or 1:4. Spray only one-half of

area; treat the rest 7 to 10 days later» At rates

effective on most underwater species, sodium arsenite is not toxic to fish, but they may be killed

if an excess of weed decay removes oxygen from

the water.

Water-hyacinth, algae growing below the surface, and other aquatic plants that have a waxy

leaf covering are not killed by sodium arsenite

at these concentrations.

Caution.—Inorganic arsenical compounds are

caustic poisons and must be handled with extreme

care to avoid injury or death to human beings,

livestock, or game animals. See page 33 for handling. Do not use water for bathing, sprinkling

of lawns and gardens, or watering of ammals for

3 days after treatment. Treated water must be

quarantined 2 weeks before it is safe for drinking.

Do not use the arsenical treatment in any waters

intended for rice culture. Carefully observe all

State laws on applications of arsenicals.

Where the danger of poisoning from sodium

arsenite is too great, the following herbicides can

be used.

2,4-D

2,4-D in pellet or granular form can be used in

still water for broad-leaved submersed and

emersed aquatic plants. Apply 150 pounds of the

pellets containing 20 percent, acid equivalent, per

acre for young, susceptible species and 200 pounds

for more resistant kinds or in extremely acid or

alkaline water.

Coontail, fanwort, and watermilfoil are easily

controlled; wavy-leafed pondweed, some other
54 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

pondweeds, bladderwort, and waterweed {Elodea) are more difficult.

Silvex

Use the granular potassium salt of silvex at

2 to 3 p.p.m.; the liquid at 4 p.p.m.; and lowvolatile ester at 2.5 p.p.m. for arrowhead, coontail, fanwort, some pondweeds, some buttercups,

and watermilfoil.

Endothall

For most Potamogetón pondweeds, horned

pondweed, and coontail, use at 1 to 2 p.p.m. in

large areas and 2 to 3 p.p.m. for spot or lakemargin treatment. Use 2 to 3 p.p.m. in large

areas and 3 to 4 p.p.m. for spot treatment for

watermilfoil. Use 3 to 4 p.p.m. and 4 to 5 p.p.m.,

respectively, for burreed. Use 25 p.p.m. for

arrowhead in large areas and for spot treatment.

Caution.—Avoid contact with skin and eyes.

Avoid breathing spray mist. Bathe and change

clothing at least daily while using. In case of

contact with the skin, immediately flush exposed

areas with plenty of water for at least 15 minutes; get immediate medical attention if eyes are

affected. If chemical is swallowed, take cold milk

and Amphogel (1 oz.) instead of an emetic. Call

a doctor immediately.

Prevent drift. Wash equipment thoroughly

with water after each application. Do not use

treated water for irrigation, agricultural sprays,

or domestic purposes within 7 days after treatment. Do not use fish from treated water for

food or feed within 3 days after treatment. Obtain necessary approval and permits for use in

States or areas where required.

Dichlone

For control of rooted species such as coontail,

naiad, parrotfeather, pondweeds, and watermilfoil, use dichlone at 10 to 20 pounds per surface

acre. At these rates, concentrations of the chemical range from 2.7 to 10.8 p.p.m. in water 5 to 10

feet deep. Toxicity of dichlone to fish has been

variable, and safe concentrations have not definitely been determined.

For control of blue-green and filamentous green

algae, use dichlone at 1 pound per surface acre

water (0.01 p.p.m.). Repeat applications to

maintain control.

Caution.—It may be dangerous to trout at 0.05

p.p.m. Consult Federal or State Fish and Wildlife Service for information relative to fish.

Diuron, fenuron, monuron, simazine, fenuronTCA,

and monuronTCA

Use these chemicals preemergence at 20 to 40

pounds per acre, or 1 to 5 p.p.m., on coontail and

naiad and pondweeds {Najas spp. and Potamogetón spp.).

Diquat

Use diquat at 5 p.p.m. for most algae {Aimhaena, Chara spp., Cladophora, Hydrodictyon^

and Oscillatoria). Use 8 pounds, active ingredient, per gallon water for diapedium or dianthera

{Justicia spp.). Use 1 p.p.m. for sago pondweed

{Potamogetón pectinatus) and leafy pondweed

{P. foliosus). Use 3 to 4 p.p.m. for buttercup

{Banimculus spp.) and waterweed {Elodea canadensis). Use 10 pounds, active ingredient, per

100 gallons water for arrowhead.

Caution.—Diquat is highly toxic if swallowed.

Copper sulfate

For control of filamentous green algae, use

copper sulfate at l^ to 1 p.p.m. in soft water or

1 to 2 p.p.m. in hard water. For branched filamentous algae {Hydrodictyon) make three to five

treatments of copper sulfate at the same rate as

above on consecutive days. Apply during earlydevelopment stages of algae.

There are four methods of application: (1)

Drag a burlap bag of crystals across the pond or

lake behind a boat. Use a definite pattern to distribute the required quantity evenly. (2) Dissolve crystals or powder in water and sprinkle or

spray this solution on the water. (3) Release solution underneath the surface from either shore

or from a boat. (4) Broadcast crystals from

shore or boat. If temporary relief rather than

elimination of the algae is adequate, spray a lane

parallel to the shore 200 to 400 feet wide and

spray all protected bays. This frees the treated

area of algae, but reinfestation will occur.

Caution.—Copper sulfate is safe for most fish

at the recommended concentrations, but do not

use in trout waters since trout are susceptible to

very low concentrations. Continuous or frequently repeated applications may also control

rooted species, but they tend to be detrimental to

fish. Copper sulfate is highly corrosive to iron

and galvanized metal. Use equipment made of

red brass, commercial bronze, copper, stainless

steel, enameled ware, or wood. Do not apply on

a windy day, and avoid contact with eyes, nose,

and mouth.

In Irrigation and Drainage Systems

For control of weeds growing in the bottoms

and on lower slopes of ditches that carry water

only occasionally, apply diuron or monuron at

10 to 40 pounds, active ingredient, per acre ; simazine at 15 pounds, active ingredient; erbon at 100

to 160 pounds, active ingredient; sodium arsenite

at 300 to 600 pounds, product; chlorate-boratemonuron mixture at 500 to 1,000 pounds, product;

or borate-monuron mixture at 300 to 500 pounds,

product. Treatments are effective for 1 to 3 years.

For control at the waterline and in the bottom
HERBICIDE MANUAL 55

of ditches carrying water constantly or frequently, apply diuron at 20 to 80 pounds, simazine at 15 to 40 pounds, or sodium arsenite at

600 to 1,000 pounds when there is no waterflow.

Repeat treatments every 3 to 12 months. Frequency of re-treatment depends on the rate of

herbicide applied, the amount of rainfall, and the

amount of water that flows through the ditch

after treatment. These treatments control most

aquatic weeds rooted at the waterline.

Caution.—^Whenever possible spray when the

ditch is empty to avoid contamination of the

water. When water is present, spray upstream to

reduce the concentration of chemical in the water.

For ditchbank weeds, use herbicides that do

not have long residual toxicity in the soil. For

annual and perennial broad-leaved weeds, where

few or no weedy grasses are present and where

desirable grasses should be preserved, apply amine

salts or low-volatile esters of 2,4:-D at 1 to 2

pounds per acre during early gi'owth of weeds.

Repeat as necessary to maintain control.

For weedy grasses, apply dalapon at 10 to 30

pounds, acid equivalent, per acre; amitrole at 5

to 10 pounds, active ingredient, per acre; or aromatic oil or fortified fuel oil at 80 to 160 gallons

per acre. Amitrole and dalapon treatments are

also effective on cattails, cutgrass, and sedges.

Use the lower rates where only annual species are

present and when re-treatments are to be made.

Oil treatments must be repeated every 3 or 4

weeks to eliminate the weeds in one or two growing seasons. Usually, one or two applications of

amitrole or two to four applications of dalapon

per year will maintain adequate control. After

perennial grasses have been eliminated, add 2,4-D

at 1 to 2 pounds per acre to amitrole or dalapon

to control invading broad-leaved weeds.

For general weed control in areas where proximity to cotton, grapes, tomatoes, and other sensitive crops or ornamentals prevents the use of

2,4-D, use aromatic oil or fortified oil at 80 to 160

gallons per acre as often as necessary.

For Johnsongrass, use :

(1) Dalapon.—Thoroughly wet the foliage

with a solution of 1 pound, product, to 5 gallons

water. Re-treat whenever the grass becomes 12

to 15 inches tall; two or three treatments are

usually required.

(2) Undiluted aromatic oil,—^Apply before

grass is 12 inches tall. Re-treat whenever grass

becomes 12 inches. The number of applications

needed depends on vigor of the grass—^usually

four to nine. Apply about 160 gallons oil per

acre for the first application ; decrease the volume

as the stand of grass is thimied.

(3) TGA,—Apply to regrowth 10 to 12 inches

tall in the fall. Use 120 pounds, product, in 160

gallons water per acre.

For weedy ditchbanks where desirable grasses

are to be sown, eliminate weeds by preceding

methods. Delay sowing grass seed 1 month after

the final chemical treatment. Apply 2,4-D amine

at 1 pound per acre to grass 1 month after

emergence. Re-treat until the grass stand is established if it is necessary to control invading broadleaved weeds.

Caution,—Whenever possible, spray when the

ditch is dry to avoid contamination of the water.

When water is present, spray upstream to reduce

the concentration of chemical in the water.

For control of rooted submersed species such

iis pondweeds and waterweed and for algae in

Western and Great Plains irrigated areas, use

one of the following chemicals.

Emulsifiable aromatic solvents (methylated benzenes

such as xylene)

Apply these solvents in the canal at 5.4 to 10

gallons per c.f.s of waterflow during 30 to 60

minutes for pondweeds and waterweed. This

gives 400 to 740 p.p.m. for 30 minutes, or 200 to

370 p.p.m. for 60 minutes. Add nonionic or anionic-nonionic blend emulsifiers to solvents at a

concentration of 1 percent for waters over 70° F.,

1.5 percent for waters between 60° and 70°, and

2 percent for waters below 60° F. Repeat treatments in regions with long growing seasons.

Some of the pondweeds require up to 925 p.p.m.

(12.5 gal. per c.f.s.). The water level in the ditch

must cover weeds so that the herbicide contacts

all plants.

For steady flowing water, spray under the surface or feed into the irrigation pump intake

causing the flow. Use booster treatments of 5

gallons per c.f.s. along the ditch at intervals of

2 to 3 miles to strengthen the emulsion as it

passes. One treatment gives control for 6 to 8

weeks.

For still water or dead-end ditches, spray under

water. Apply continuously along the ditch from

equipment mounted on a boat, an airboat, or

truck. Use low and medium boiling solvents with

enough chlorinated benzenes in them to make the

specific gravity of the solvent mixture 1.01 to 1.03.

They are effective on southern naiad and other

submersed species in Southeastern United States.

For the first treatment, use 40 p.p.m.; for later

treatments, 20 p.p.m. every 20 to 24 months. In

sandy soils, use 80 p.p.m. for the first treatment

and 40 p.p.m. every 6 to 9 months. If ditches are

inaccessible, drain and refill with treated water.

Use the following formula to compute the

amount of herbicide required for a still-water

ditch :

where F=gallons of herbicide; J. =cross-section
56 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

area of ditch, in square feet; Z=length of ditch,

in feet; and 0^=desired concentration of the solvent, in p.p.m.

An application of 100 p.p.m. is equivalent to

4 gallons herbicide per square foot of cross-section area for every mile of ditch.

The warmer and more quiet waters prevalent

in water-control canals of Southeastern States

permit much longer exposure times to treatment

and make possible control of waterweeds with

much lower concentrations of herbicides than are

necessary in colder and rapidly flowing water in

canals of Western and Great Plains States. For

control of rooted submersed species such as southem naiad, coontail, and bladderwort, use emulsifiable aromatic solvents at 20 to 200 p.p.m. during a continuous treatment period of 24 to 48

hours. Gasoline mixtures with polychlorobenzenes at similar concentrations and exposure times

give good control in Florida.

Caution.—These solvents kill fish and may kill

all aquatic life. They are irritating to the skin.

Keep all fire away; the low-boiling type flashes

as easily as gasoline; the medium-boiling types

also ignite readily. Use hose and fittings that are

resistant to oil and solvent. Do not inhale solvent vapors. Naptha fumes are toxic to fish and

waterfowl.

Aromatic solvents

Apply aromatic solvents at 100 to 150 p.p.m.

during a 15-minute period for control of filamentous green algae in western irrigation canals.

Aromatic solvents usually are more economical

than mechanical methods of weed control in canals up to 70 c.f.s., and frequently they are used

in canals of 100 to 200 c.f.s where water is used

for sprinkler irrigation.

Caution.—See precautions for applying emulsifiable aromatic solvents.

Copper sulfate

Use copper sulfate for control of filamentous

green algae in water flowing at one-half foot or

more per second and apply at three-quarters to 2

pounds per c.f.s. Repeat treatments at intervals

of 2 to 6 weeks.

Caution,—See precautions on page 54.

Acrolein

Apply acrolein at 1 to 2i/^ gallons per c.f.s.

during 1 to 4 hours. This treatment has proved

even more effective than aromatic solvents. Each

application usually gives control for 4 to 8 weeks.

Caution.—Because of difficulty in handling and

its severe irritation to eyes and respiratory passages, a safe application procedure has been designed for use only by skilled operators with

specialized equipment.

Pentachlorophenol

Apply pentachlorophenol at 1-percent to 2-percent concentration for weeds protected from sun

and wind, as in deep drainage ditches. Use 2 percent to Ö percent for hard-to-kill species.

Caution.—See precautions on page 39.

In Reservoirs and Large Canals Carrying Water

for Potable or Industrial Uses

For control of algae or rooted submersed

aquatic species in slowly moving water, use copper sulfate and apply continuously. Use enough

to maintain 0.6 to 1.0 p.p.m. concentration in the

water throughout the growing season. The

amount of copper that dissolves is influenced by

the hardness of the water. Provide a concentration of 1.0 p.p.m. early in the season, and reduce

it gradually after midsummer to as low as 0.6

p.p.m. late in the growing season. These rates

give adequate control and are well below the

maximum permitted concentration of 3.0 p.p.m.

copper ion or 7.5 p.p.m. copper sulfate in potable

water supplies, as established by the U.S. Public

Health Service.

Concentrations of 0.1 to 4 p.p.m. can be lethal,

but are tolerated in hard alkaline water by resistant fish such as large-mouthed bass.

Emersed and Marginal Weeds

Emersed and marginal weeds are rooted beneath the surface but rise above the waterline.

The more common emersed species in regions of

their adaptation are alligatorweed, arrowhead,

bulrushes (or tules), burreed, cattails, emergent

parrotfeather, grasses, lotus, pickerelweed, primrose-willow, reeds, rushes, sedges, smartweeds,

spatterdock, spikerushes, swamp-loosestrife, waterchestnut, watercress, waterlilies, waterprimrose, and watershield. Alligatorweed, reeds, and

smartweeds frequently grow entirely emersed

from water on ditchbanks and wetlands with

their roots extended into saturated soil. In general, control the emersed aquatic weeds with the

same herbicides that are effective on ditchbank

weeds. (See pp. 38 and 55.)

Broad-Leaved Species

For most broad-leaved emersed species, spray

the foliage with 2,4-D, 2,4,5-T, or silvex at 2

pounds, acid equivalent, in 100 gallons water per

acre. Add 6 ounces wetting agent for plants with

waxy leaves or mix the 2,4-1) with 100 gallons

diesel oil. Eepeat application in 2 or 3 months.

Cover all leaves and stems thoroughly. Do not

spray when vegetation is wet with dew or rain.

For control of arrowhead, lotus, pickerelweed,

Pennsylvania and water smartweed, spatterdock,
HERBICIDE MANUAL 57

waterlilies, and waterprimrose, use low-volatile

esters of 2,4-D at 1 to 4 pounds per acre and

apply in oil or oil-water emulsion in sufficient

volume to cover foliage thoroughly. Of these

weeds, arrowhead and spatterdock are hardest to

kill.

Caution.—For 2,4-D in oil-water emulsions,

mix 2,4-D and oil before adding water. Keep the

emulsion agitated while spraying.

Grass and GrassUke Species

For most grass or grasslike species use amitrole

or dalapon. (See pp. 6, 10, and 55.) ^ Usually

the emersed aquatic weeds, especially in ditches

with running water, are less susceptible to soilsterilant herbicides than are ditchbank weeds.

Cattails and Bulrushes

Use the low-volatile ester formulation of 2,4-D

at 4 to 6 pounds in a 1 to 20 oil-water emulsion

and apply as a foliage spray. Use 150 to 300 gallons per acre. Make the first treatment just before heading stage of the weeds and repeat as

necessary on regrowth. About three applications

over a 2-year period are necessary for complete

control.

Apply dalapon at 15 to 30 pounds, acid equivalent, per acre in late summer or early autumn at

least 2 weeks before the first frost. Add oil at

the rate of 5 to 10 gallons per acre or add a good

wetting agent to the spray solution to improve

results. Repeat applications as necessary. For

spot spraying with spray gun, dissolve 10 pounds

in 100 gallons water and wet all foliage thoroughly.

Caution.—See precautions on pages 30, 37, and

46.

Apply amitrole at 6 to 12 pounds, active ingredient, per acre at the same time and in the same

way as dalapon.

The treatments with dalapon and amitrole are

more expensive than the 2,4-D treatment, but are

safer to use near crops extremely sensitive to

2,4-D. Use reasonable care, however, to prevent

herbicide treatments from drifting.

Dalapon-silvex mixture at 5 to 6 gallons per

acre, erbon at 40 pounds per acre, and fenuronTCA, emulsifiable, at 3 gallons (9 lb.) per acre

are promising for control of cattails.

WEED SPECIES AND HERBICIDES FOR CONTROL

This section consists of a table in which the

response of weeds to herbicides is given.

The weeds are listed in alphabetical order by

common names. Genus, species, and, in some instances, variety are given where response to herbicides is specific and information is available.

In the "Response to herbicides" column, S

means susceptible, I means intermediate, and R

means resistant. S and I represent ranges in response. The response of a plant to an application

of herbicide depends not only on the species but

also on the age of the plant, the rate of herbicide

used, and the soil and climatic environment in

which the plant is grown. Seedlings are killed

most easily—even seedlings of some resistant species are killed. Many plants become more tolerant to a herbicide as they grow older. Some

perennials are most easily killed when in bloom.

Woody plants may be more susceptible to one

method of application than to another. A weed

described as S to a herbicide may vary from a

susceptible reaction if treated at the optimum

time, with the optimum rate, and under the optimum environment to a more tolerant reaction under conditions less favorable for control. A weed

described as I may vary from tolerant to resistant; its response depends on age when treated,

rate of herbicide used, and environmental conditions.

When a weed is susceptible (S), it can be killed

with moderate rates of a herbicide. If it is intermediate in reaction (I), it is severely injured or

partially controlled by higher rates. If it is resistant (R), control with the herbicide is not

feasible.

The list of chemicals to which the response of

a weed species is listed as S or I or R is not complete. The absence of any chemical from the list

does not imply that it could not be used or that

it should not be used. Its absence means only

that it has not been tried sui&ciently or in direct

comparison with other chemicals by impartial investigators at this time (1963). Additions to the

list can be made when such information becomes

available.
AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 5.—Weed species and herbicides for control

[A, annual ; Aq, aquatic ; B, biennial ; P, perennial ; W, woody ; S, susceptible ; I, intermediate ; R, resistant ; pagination includes only those pages on which additional information is given]

Weed species

Absinthe (Artemisia absinthium)

African-rue {Peganum harmala)

Agrimony (Agrimonia gryposepala).

Alder :

(Alnus spp.)

black

speckled

tag

Alfilaria (Erodium cicutarium)

Algae

(Anahaena)

(Aphanizomenon)

(Chara spp.)

(Cladophora)

(Hydrodictyon)

(Lemna minor). (See Duckweed,

common.)

(Mycrocystis)

Growth

habit

A_

A_

P_

P_

W

W

w

w

Aor B_

Aq

Aq

Aq

Aq

Aq

Aq

Page

Response

to herbicide

S

R

I

R

Aq_

AqAq-

(Mougeotia) _.

( Oedogonium )

( Oscillâtoria) .

(Pithophora) .

(Spirogyra) _.

(Zygnema) __.

Alligatorweed (Alternanthera

philoxeroides).

Alyssum, hoary (Beteroa incana).

Amaranth :

green (Amaranthus hyhridus).

Palmer (A. palmeri)

Ammannia (Ammannia coccin-ea) —

Arrowgrass, seaside (Triglochin

m,aritima).

Arrowhead :

(Sagittaria calycina)

(S. longiloba)

Artichoke thistle (Cynara scolymus).

Ash (Fraxinus spp.)

Aspen (Populus spp.)

quaking (P. tremuloides).

Aster :

many-flowered (Aster ericoides).

western (A. occidentalis)

white heath (A. pilosus)

woody (Xylorrhiza parryi)

Aq_

Aq_

Aq_

Aq_

Aq_

Aq_

Aq_

Aq_

Aq_

Aq____

Aq.__.

Aq

Aq

BorP_

B or P_

A

A

AqAq_

Aq_

A.q_

Aq_

P__

P__

P__

W_.

W__

W_.

W_.

W_.

W_.

53,55

54, 56

54,56

54, 56

11, 54,

56

54, 56

54,56

54,56

54, 56

54

11, 54

11. 54.

50

54, 56

56"

Herbicide

S

R

S

S

S

R

S

R

S

54, 50

W_

P

P

P

P

7, 44, 45

45

S

S

S

I

Amitrole; li,4-D ; 2,3,6-TBA

Erbon

Silvex ; 2,4,5-T

2,4-D

AMS ; fenuron ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

Brush killer

Do.

2,4-D + TOA ; 2,4,5-T + TCA

DCPA

Copper sulfate ; dichlone ; diquat

Copper sulfate ; dichlone

Copper sulfate ; diquat

Dichlone ; endothall

Copper sulfate ; diquat ; endothall ; simazine ;

sodium arsenite

Dichlone ; monuron

Copper sulfate ; diquat ; endothall ; simazine ;

sodium arsenite

Dichlone, monuron

Copper sulfate ; dichlone

2,4-D

Copper sulfate ; sodium arsenite

Do.

Diquat

Dalapon

Endothall ; silvex ; simazine ; sodium arsenite

Copper sulfate

Copper sulfate ; endothall ; sodium arsenite

Copper sulfate ; sodium arsenite

Dichlone

Silvex ; 2,4-D

Amitrole ; MCPA

Amitrole ; 2,4,5-T

MCPA, 2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Do.

Do.

2,4-D ; 2,4,5-T

Diquat ; MCPA ; silvex ; 2.4-D ; 2,4,5-T

Endothall

Diquat ; silvex

MCPA ; 2,4-D

2,4,5-T

Fortified oil

:\ICPA

2.4-D ; 2,4,5-T

Amitrole ; fenac

AMS

Fenuron ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

AMS : fenuron ; 2,4-D ; 2,4,5-T

Amitrole ; 2,3,6-TBA

AMS ; fenuron : 2,4-D ; 2,4,5-T ; 2,4-D 4- TCA •

2,4,5-T 4- TCA

Amitrole ; 2,3,6-TBA

2,4-D

2,4-D ; 2,4,5-T

Silvex ; 2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T
HERBICIDE MANUAL 69

TABLE 5.—Weed speeies amd herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Baccharis. {See Coyotebrush.)

Bachelors-button {Centaurea cyanua).

BaUeya, desert {Baileya multiradiata).

BaUmustard {lifeslia paniculata)

Barberry :

AQegheny {Berheris canadensis)^.

Colorado {B,fendleri)

A—

P_-

A_-

S

S

Barley, wild {Hordeum juhatum) ^

Barnyard grass {Echinochloa

crus-galli).

Bassia, fivehook {Bassia hyssopifoUa).

Basswood {Tilia americana)

Bearberry {Arctostaphylos uvorursi),

Bedstraw :

cleavers {Qalium aparine)

smooth (G. mollugo).

Beech {Fagus spp.)

Beeplant, Rocky Mountain {Cleome

serrulata).

Beggarticks {Bidens frondosa and

B. vulgata).

Bellflower, creeping {Campanula

rapunculoides).

Bellwort {Colchicum autum/nale)

Bermudagrass {Cynodon dactylon)

Betony, Florida {Stachys floridoTia) —

Bindweed :

field {Convolvulus arvensis)

htdge (C. sepium)

Birch {Betula spp.)

Birdrape {Brassica rapa)

Biscuitroot {Lomatium leptocarpum)-

Bistort, American {Polygommi

histortoides).

Bittercress {Cardamine spp.)

Bitterweed or bitter sneezeweed

{Eelenium tenuifolium),

Blackberry {Rul)us spp.)

Black-eyed-susan {Rudhechia serótina)

Bladderwort {Utricularia spp.)

Blessedthistle {Cnicus henedictus)

Bloodweed {Ambrosia áptera)

Bluebells {Campanula rotundifoUa)—

W - -

W - -

w

W — -

A_ >

A -

A

51, 52,

55

A

W -

W

W

A

A_ - - .

P

P

S

R

S

R

S

Ww_

A__

R

I

R

S

R

S

R

S

R

I

P__

P__

P__

35-38,

49,55

P

P

34, 35,

50

P__

P__

WWB_.

P_.

P__

Aq...

A

A

W

W

W

P

Aq

Aq_

A_^

A__

P__

P__

36, 41,

45

56

sill"!-."

I

R

S

S

I

S

I

R

siiiiir""

R_

2,4-D

2,4-D ; 2,4,5-T

2,4-D

2,4,5-T

Simazine; 2,4-D

2,4-D

Simazine

Dalapon

Calcium and lead arsenate ; chlordane ; dalapon ;

DCPA ; DMPA ; TCA

MCPA ; silvei ; 2,4.D ; 2,4,5-T

2,4-D

Fenac

AMS ; 2,4,5-T

2,4-D

2,4,5-T

DNBP ; monuron ; silvex

MCPA ; sodium arsenite ; 2,4-D ; 2,4,5-T

Silvex

MCPA; 2,4-D; 2,4,5-T

AMS

2,4-D ; 2,4,5-T

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,3,6-TBA

MCPA ; 2,4-D

Dalapon ; herbicidal oils and fumigants

Amitrole ; BMM ; CBM ; CBMM ; diuron ;

monuron ; simazine ; TCA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

Dicamba ; fenac ; PBA ; sodium chlorate ;

2,3,6-TBA

CBM ; CBMM ; diuron ; MCPA ; monuron ;

silvex ; 2,4-D ; 2,4,5-T

Amitrole ; amitrole-T ; erbon ; simazine

MCPA; 2,4-D; 2,4,5-T

AMS ; fenuron ; 2,4,5-T

2,4-D

MCPA ;silvex ; 2,4-D ; 2,4,5-T

2,4,5-T

2,4-D

2,4-D ; 2,4,5-T

MCPA ; 2,4-D

AMS ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

TCA

AMS ; fenuron ; 2,4,5-T ; 2,3,6-TBA

Amitrole ; monuron ; silvex ; sodium chlorate

MCPA ; simazine ; 2,4-D

Silvex; 2,4-D; 2,4,5-T

Aromatic solvents ; erbon ; silvex ; sodium

arsenite ; 2,4,5-T

2,4-D

Do.

2,4-D ; 2,4,5^T

2,3,6-TBA

2,4-D
60 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Bluebur. {See Stickseed, or sticktight,

European.)

Bluegrass, annual {Poa annua)

Bluemustard {Chorispora tenella).

Bluestem, little {Andropogon

scopariua),

Bluethistle (Echium vulgäre)

Blueweed, Texas {Helianthus ciliaris).

Bouncing-bet (Saponaria offlcinalis)^-

Boxelder (Acer negundo)

Bracken {Pteridium aquilinum)

Brambles. (iSfee Blackberry.)

Briers. ( See Smilax. )

Bristlegrass :

bur {Setaria verticillata) .

knotroot {S. gemculata)

Bromegrass, downy {Bromus

tectorum).

Broomsedge {Andropogon virginicus)

Broomweed :

common {Outierrezia dracunculoides).

threadleaf {O. microcephala)

Buckbrush :

coralberry {Symphoricarpos

orhiculatus).

snowberry (S. ocddentalis)

Buckeye :

{Aesculus arguta)

California {A. califomica)

Buckhorn, Carolina {Rhamnus

caroliniana ).

Buckwheat :

tartary {Fagopyrum tartaricum).

wild. (iSfee Wildbuckwheat. )

Buffalo-bur {Solanum rostratum)

Bugleweed, creeping {Ajuga reptans)

Bullnettle {Cnidoscolus stimulosus)^

BuUthistle {Cirsium vulgäre)

Bulrush (ßfcirpws spp.)

Burdover {Medicago hispida)

Burcucumber {Sicyos angulatus) —

51,52

P

P

B

P

P

P

P

W

P

P

P

A__

P._

P-_

P._

P__

W_

W_

W_

W_

w_

w_

w_

w_

Ww_

WA__

A__

A__

A__

P__

P__

P__

B__

AqAqA__

A__

A__

44

35-37

55

~55

'55

41

41

36

7,56,

57

51

S—,

I_-.

R__

I-_.

R__

I

S-_.

I

R-.

R-_

S__.

S-_.

I

R__

R.

S_.

R_

S-_

R_

I__

R_.

I._

Calcium and lead arsenate ; chlordane ; DCPA ;

DMPA ; sodium arsenite

Silvex ; 2,4,5-T

2,4-D

MCPA

Fenuron ; 2,3,6-TBA

Silvex ; 2,4-D ; 2,4,5-T

MCPA ; 2,4-D ; 2,4,5-T

AMS ; amitrole ; fenuron ; 2,3,6-TBA

2,4-D

Silvex

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Fenuron ; silvex ; 2,4-D ; 2,4,5-T

CBM ; amitrole and AMS kill fronds

BDM ; BMM ; monuronTCA

Dalapon ; diuron ; erbon ; MCPA ; monuron ;

silvex ; sodium arsenite ; sodium chlorate ;

2,4-D

Amitrole ; dalapon ; diuron ; monuron ; TCA

Silvex ; 2,4-D ; 2,4,5-T

Amitrole ; dalapon ; diuron ; monuron ; TCA

Silvex ; 2,4-D ; 2,4,5-T

Amitrole ; dalapon ; diuron ; endothall ;

monuron ; simazine ; TCA

DCPA ; silvex ; 2,4-D ; 2,4,5-T

Dalapon

Silvex ; 2,4-D ; 2,4,5-T ; 2,3,6-TBA

Silvex ; 2,4-D ; 2,4,5-T

Do.

AMS ; fenuron ; 2,4-D

2,4,5-T; 2,3,6-TBA

Silvex

AMS ; fenuron

2,4-D ; 2,3,6-TBA

MCPA; silvex; 2,4,5-T

AMS ; MCPA

Silvex

2,4-D

Silvex ; 2,4,5-T

Fenuron

Dicamba ; endothall ; MCPA

Silvex ; 2,4,5-T

DMPA ; 2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

MCPA ; 2,4-D

2,4-D ; 2,4,5-T

MCPA ; simazine

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Amitrole ; dalapon ; MCPA ; silvex ; 2,4-D ;

2,4,5-T

Copper sulfate

Endothall ; silvex

MCPA ; 2,4,5-T

2,4-D
HERBICIDE MANUAL

TABLE 5.—IVeed species and herbicides for control—Continued

61

Weed species Growth

habit Page

Besponse

to herbicideHerbicide

Burdock :

common {Arctium minus)

great {A, lappa)

Bur-franseria {Franseria discolor)

Burhead {Echinodorus cordifolius)

Burnet {Poterium sanguisorba)

Burning-bush. {8ee Kochia,)

Burreed (8parganiumamericanum)

Burroweed {Haplopappus tenuisectus ).

Bush-honeysuckle (Diervilla lonicera).

Buttercup

bulbous {Ranunculus bulbous)

celeryleaf {R. scleratus)

corn {R. arvensis)

creeping {R. repens)

small-flower {R. abortivus)

taU {R. acris)

Butterweed {Senecio triangularis)

Buttonbush or buttonball {Cephalanthus occidentalis).

Cactus, pricklypear {Opuntia spp.)

Calendula {Calendula arvensis)

Camels-thorn {Alhagi camelorum)

Camphorweed {Heterotheca subaxillaris).

Campion :

bladder {8ilene cucubalus)

red {Lychnis dioica)

Canarygrass, Reed {Phalaris arundinacea).

Caragana or pea-tree {Caragana

arborescens).

Caraway {Carum carvi)

Carelessweed. {Bee Amaranth,

Palmer. )

Carpetgrass {Axonopus afflnus) —

Carpetweed {Mollugo vertidllata)

Carrot, wild {Daucus carota)

Cat.brier. {See Smilax.)

Catchfly :

hairy {Silène dichotoma)

nightflowering {S. noctiflora)

sleepy {S. antirrhina)

Catclaw, mimosa {Mimosa biuncifera).

Catnip {Nepeta cataria)

Cats-ear, spotted {Hypochaeris

radicata).

Cattail, broadleaf or common {Typha

latifolia) and narrowleaf {T.angustifolia ).

Ceanothus :

Jersey-tea {Ceanothus Americanus).

varnishleaf {C. velutinus var.

laevigatus),

wedgeJfeaf (0. cuneatus)

B

B

B

B

P

P

A

P

Aq_

Aq.

P

W

A, B, or P

P

A

A

P

34

54,56 S

I

S

54

50

R-.

I__.

S__

P

A or B

P

P

W

R_

S_.

Sw

A

P

P

A or B__

P

BorP_

P

P

W

W

B

B

A_.

W_

P__

AqAq_

WWW_

WW_

R_

I__

R_

I_-

7,36,

55

55

"35"

7,56,

57

R«

MCPA ; silvex ; 2,4-D ; 2,4,5-T

MonuronTCA

MCPA ; 2,4-D

Diuron ; monuron ; monuronTCA

Amitrole ; fenac ; PBA ; 2,3,6-TBA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

MCPA; 2,4-D

Endothall ; diuron ; monuron ; 2,4-D

Dalapon ; silvex

2,4-D ; 2,4,5-T

2,4-D

MCPA ; 2,4-D

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Monuron ; MCPA ; silvex ; sodium chlorate ;

2,4-D ; 2,4,5-T

Simazine

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

AMS ; 2,4-D ; 2,4,5-T

Silvex ; 2,4,5-T ; 2,3,6-TBA

DNC ; MCPA ; silvex ; 2,4-D

PBA ; 2,3,6-TBA ; 2,4,5-T

Sodium chlorate

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

Amitrole-T ; dalapon

Monuron ; simazine

Monuron ; 2,4,5-T

AMS ; diuron ; simazine

MCPA ; 2,4-D ; 2,4,5-T

Amitrole ; silvex

Amitrole

DCPA ; 2,4-D

Silvex ; 2,4,5-T

AMS

MCPA ; monuronTCA ; silvex ; 2,4-D ; 2,4,5-T

Diuron ; DNBP ; monuron

2,4-D

Dicamba ; DMPA ; endothall ; MCPA ; silvex ;

2,4-D ; 2,4,5-T

2,4-D

2,4,5-T

2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Amitrole ; dalapon ; 2,4-D esters

Amitrole-T ; erbon ; silvex ; 2,4,5-T

CBM ; CBMM

2,4,5-T

2,4-D

2,4-D ; 2,4,5-T

MCPA
62 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Oentipedegrass (Eremochloa

ophiuroides).

Chamise {Adenostoma fasciculatum).

Ohamomile :

corn (Anthemia arvensis)

stinking mayweed {A, cotula)

Chaparrel (Ceanothus spp.)

Charlock. (See Mustard, wild.)

Cheat or chess (Bromus secalinus)

Cherry (Prunus 8^^.)

Chestnut (Oastanea sp^.)

Chlckweed :

common (Stellaria media)

field (Cerastinim arvense)

mouse-ear (C, vulgatum)

Chicory (Cichorium intyhus)

Chinaberry (Sapindus drummondi) -

Chinquapin :

(Castanopsis sempervirens)

golden (0. chrysophylla)

Chittam (Bumelia lanuginosa)

Chokecherry. (See Cherry.)

ChoUa, jumping (Opuntia fulgida) «_

Cinquefoil :

blueleaf (Potentilla diversifolia)

common (P. canadensis)

rough (P. norvegica)

sulfur (P. recta)

Cleavers. {See Bedstraw, cleavers.)

Cockle, white (Lychnis alba)

Cocklebur, common (Xanthium

pennsylvanicum ).

Coffeebean (Sesbania exaltata)

Coffeeberry (Rhamnus californica)

Coffeetree (Gymnocladus dioica)

Coffeeweed :

(Cassia tora)

(Dauhentonia texana)

Coltsfoot (Tussilago fárfara)

Comfrey, common (Symphytum

offlcinale ).

Coneflower, tall (Rudheckia laciniata).

Coontail, common (Ceratophyllum

demersum).

55

W_

W_

AorB_

A

A_.

W_

A

W

W

W

W

W

41,43

R__

S__

I__.

2,51

A

A

P

P

P

P

P

P

P

W

W

w

w

w

w

w

p

p

p

A or B_

P

P

P__

P_-

A__

A__

A__

A__

A__

W_

W_

WA-_

A__

P__

P__

P__

P__

P__

Aq.

Aq51

43

35

54, 56

R__

S__

R__

S__

I-_.

R.

TCA

2,4-D ; 2,4,5-T

MCPA ; silvex

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

DNBP ; herbicidal oils

MCPA; 2,4-D; 2,4,5-T

DCPA ; silvex ; 2,4-D ; 2,4,5-T

AMS ; fenuron

Silvex ; 2,4,5-T ; 2,3,6-TBA

Amitrole ; 2,4-D

AMS ; fenuron

2,4,5-T

DCPA ; dicamba ; DNBP ; monuron ; silvex ;

sodium chlorate ; 2,4,5-T

2,4-D

Endothall ; MCPA

Silvex ; 2,4,5-T

2,4-D

MCPA

Dicamba ; silvex

2,4-D ; 2,4,5-T

DNBP ; endothall ; MCPA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Fenuron

2,4-D ; 2,4,5-T

Amitrole ; silvex ; 2,4-D ; 2,4,5-T

Silvex ; 2,4,5-T

Silvex ; TCA

2,4,5-T

2,3,6-TBA

2,4-D ; 2,4,5-T

2,4-D

MCPA ; silvex ; 2,4,5-T

2,4-D

2,4-D ; 2,4,5-T

MCPA ; silvex

Dicamba ; PBA ; 2,3,6-TBA

MCPA ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

MCPA ; monuronTCA

Diuron ; herbicidal oils ; monuron

MCPA ; silvex ; 2,4,5-T

2,4-D

Do.

AMS

2,4,5-T

MCPA ; 2,4-D

Silvex ; 2,4-D ; 2,4,5-T

Sodium chlorate

MCPA ; 2,4-D

Diuron ; monuron

MCPA; 2,4-D

Silvex ; 2,4-D ; 2,4,5-T

Aromatic solvents ; dichlone ; endothall ; silvex ;

simazine ; sodium arsenite ; 2,4-D ; 2,4,5-T :

2,3,6-TBA * '

Copper sulfate
HERBICIDE MANUAL 63

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Ooralberry. {Bee Buckbrush, coralberry.)

Coreopsis. {See Tickseed.)

Coriander {Bifora spp.)

Corncockle {Agrostemma githago)

Cornflower. {See Bachelors-button.)

Cotton, wild {HiUscus moscheutos) —

Cottonwood {Populus deltoides)

Cowcockle {Saponaria vaccaria)

Cowparsnip {Heracleum sphondylium).

Cowslip {Caltha palustris)

Coyotebrush {Baccharis pilularis)

CoyotiUo (Karwinskia JiumJ)oldtiana).

Crabgrass {Digitaria spp.)

Cranesbill. {See Geranium, Carolina.)

Creeping-Charlie. {See Ground-ivy.)

Creosotebush {Larrea tridentata)

Crotolaria, showy {Crotolaria specta-

'bilis).

Crotón :

Lindheimer {Crotón lindheimeri)-.

Texas (C. texensis)

woolly (0. capitatus)

Cudweed {Onaphalium spp.)

Currants (ßioesspp.)

Cutgrass {Leersia spp. )

Daisy:

English {Bellis perennis)

oxeye {Chrysanthemum leucanthemum).

Dallisgrass {Paspalum dilatatum)

Dandelion {Taraxacum officinale)

Dayflower {Commelina communis)

Deadnettle, red {Lamium purpureum).

Deathcamas :

foothiU {Zigadenus paniculatus) —

grassy (Z. gramineus)

Deerbrush {Ceanothus integerrimus) —

Deerweed {Lotus scoparius)

Desert-baileya. {See Baileya, desert.)

Desertparsley {Lomatium grayi)

Devilsclaw {Prohoscidea louisianica)^.

Dewberry. ( See Blackberry. )

Diapedlumordianthera {Justiciaspp.).

A

AorB_

W_.

W_.

W_.

W_-

A

P__

P-_

W-.

W_.

P-_

A-_

43,44

43

"5Î752

R_

WWA__

A__

A__

A_-

A^_

A__

W—

P

P

36,55-

P

P

P

P

P

P

P

P

35,55

33, 37,

50

P

P

A

A or B_.

P

P

P

P

W

W

A—

A-_

I__.

S_-

S—

R__

I__

R_.

S__

I__

S_-

I__

R_.

I->.

R_.

S_-

R__

S__

I—.

I__

R_.

S—

DNC

MCPA;2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

MonuronTCA

AMS ; 2,4-D

2,4,5-T

Amitrole

Dicamba ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

Herbicidal oil

MCPA; 2,4-D

2,4-D

2,4,5-T

Fenuron ; silvex ; 2,4,5-T

AMA ; calcium and lead arsenate ; chlordane ;

DCPA ; DMA ; DMPA ; PMA ; TCA

Silvex ; 2,4-D ; 2,4,5-T

Fenuron ; fenuronTCA

Monuron ; silvex ; 2,4-D ; 2,4,5-T ; 2,3,6-TBA

2,4-D

Do.

Silvex; 2,4,5-T

Silvex; 2,4-D; 2,4,5-T

Do.

2,4-D

AMS ; 2,4-D ; 2,4,5-T

Amitrole ; dalapon

Silvex ; TCA

MCPA ; 2,4-D

CBM ; CBMM

2,4,5-T

MCPA ; silvex ; 2,4-D

AMA ; dalapon

Diuron ; monuron

DMPA

MCPA ; silvex ; sodium chlorate ; 2,4-D ; 2,4,5-T ;

2,3,6-TBA

BMM ; CBMM

Amitrole ; DCPA ; diuron ; DMPA ; erbon

2,4-D

MCPA ; 2,4-D

2,4-D

2,4,5-T

2,4-D

Silvex

2,4-D

2,4-D ; 2,4,5-T

MCPA ;sUvex; 2,4-D

2,4-D

I Diquat
64 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 5.—Weed species cmd herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Dock:

broadleaf {Rumex ohtusifolius) _.

curly {R, crispus)

fiddle (Ä. pulcher)

smooth, or pale {R, altissimus)

veiny {R, venosus)

Dodder {Cuscuta spp.)

Dogbane. {See Indian hemp.)

spreading {Apocynum androsaemifolium).

Dogfennel :

{Eupatorium capillifolium)

yellow. {See Bitterweed or bitter

sneezeweed. )

Dogmustard {Erucastrum gallicum)

Dogwood :

{Gorrms spp.)

flowering (0. florida)

Dokewood. {See Oak, post.)

Ducksalad {Heteranthera limosa) _

Duckweed, common {Lemna minor)

Eelgrass. {See Wildcelery.)

Elderberry {Samhucus sp^,)

Elm:

{Ulmus spp.)

winged (17. alata)

Elodea. {See Waterweed.)

Eucalyptus {Eucalyptus spp.)

P__

P_-

P__

P__

P-_

P__

P__

P__

P__

35,36,

50

A-_

P.-

W

w

w

w

A

A

A

W

W

W

WW_

W_

WEuonymus {Euonymus fortune var.

vegetus).

Evening-primrose, common {Oenothera

tiennis).

False-chamomile. (See also Mayweed,

scentless. )

Falseflax (OameZwa spp.)

False-hellebore, California

( Veratrum californicum).

Fanweed. (iSfee Pennycress, field.)

Fanwort {Cahomha caroliniana)

Fennel, common or sweet {Foeniculum

vulgäre).

Fiddleneck, coast {Amsinckia intermedia).

Fieldcress, Austrian {Rorippa

austríaca).

Fieldmadder {Sherardia arvensis)

Filaree, redstem {Erodium cicutarium)

Fir:

balsam {Abies halsamea)

red {A. magnifica) _

white {A. concolor)

W_

W_

WW_

B_.

I-_

S—

I—

R_.

S__

S_-

I__.

s

s

53

41,47

41, 43,

47

45

36

A__

A__

P__

Aq_

AqP_.

A

AorB_

WW_

WW_

54

47

R

S

Silvex;2,4-D;2,4,5-T

MCPA

2,4-D ; 2,4,5-T

MCPA ; monuronTCA ; sodium chlorate

Silvex

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

Diuron ; monuron ; simazine

Herbicidal oils

MCPA ; süvex ; 2,4-D ; 2,4,5-T

2,4-D

Dicamba ; silvex ; 2,4-D ; 2,4,5-T

MCPA;2,4,-D

Fenuron

Silvex ; 2,4-D ; 2,4,5-T

A mitróle ; simazine

2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Copper sulfate ; diquat ; OCH ; sodium arsenite

Dichlone ; herbicidal oils ; silvex ; 2,4-D ; 2,4,5-T

AMS ; 2,4,5-T

2,4-D

Amitrole ; diuron ; fenuron ; monuron

AMS ; monuron

Silvex ; 2,4,5-T

Amitrole ; fenuron ; MCPA ; 2,4-D

Fenuron

AMS

Sodium arsenite

AMS ; diuron ; DNBP ; simazine ; TOA

Dalapon

SUvex ; 2,4-D ; 2,4,5-T

2,4-D

Amitrole ; 2,4-D

Dicamba ; DMPA

2,4-D

Silvex ; simazine ; sodium arsenite ; 2,4-D

Dichlone ; diquat ; endothall

DNBP ; herbicidal oils

Silvex ; 2,4-D ; 2,4,5-T

MCPA

Sodium arsenite

2,4-D

Do.

DCPA; 2,4-D

AMS

Amitrole ; 2,4-D

2,4-D

Do.
HERBICIDE MANUAL

TABLE 5.—Weed species and herbicides for control—Continued

65

Weed species

Fleabane:

annual {Erigeron annuus) ,

Oregon {E, speciosus)

rough or daisy (JE?. strigosus)

Flixweed {Descurainia sophia)

Florida-pusley {Riohardia scabra)

Flower-of-an-hour {Eibiscus trionum)

Foolsparsley {Aethusa cynapium)

Four-o'clock, wild {MiraUUs nyctaginea.)

Foxtail {Setaria spp.)

Franseria, woollyleaf {Franseria

tomentosa),

Frenchweed. {See Pennycress, field.)

Fumitory, common {Fumaria offlcinalis),

Galinsoga, hairy {Oalinsoga ciliata)

and smallflower (G. parvifiora),

Gallberry {Ilex glahra)

Garlic, wild {Allium vineale)

Geranium, Carolina {Geranium carolinianum).

Goatsbeard :

{Tragopogón duhius)

(T. pratensis)

common {T. porrifolius)

Goatsrue {Galega officinalis)

Goatweed. {See Crotón, Lindheimer.)

Golden-aster, false {Chrysopsis spp.)_

Goldenchain-tree {Laburnum anagyroides).

Goldenfleece {Haplopappus arborescens),

Goldenrod {SoUdago spp.)

Gooseberries :

{Ribes oxyacanthoides and

R. roezlii).

most other Ribes spp.

Goosefoot :

Jerusalem {Chenopodium botrys)-

nettleleaf {0, murale)

Growth

habit

A

A

P

A or B_.

A or B_.

A or B_.

A

A

A

oakleaf {G, glaucum) —

spear-leaved {Monolepis

nuttalUana),

Goosegrass {Eleusine indica)

Gooseweed {SpJienoclea zeylanica)

Gorse {TJlex europaeus)

Gourd, buffalo or wild {Cucúrbita

foetidissima).

Goutweed, bishops {Aegopodi/um

podograria).

A

P

P

A

A

A

A

A

W

P

P

P

A or B__

B or P

B

B or P

P

Page

51, 52,

55

Response

to herbicide

50,51

P

P

W

W

P

P

w

WA

A

A

A

A

A

A

A__

W_

W_

P_-

P__

P_.

37

S—

R_.

SR_.

SR_.

S_.

Herbicide

I—

R_.

I__

51,52

R

I

R

I

R

R_

R_

Silvex;2,4,5-T

MCPA;2,4-D

2,4-D

Silvex;2,4-D;2,4,5-T

2,4-D

MCPA

DCPA; 2,4-D

Herbicidal oils

MCPA; 2,4-D;2,4,5-T

Herbicidal oils

2,4-D

Erbon

AMA ; atrazine ; calcium and lead arsenate ;

chlordane ; dalapon ; DCPA ; simazine ; TCA

Silvex; 2,4-D ;2,4,5-T

Amitrole ; fenac ; 2,3,6-TBA

MCPA ; sUvex ; 2,4-D ; 2,4,5-T

DNC

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

DCPA

2,4,5-T

Dicamba ; methyl bromide ; SMDC ; 2,3,6-TBA

Dalapon ; fenac ; MH ; 2,4-D

Amitrole ; MCPA ; silvex ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

MCPA; 2,4-D

2,4-D

Do.

2,4-D ; 2,4,5-T

BMM

Simazine; TCA

Dalapon ; TCA

2,4-D

AMS

2,4-D

Do.

2,4,5-T

2,4-D

MCPA; 2,4-D; 2,4,5-T

Endothall

MCPA ;2,4.D; 2,4,5-T

Silvex

Endothall

MCPA ; 2,4-D

Calcium and lead arsenate ; chlordane ;

DCPA ; DMPA

Silvex; 2,4-D; 2,4,5-T

2,4-D ; 2,4,5-T

MCPA ; silvex

2,4-D ; 2,4,5-T

Sodium chlorate

Do.

2,4-D

Do.
66 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 5.—Weed species amd herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Grape-hyacinth {Muscari hotryoides)..

Greasewood {Sarcobatus vermiculatus)

Greenbrier {Smila^ hona-now) ^

P

w

. R

I

R~r-"vj

R

R.

I

MCPA

2,4-D

AMS

FenuronTCA

Amitrole ; MCPA ; monuron TOA ; si

2,4-D; 2,4,5-T; 2,3,6-TBA

2,4-D

DNC

2,4-D

MCPA

Silvex; 2,4,5-T

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Silvex; 2,4-D; 2,4,5-T

Monuron ; silvex

2,4-D; 2,4,5-T

MCPA

2,4.D ; 2,4,5-T

Monuron ; sodium chlorate

MCPA ; sUvex ; 2,4-D ; 2,4,5-T

Do.

2,4-D

2,4-D

Fenuron ; 2,4,5-T

AMS

Fenuron ; silvex ; 2,4,5-T

Amitrole ; 2,4-D

MCPA; 2,4-D

AMS ; fenuron ; 2,4,5-T

Amitrole

PBA;2.3,6-TBA

2,4-D

MCPA; silvex; 2,4,5-T

MCPA ; 2,4-D

2,4-D

Do.

CBM ; CBMM ; MCPA ; silvex ; 2,4-D

MCPA; 2,4-D

2,4-D

CBMM; MCPA; 2,4,5-T

2,4-D

MCPA; 2,4,5-T

AMS ; fenuron ; 2,4,5-T

Amitrole ; MCPA ; monuron ; montiro

silvex ; 2,4-D

2,4-D ; 2,4,5-T

Fenuron ; 2,4-D ; 2,4,5-T

Amitrole

2,4-D

MCPA; silvex; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Erbon

Sodium chlorate

Simazine ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

Amitrole

MCPA

2,4-D

W

w

W - - Ivex;

Gromwell :

common (Lithospermum

oißcinale).

com {L, arvense)

P

A

A

A R

Rvr."_v~

R

S

S

I

R

I

S . R

S

S

I

S

s

I

R

S

R

S

I

R

SI

I

R

S

T

R

I

R

I

Groundcherry :

clammy {Physalis heterophylla)

and purple-flower (P. lobata),

smooth (P. suholabrata'i

W _

W

W

Wrights (P. wrightii)

Ground-ivy (Olechoma hederacea)

Groundsel :

arrowleaf {Senecio triangularis)

common (8. vuloaris)

P

P

P

P

A __ «

A

cressleaf {8. glahellus) pnirm

p

Wridden {8. riddellii)

tansy-ragwort. (See Tansyragwort.)

threadleaf {8. longilobus)

Guava, common {Psidium guajava)

Gum, black {Nyssa sylvatica) w

W _ -

44

w

Gumweed (Qrindelia squarrosa) and

{O, perennis).

Hackberry {Celtis occidentalis)

p

w

w

Halogeton {Halogeton glomeratus)

A

A

Hares-ear-mustard {Coringia orientalis).

Hawkbit:

fall {Leontodón autumnalis)

rough {L. nudicatilis) -

A

P

P

A or B

P

P

P

Hawksbeard, smooth {Crépis capillaris)

Hawkweed :

mouse-ear {Hieracium pilosella)

orange (JT. aurantiacum)

2,4.5-T

yeUow {H. pratense) _ P

P

Hawthorn :

{Crataegus spp.) W

W

47

R_

I

I

R

S

R

S

I

nTiriA •

fleshy {C, succulenta) w

w

W - .

4l"

niuA;

Hazel {Corylus s^^.)

Heal-all {Prunella vulgaris) p> _

p

Hedgemustard {Sisymhrium officinale) ^ A

Heliotrope, wild {Heliotropium spp.) W

W R

R

S

S

Hemlock {Tsuga canadensis) « W

Hemp, wild {Cannabis sativa) A

Hempnettle {Galeopsis tetrahit) A

A I—

A R
HERBICIDE MANUAL 67

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Henbane, black {Hyoscyamus niger).

Henbit {Lamvum amplexicaule)

Hickory (Oari/a spp.)

Hoarycress. {See Whitetop.)

Hogpeanut {Amphicarpa hrdcteata)

Hogpotato {Hoffmanseggia densiflora)

Honeylocust {Oleditaia Macanthos) .

Honeysuckle {Lonicera spp.)

Hophombeam {Ostrya iHrginiana)

Hornwort {See Coontail, common.)

Horsebrush, Uttleleaf {Tetradymia

glahrata),

Horsenettle, Oarolina {Solanum carolinenae).

Horsetail, field {Equisetum arvense)^^

Horseweed, marestaU {Erigeron canadensis).

Houndstongue {Cynoglossum oMcinale)

Huisache {Acacia farnesiana)

Hydrangea, smooth {Hydrangea

arboresoens),

Indian hemp {Apocymim cannahinum)-

Indian mallow. {See Velvetleaf.)

Indian-rushpea. {See Hogpotato.)

Indian-tobacco {Lobelia inflata)

Indigo, curly {Aeschynomene virginica)

Iris, Rocky Mountain {Iris missouriensia).

Ironweed, western {Vemonia

haldwini),

Ironwood. {See Hophombeam.)

Ivy, English {Hederá helix)

Jerusalem-artichoke {HeUanthus

tuberosus).

Jewelweed {Impatiens pallida)

Jimmjrweed {Haplopappus pluriflorus).

Jimson-weed {Datura stramonium)

Johnsongrass {Sorghum halepense)

Jointvetch, northern. {See Indigo,

curly.)

A__

A__

W-.

W45

WR

S

RV-V-V"

s

I

R

P—

PP__

WWW.

WWWWw_

36,41

s..

R_.

I__

R_.

SI__

36

36,37

A__

A__

B-_

W_.

W-.

37

"35'

P—

P-_

P-.

I__.

A_-

A—

A__

P__

P__

P__

P__

A

P

A

A

P 35,38,

55

R2,4-D

Silvex

2,4,5-T

MCPA; 2,4-D

AMS

Amitrole ; fenuron ; fenurouTOA ; MOPA ;

monuron ; silvex ; 2,4,5-T

2,4-D ; 2,3,6-TBA

2,4-D

Fenac ; 2,3,6-TBA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

AMS ; 2,4,5-T

2,4-D

AMS ; amitrole ; fenac ; MCPA ; silvex ; TCA

Diuron ; DNBP ; simazine ; 2,4-D ; 2,4,5-T

AMS

2,4,5-T

Fenuron

2,4-D; 2,4,5-T

Amitrole

Atrazine ; simazine ; 2,4,5-T

MCPA ; 2,4-D ; 2,3,6-TBA

Atrazine ; 2,3,6-TBA

Amitrole ; BMM ; erbon ; MCPA ;

sodium chlorate

Diuron ; monuron ; monuronTCA ; silvex ;

2,4-D ; 2,4,5-T

Silvex ; 2,4,5-T

BMM ; MCPA ; 2,4-D

Diuron ; monuron ; monuronTCA ; 2,4-D

2,4-D; 2,4,5-T

2,4-D

Atrazine

2,4-D

Amitrole; MCPA; 2,4,5-T

2,4-D

2,4,5-T

MCPA; silvex; 2,4-D

2,4-D

Silvex ; 2,4,5-T

Amitrole ; 2,4-D ; 2,4,5-T

Silvex

2,4,5-T

2,4-D

2,4-D; 2,4,5-T

2,4-D

2,4-D ; 2,4,5-T

MCPA; 2,4-D; 2,4,5-T

DCPA

BMM ; CBM ; dalapon ; herbicidal oüs ;

sodium chlorate ; TCA

CBMM ; erbon ; fenac ; monuron ; monuronTCA ;

2,3,6-TBA

Amitrole ; amitrole-T ; MH ; silvex ; simazine ;

2,4-D ; 2,4,5-T
68 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 5.—Weed species omd Therbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Juniper :

iJurUperus spp.) {See also Redcedar, eastern.)

(J. horizontalis ^plumosa')

Kidneywort baccharis. (See Ooyotebnish.)

Kikuyngrass {Permisetum clandestinum).

Kinghead. (See Ragweed, giant.)

EQamath-weed. {See St.-Johns-wort.)

Knapweed :

black (Centaurea nigra)

brown (O. jacea)

diffuse ((7. diffusa)

Russian (C repens)

spotted (0. maculosa)

squarrose (C squarrosa)

Knawel, annual {Scleranthus annuus).

Knotweed ;

Japanese. {See Smartweed,

Japanese.)

prostrate {Polygonum aviculare).

Sakhalin (P. sachalinense)

silversheath (P. argyrocoleon)

Kochia {Kochia scoparia)

Kudzu {Pueraria lobata)

Ladysmantle {Alchemilla arvensis)

Ladysthumb. {See Smartweed, ladysthumb.)

Lambsquarters, common {Chenopodium

album, )

Lantana {Lantana cantara)

Larch {Larix spp.)

Larkspur :

duncecap {Delphinium occidentale).

little {D. bicolor)

menziesii (Z>. menziesii)

tall {D. barheyi)

Leatherwood (Dirca palustris)

Leptotaenia, carrotleaf {Leptotaenda

multifida).

Lettuce :

blue {Lactuca pulchella)

prickly or wild {L. scariola)

Licorice, wild {Qlycyrrhiza lepidota)^.

Lilac {Syringa vulgaris)

Linden. (See Basswood.)

Ww_

WW36,45

36, 37,

55

P__

P-_

B-_

B__

P_- 34,37

A— 51

A__

A__

P__

A__

A__

A__

P__

P__

P__

A-_

A_.

W_.

W_.

W_.

P__

P__

P__

P__

P__

P__

P__

WP__

P>_

36

I—

R_.

R_.

I__

SI__

P__

A__

P-_

WR

S

S

I

S

siiiV-ir

Amitrole ; diuron ; fenuron ; monuron ; 2,3,6-TBA

AMS ; simazine

Silvex;2,4-D;2,4,5-T

Simazine

CBM ; erbon

Dalapon ; sodium chlorate ; TCA

Amitrole

2,4-D

Do.

Do.

MCPA ; silvex ; 2,4,5-T

AMS ; BDM ; CBM ; erbon ; fenac ; PBA ;

sodium chlorate ; 2,3,6-TBA

BMM ; CBMM

Amitrole ; amitrole-T ; MCPA ; silvex ; simazine ;

2,4-D ; 2,4,5-T

MCPA ; silvex

2,4-D ; 2,4,5-T

2,4-D

Silvex

MCPA ; 2,4-D ; 2,4,5-T

Dicamba ; DMPA ; DNBP ; monuron ;

sodium chlorate

Silvex ; 2,4-D ; 2,4,5-T

MCPA ; sodium arsenite

2,4-D

Do.

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Erbon ; sodium chlorate

MCPA ; sUvex ; 2,4-D ; 2,4,5-T

DNC

MCPA; 2,4-D

DCPA ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

EndothaU

BMM ; CBMM ; fenuron

MonuronTCA

2,4-D ; 2,4,5-T

Silvex ; 2,4,5-T

MCPA; 2,4-D

Silvex; 2,4-D; 2,4,5-T

2,4-D ; 2,4,5-T

Silvex plus 2,4,5-T

Fenuron ; silvex ; TCA

Amitrole ; MCPA ; 2,4-D ; 2,4,5-T

2,4-D

2,4,5-T

2,4-D

MCPA ; sUvex ; 2,4-D ; 2,4,5-T

Atrazine ; BMM ; MCPA ; 2,4-D

CBMM ; 2,4-D

2,4,5-T
HERBICIDE MANUAL

TABLE 5.—Weed species and herbicides for control—Continued

69

Weed species Growth

habit Page to herbicide

Herbicide

Locoweed :

bigbend {Astragalus earlei)

white. {See White-locoweed. )

Locust, black {Robinia pseudoacada)^.

Loosestrife :

purple or spiked {Lythrum

salicaria),

swamp. {See Swamp-loosestrife.)

Lotebush or lotewood {Condalia

ohtusifolia),

Lotus, American {Nelumho lutea)

Lupine :

{Lupimis rivularis)

silvery {L, argenteus)

tailcup {L, caudatus)

Madrone {Arbutus menziesii)

Magnolia {Magnolia spp,)

Maidencane {Panicum hemitomon)

Mallow :

alkali {See Sida, alkaU.)

common or cheese {Malva

neglecta).

dwarf or roundleaf {M. rotwndifolia).

Indian. {See Velvetleaf.)

little {M. parviflora)

Venice. {See Flower-of-an-hour.)

Mannagrass, water. {See Sweetgrass,

floating.)

Manzanita :

{Arctostaphylos spp. )

greenleaf {A,

Maple :

{Acer spp.) .

columbiana)

Norway {A, plantanoides)

Marestail. {See Horseweed, marestaU.)

Marigold, corn {Chrysanthemum

segetum).

Marsh-elder {Iva xanthifolia)

Mayweed:

scentless {Matricaria maritima

inodora).

stinking. {See CJhamomile, stinking mayweed.)

Meadowsweet. {See Spirea.)

Medic, black {Medicago lupulina)

Medusahead {Elymus caput-medusae)

Mercury, annual {Mercurialis amiua).

Mescalbean. {See Norcalbean.)

A or P

WW7,

45-47

S

AqAqWAqAq56

W

P

P

P

P

W

W

Aq

Aq

Aq

AorB,

R_

WW_

w.

w_

w_

w_

W36,

44-47

A

A

A

A_-

A__

A

A

Á

A

A

A

S-_

R_.

S—

Il_-

2,4-D

Amitrole ; fenuron ; sllvex ; 2,3,6-TBA ; 2,4,5-T

AMS ; monuron ; 2,4-D

Silvex

2,4.D

2,4-D ; 2,4,5-T

AMS ; silvex ; 2,4-D ; 2,4,5-T

Dalapon

2,4-D; 2,4,5-T

Silvex ; 2,4,5-T

2,4-D

MCPA

2,4-D

2,4-D ; 2,4,5-T

2,4,5-T

Dalapon

Monuron ; TOA

Amitrole ; BMM ; 2,3,6-TBA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

DNBP ; herbicidal oils

2,4-D

MCPA

Silvex ; 2,4-D ; 2,4,5-T

MCPA

2,4-D; 2,4,5-T

AMS ; fenac ; silvex

Diuron ; DNBP ; fenuron ; simazine ; 2,4,5-T

Amitrole ; MCPA ; 2,4-D

Dalapon ; TCA

DNC

MCPA ; 2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Amitrole ; sodium chlorate

MCPA;2,4.D

Silvex

MCPA; 2,4-D; 2,4,5-T

Dalapon ; simazine

Silvex; 2,4-D; 2,4,5-T

DNC

MCPA; 2,4-D
70 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE ö.—"Weed species cmd herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Mesquite

honey {Prosopis juliflora var.

fflandulosa).

velvet (P. juUflora var. velutina)

Mexican-fireweed. ( See Kochia. )

Mexican-tea {Ohenopodium ambrosioides).

Mexican-weed {Caperonia castaneaefolia).

Milkvetch :

{Astralagus spp.)

narrowleaf {A, pectinatus)

W_

WWWWW_

W_

43,45

two-grooved {A, l)isuloatus)

Milkweed:

bloodflower {Asclepias curassavica),

broad-leaved {A. latifoUa)

climbing {Ampelanus alhidus)

common {Asclepias syriaca)

showy {A, speciosa)

western whorled {A, verticillata) ^

MiUet, Texas {Panicum texanum)

Mint:

field {Mentha arvensis)

water {M, aquatica)

Mockorange {Philadelphus virginalis).

Moneywort {Lysimachia nummularia),

Monolepls. {See Goosefoot, spearleaved.)

Morning-glory (/pomoea spp.)

A__

A__

P__

P__

P__

P__

P

51,52

Mountain-mahogany {Gercocarpus

montarms).

Mountain-misery {Chamaébatia

foliolosa).

Mugwort {Artemisia vulgaris)

P

Aq

W

P

A

A

W

36

36

W_

Mulberry {Morus spp.)

Mulesears {Wyethia amplexicaulis)

Mullein :

common {VerJyascum thapsus)

moth {V, hlattaria)

Muskgrass. {See Algae, Chara spp. )

Mustard :

black {Brassica nigra)

P

P

W

W

W

P

B

B

P

35

Indian {B. júncea)

white {B, flirta)

wild {B. kaher)

A_.

A__

A__

A._

A..

A__

S

S

R

R

I

S

S

I

R

I

R

S

R~_~_~_'_'~_"

S

I

R

I

Fenuron

Silvex ; 2,4,5-T

Amitrole ; 2,4-D ; 2,3,6-TBA

Fenuron

Silvex; 2,4,5-T

MCPA ; 2,4-D

MCPA ; sUvex ; 2,4-D ; 2,4,5-T

Silvex; 2,4,5-T

MCPA ; 2,4-D

Silvex ;2,4.D; 2,4,5-T

MCPA

Silvex

2,4-D ; 2,4,5-T

2,4-D

2,4-D ; 2,4,5-T

Amitrole

Amitrole ; silvex ; 2,4-D

Erbon ; PBA ; 2,3,6-TBA

2,4-D

Amitrole ; silvex

Erbon ; herbicidal oils ; MCPA ; simazine ;

2,4-D ; 2,4,5-T

Silvex

Amitrole

MCPA ; 2,4-D ; 2,4,5-T

Amitrole

MCPA ; 2,4-D ; 2,4,5-T

Chlordane ; DCPA ; DMPA ; lead and calcium

arsenate

2,4-D

MCPA ; 2,4-D

Dalapon ; diuron ; DNBP ; simazine ; TCA

2,4-D

Silvex ; 2,4-D ; 2,4,5-T

Sodium chlorate

2,4,5-T

2,4-D ; 2,4,5-T

Monuron ; monuronTCA

MCPA ; 2,4-D ; 2,4,5-T

Fenuron

Silvex

Amitrole ; 2,4-D ; 2,4,5-T

Silvex ; 2,4-D ; 2,4,5-T

2,4,5-T

MCPA;2,4.D

2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4.D ; 2,4,5-T

DCPA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

DCPA ; endothan
HERBICIDE MANUAL 71

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page:

Response

to herbicide

Herbicide

Naiad:

{Najas gracillima)

southern {N, guadalupensis) _

INatalgrass (Tricholaena rosea) __

Needle-and-thread {Stipa comata)

¡Needlerush {Juncus roemerianus)

Nettie:

burning {Urtica urens)

stinging (17. dioica)

taU (17. procera)

Nlggerhead {Rudheckia occidentalis)^.

Nightshade :

black or purple {Solanum nigrum)

Aq_

AQ53,54

55,56

P

P

Aq

Aq

Aq_

cutieaf (Ä. triflorum)

silverleaf (fif. elaeagnifolium)

Nlmblewill {MuMenbergia sohreberi).

Norcalbean {Sophora secundifiora)

Nutgrass, or nutsedge :

purple {Cyperus rotundus)

yellow (C. esculentus)

Oak:

black {Quercus velutina)

blackjack (Q. marilandica)

bluejack (Q. douglasii)

canyon live (Q. chrysolenpis)

gambel (Q. gambelii)

interior live {Q. wislizenii)

live (Q. virginiana)

Oregon (Q. garryana)

post (Q. stellata)

red (Q. rubra, Q. coccínea,

Q. ellipsoidalis),

scrub {Q. dumosa)

shinnery (Q, havardii)

turbinella (Q. turhinella)

Turkey (Q. laevis)

white (Q. alba)

A__

P__

A__

A__

A__

P

P 51,52

W_

P

P

P

37,49,

51

36,49,

51

W_

WWW_

W_

W_

WW_

WWW_

W_

W_

WW_

WW_

W_

WW_

W_

W_

w_

w_

WWw_

WWw_

43,45

43,45

43,45

43

~43

43,45

~4~374~5

R

S

R

R

S

I

R

S

S

s

s

s

I

R

I

R

S

R

s:

s

I

R

S

I

R

I

R

I

R

S

I

R

R

I

R

I

I

S

I

R

S

I

R

I

R

S

I

R

R

S

I

R

S

I

R

Diquat ; endothall

Acrolein ; aromatic solvents ; dichlone ; diquat ;

sodium arsenite

BMM ; CBMM

Silvex ; 2,4-D ; 2,4,5-T

Diuron ; monuron ; silvex ; 2,4-D

Dalapon

Erbon

2,4-D

MCPA ; monuron ; 2,4-D ; sodium chlorate

Monuron ; 2,4-D

2,4-D

Silvex

MCPA ; 2,4-D ; 2,4,5-T

CBMM

2,4-D

Fenac ; silvex ; 2,4-D ; 2,4,5-T ; 2,3,6-TBA

Calcium and lead arsenate ; chlordane ;

DCPA;DMPA

Amitrole ; diuron ; monuron ; monurouTOA ;

2,4-D ; 2,4,5-T

Süvex ; 2,4,5-T

Chloropicrin ; methyl bromide

BMM ; 2,4-D

Amitrole ; CBMM ; DMTT ; erbon ; MCPA ;

monuron ; silvex ; simazine ; TCA ; 2,4,5-T

Chloropicrin ; methyl bromide ; TCA

A-lrazine * 2 4-l~)

CBMM; MCPA; MH; silvex; simazine; 2,4,5-T

2,4,5-T

2,4-D

Silvex; 2,4,5-T

MCPA; 2,4-D

Fenuron

Silvex ; 2,4,5-T

MCPA ; 2,4-D ; 2,3,6-TBA

2,4-D ; 2,4,5-T

2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T ; 2,3,6-TBA

2,4,5-T

2,4-D ; 2,4,5-T

AMS ; fenuron ; silvex ; 2,4,5-T

2,4-D

MCPA ; 2,3,6-TBA

AMS ; monuron

2,4,5-T

Amitrole

Silvex ; 2,4,5-T

MCPA ; 2,4-D

Silvex ; 2,4,5-T

2,4-D

Amitrole ; 2,3,6-TBA

2,4,5-T

Diuron ; monuron ; silvex

Fenuron ; 2,4-D ; 2,4,5-T

Amitrole ; AMS ; 2,3,6-TBA

AMS ; monuron ; 2,4,5-T

Silvex ; 2,4-D

Amitrole ; MCPA
72 AGRICULTURE HANDBOOK 269, U.S. DEPT. OP AGRICULTURE

TABLE 5.—Weed species amd herbicides for control—Continued

Weed species

Oats, wild {Avena fatua and A, ludovioiana).

Onion :

tapertip {Allium acummatum)

wild (A. canadense)

Orache {Atriplex patula var. hastata).

Osage-orange {Madura pomífera)

Oxalis. {See Woodsorrel, yellow.)

Pagodatree {Sophora japónica)

Palmetto, saw {Berenoa repens)

Panicum {Pwnicum spp.)

faU (P. dichotomiflorum)

Paragrass {Panicum purpurascens)

Parrotfeather {Myriophyllum

hrasilense).

Parsnip, wild {Pastinaca sativa)

Partridgepea {Cassia fasciculata)

Paspalum (PaspaZi¿m spp.)

Passionflower, maypop {Passiflora

incarnata).

Pea, wild {Lathyrus aphaca)

Pea-tree. {See Caragana or pea-tree.)

Peavine {Astragalus emoryanus)

Pecan {Garya ilUnoensis)

Pellitoryweed {Parietaria floridana) _.

Pennycress, field {Thlaspi arvense)

Pennywort :

lawn {Eydrocotyle sidthorpioides).

water {H. umhellata)

Pentstemon, Rydberg {Pentstemon

rydbergii).

Pepperweed, or peppergrass :

clasping {Lepidium perfoliatum)-.

field {L, campestre)

greenflower {L, densiflorum)

perennial {L, latifoUum)

Virginia {L. virginicum)

yeUowflower (Z/. perfoliatum)

Growth

habit

P

P

P

P

A

A

W

W

w

w

w

w

w

p

Aq_

Aq_

AQAq_

B__

A__

P_-

P__.

P__.

W

W

A

A

A

P

Aq

P

P

A

A

P

P

A

A

Page

50,51

36,37,

51,55

51,52

36,55

54,56

51, 52,

55

45

50,53

Response

to herbicide

R_.

S_.

I__

R_.

I-_

S__

S__

s__

I__.

R-_

S

S

R

S

R

S

Herbicide

Atrazine ; dalapon ; diuron ; monuron ; simazine ;

sodium arsenite

DCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

Dicamba ; methyl bromide ; SMDO ; 2,3,6-TBA

2,4-D

Amitrole ; dalapon ; MCPA ; MH ; 2,4,5-T

2,4-D ; 2,4,5-T

Endothall ; sodium arsenite

AMS ; 2,4,5-T

Fenuron ; silvex

2,4-D

Dalapon ; TCA

Silvex

2,4,5-T

Monuron

Calcium and lead arsenate ; chlordane ;

DCPA ; DMPA

Atrazine ; BMM ; dalapon ; monuron ;

simazîne ; TCA

CBMM ; 2,4-D ; 2,3,6-TBA

Calcium and lead arsenate ; chlordane ;

DCPA; DMPA

Dalapon ; monuron ; simazine

TCA

Dichlone ; emulsifiable solvents ; endothaU ;

monuron ; silvex ; 2,3,6-TBA

2,4-D

2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Amitrole ; dalapon ; DMA

Fenuron ; 2,3,6-TBA

Diuron ; monuron ; monuronTCA ; silvex ;

sodium arsenite ; 2,4-D ; 2,4,5-T

Silvex

2,4-D

DNC; MCPA; 2,4-D

2,4-D ; 2,4,5-T

AMS

Fenuron

2,4,5-T

MCPA; 2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Silvex ; MCPA ; 2,4-D ; 2,4,5-T

2,4-D

Do.

2,4,5-T

MCPA ; süvex ; 2,4-D ; 2,4,5-T

Calcium and lead arsenate ; MCPA ; 2,4-D :

2,4,5-T

Silvex

2,4-D

MCPA

2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Do.
HERBICIDE MANUAL

TABLE 5.—Weed species and herbicides for control—Continued

73

Weed species

Persimmon :

common (Diospyros virgimana) __

Texas (D. texana)

Phragmites {Phragmites communis) —

Pickerelweed {Pontederia cordata)

Pigweed :

prostrate (Amaranthus graecizans)

redroot or rough {A. retroflexus)

smooth (A. hyhridus)

spiny {A, spinosus)

tumble (A. alhus)

Growth

habit

W

W

W

W

Aq

Aq

Aq

Â

Pimpernel, scarlet {AnagalUa arvense).

Plncherry {Prunus pennsylvanicum)..

Pine:

jack {Pin/U8 hanJcsiana)

Jeffrey (P. jeffreyi)

lodgepole (P. contorta)

red (P. resin^osa)

white (P. atro^us)

Pineappleweed :

{Matricaria chamomilla)

{M. matricarioides)

Pingue. (See Rubberweed, Colorado.)

Plantain —

blackseed {Plantago rugelii)

bracted (P. aristata)

common or broad-leaved

{P. major).

English or buckhom

(P. lanceolata).

slender (P. pusilla)

wooUy (P. purshii)

Plum

A

A

A

A__

W_

WWWw>

WWWw_

WWPage

41,43,

45,47

56

"Be"

"51"

Response

to herbicide

S

I

R

S

S

I

S

43

A__

A._

chickasaw (Prunus angustifolia)-

wild. {See Cherry.)

Poison-hemlock ( Conium maculatum ).

Poison-ivy {Rhus radicans)

Poison-oak {Rhus diver8îloJ)a)

Poison-sumac {Rhus vernix)

Pokeweed {Phytolocca americana) —

A or P

P

A

P

47

43

WW_

W_

WB_-

B__

B_-

WW_

WWWWP

P

33

50

~5Ô'

50

S—

S_-

s__

Herbicide

S_.

R_

R_

I__

R_

S_.

R_

S_.

I_.

R_

R_

I_-

R_

44

7,47,

48

S

S

S

7,47,

48

7,47,

48

S

I

AMS ; fenuron ; 2,3,6-TBA

Amitrole ; monuron ; silvex ; 2,4,5-T

2,4-D

Silvex ; monuron ; 2,4-D

Amitrole ; dalapon

Amitrole-T ; monuron

Silvex; 2,4-D; 2,4,5-T

Atrazine ; silvex ; 2,4-D ; 2,4,5-T

Atrazine ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Silvex ; 2,4-D ; 2,4,5-T

Atrazine ; dicamba ; MCPA ; silvex ; 2,4-D ;

2,4,5-T

DNC

MCPA ; 2,4-D

2,4-D

Dalapon ; TCA

2,4-D ; 2,4,5-T

Do.

2,4,5-T

2,4-D

Amitrole

2,4-D ; 2,4,5-T

Dalapon ; TCA

2,3,6-TBA

Amitrole ; simazine ; 2,4-D ; 2,4,5-T

DNBP; MCPA; 2,4-D

2,4-D

DNBP ; herbicidal oils ; MCPA ; silvex ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Do.

2,4-D

Do.

AMS ; fenuron

2,4,5-T ; 2,3,6-TBA

Amitrole ; silvex ; 2,4-D

MCPA; silvex; 2,4-D

2,4,5-T

Herbicidal oils

Amitrole ; AMS ; brush killer ; fenuron ; silvex ;

2,4,5-T

MCPA ; 2,4-D

Amitrole ; AMS ; brush killer ; silvex ; 2,4,5-T

2,4-D

MCPA ; monuronTCA ; sodium chlorate

Amitrole ; AMS ; brush kiUer ; 2,4,5-T

Silvex ;2.4,5-T

MCPA; 2,4-D
74 AGRICULTURE HAJSTDBOOK 269, U.S. DBPT. OF AGRICULTURE

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Pondweed :

{Potamogetón s'ov.)

honied (Zarmichellia palustris) .

leafy (Potamogetón foliosus)

sago {P. pectinatus)

Ponyfoot {Dichondra repens)

Poolmat, common. {See Pondweed,

horned.)

Poorjoe {Diodia teres)

Poplar, or popple :

{Populus tremuloides),

Aspen, quaking.)

balsam (P. balsamifera)

Poppy:

{Papaver spp.)

{8ee

Roemer {Roemeria refracta)

Povertyweed {Iva axillaris)

Prairiegrass. {See Rescuegrass.)

Pricklepoppy {Argemone intermedia)

Prickly-ash, northern {Zanthoxylum

americanum).

Primrose-willow {Jussiaea peruviana),

Puncturevine {Trihulus terrestris)

Purslane, common {Portulaca olerácea)

Quackgrass {Agropyron repens)

Queensdelight {Stillingia sylvatica)

Rabbitbrush, grey {Chrysothamnus

nauseosus) and yellow {Cviscidiflorus).

Radish, wild {Raphanus raphanistrum)

Ragweed :

common {Ambrosia artemisiifolia)-

giant (A, trífida)

western {A. psilostacfiya)

Ragwort, golden {Senecio aureus)

Rape, wild {Rapistrum rugosum)

Raspberry, wild black or red.

Blackberry. )

Redbay {Persea horbonia)

Redbud {Gercis canadensis and

O, occidentalis),

Redcedar, eastern {Juniperus

virginiana).

Redstem {Ammannia coccínea)

Aq 53-55

Aq_

Aq. 54

Aq_

AqAqAq_

Aq.

P...

54

54

51

A__

WA

A

A

P

P

S

R

S

S

I

A_.

WWAqA._

A__

A._

56

34

A

P 7,35,

37,55

P-_

P..

W_.

WA S

R

A

A

A

P

P

A or B

W—

W—

W—.

W__.

w__.

W—

w__.

A

35

43

S

R

S

S

I

s

41

Acrolein ; aromatic solvents ; dichlone ;

endothall ; silvex ; sodium arsenite

2,4-D

Aromatic solvents ; dichlone ; endothall ;

monuron ; slmazine ; sodium arsenite

Copper sulfate

Diquat

Acrolein ; diquat ; simazine ; sodium arsenite

2,4-D

Copper sulfate

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

MCPA ; silvex

2,4-D

DNC

MCPA ; 2,4-D

2,4-D

2,4-D

PBA ; 2,3,6-TBA

2,4-D

2,4,5-T

2,4-D

Diuron ; monuron ; silvex ; 2,4-D ; 2,4,5-T

Fenac ; 2,4-D

MCPA ; silvex ; 2,4,5-T

DCPA ; silvex ; 2,4,5-T

Dicamba ; 2,4-D

BMM ; DMPA ; endothaU ; erbon ; MCPA

Atrazine ; amitrole-T ; monuron ; simazine ;

sodium chlorate ; TCA

Amitrole ; CBM ; CBMM ; dalapon ; erbon ;

fenac ; MH ; monuronTCA

BDM ; DMPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

Do.

MCPA; silvex; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Endothall

BMM ; MCPA ; sUvex ; 2,4-D ; 2,4,5-T

DCPA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

AMS ; silvex ; 2,4-D ; 2,4,5-T

Diuron ; monuron ; monuronTCA

DNC; MCPA; 2,4-D

2,4,5-T

Silvex ; 2,4-D

AMS ; silvex

Fenuron

2,4-D ; 2,4,5-T

Diuron ; fenuron ; monuron

AMS ; amitrole ; 2,4-D ; 2,4,5-T ; 2,3,6-TBA

MCPA ; silvex ; 2,4-D ; 2,4,5-T
HERBICIDE MANUAL 75

TABLE 5.—Weed species cmd herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Redtop {Agrostis spp.) A or P

A or P___

AorP

37,55 S

I

R

R

I

S

R

R

S

Amitrole ; diuron ; methyl bromide ; monuron

Dalapon

2,4-D ; 2,4,5-T

Herbicidal oils ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

Monuron

Sodium chlorate ; 2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Do.

Redvine {Brunnichia cirrhosa)

Redwood {ßequoia sempervirens)

Reed, common or giant. {8ee Phragmites. )

Rescuegrass (Bromus catharticus)

P

W

A or B___

Aor B

Rocket :

London {Franseria confertiflora ) __

London {Sisymbrium trio)

Rose - -

P

A

W

W

W

W

W

w

w

45"

California {Rosa californica)

Cherokee (R. laeviaata)

I

R

S

I

I

R

S

I

R

S

I

R

I

R

S

S

I

S

I

s

s

s

s

s

I

I

s

s

2,4,5-T

2,4-D

Monuron ; silvex

Macartney {R. hracteata)

2,4-D ; 2,4,5-T

Silvex ; 2,4-D ; 2,4,5-T

MCPA

multiflora {R. multiflora) w

w

w _

_____'_'_

Monuron ; 2,3,6-TBA

Silvex ; 2,4,5-T

MCPA ; simazine ; 2,4-D

nrairie (R nratiticola) w

w

w _

41 2,4,5-T

2,4-D

BMM

Woods {R. woodsii) w

w _

2.4,5-T

Silvex ; 2,4-D

Rubberweed :

bitter {Hymenoxys odorata)

Colorado {H. richardsonii)

Rush:

(Juncus SDD. )

A

p

p

Aq

Aq

P

A

56

2,4-D

Do.

PBA ; 2,4,5-T ; 2,3,6-TBA

Amitrole ; atrazine ; dalapon ; diuron ;

slender (J. tenuis)

Russian-pigweed {Axyris amaranthoides).

Rnc?<?ifln-thistlp (Salsola kali)

monuron ; silvex ; sodium chlorate ; 2,4-D

Amitrole-T ; MCPA

2,4-D

Do.

A 34 Dicamba; fenac; MCPA; silvex; 2,4-D; 2,4,5-T

"Rvperrn«?«? ( TjOliutti SüD ) A or P

P

P

P

P

P

Dalapon

2,4-D ; 2,4,5-T

MCPA ; silvex

MCPA ; 2,4-D

Sage:

creeping {Salvia sonomensis)

meadow (8. vratensis)

purple {8, leucophylla)

whîfp (S aoiana)

2,4-D

Do.

Sagebrush - W

W

W

W

r.i

big {Artemisia tridentata) s

I

R

s

I

s

I

s

I

R

I

S

R

2.4-D ; 2,4,5-T

Silvex

MCPA

California {A. calfornica)

frinerpd (A iriaida)

w 2,4-D ; 2,4,5-T

w

w

w

p - .

43'

2,4-D

sand (A fUifolia) MCPA ; silvex ; 2,4-D ; 2,4,5-1^

^ilvpr (A cana) 2,4-D

St.-Johns-wort :

Klamath-weed {Hypericum

perforatum).

Monuron ; sodium chlorate

p

p

MCPA

Herbicidal oils ; 2,4-D

<5T»otted (H. Dunctatum) p

w

w

86 Atrazine ; simazine ; 2,4-D ; 2,4,5-T

Salmonberry {Ruhus spectabilis) Amitrole ; silvex ; 2,4,5-T

2,4-D ; 2,3,6-TBA
76 AGRICULTURE HANDBOOK 269. U.S. DBPT. OF AGRICULTURE

TABLE 5.—Weed species cmd herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Salsify :

common. {See Goatsbeard, common.)

meadow. {Bee Goatsbeard

{T.pratenais),)

western {Tragopogón major)

Saltbush. ( Bee Orache. )

Saltcedar {Tamarix gallica)

Saltgrass, seashore {Distichlis spicata)

Saltwort, common. {See Russianthistle.)

Sandburs (CeticTirws spp.)

Sandspurry {Sper guiaría segetalis)

Sandwort, thymeleaf {Arenaria

serpylUfolia).

Saskatoon {Amelanehier alnifolia)

Sassafras {Sassafras varifolium and

S, albidum).

Scotch-broom {Cytisus scoparius)

Seamyrtle {Baccharis halimifolia)

Sedge {Carex spp.)

Sesbania. (SeeCoffeebean.)

Shadbush or serviceberry {Amelanr

chier eanadensis).

Shepherds-purse {Gapsella hursapastoris),

Sicklepod. {See Coffeeweed {Cassia

tora).)

Sida, alkali or mallow {Sida hederacea)

Silverberry. {See Wolfwillow.)

Silverweed {Potentilla anserina)

Skeletonweed {Lygodesmia júncea)

Skunkbrush {Schmaltzia trilohata)

Skunkcabbage {Symplocarpus

foetidus),

Skunkweed. {See Crotón, Texas.)

Smartweed

green {Polygonum soahrum)

Japanese (P. cuspidatum)

ladysthumb (P. persicaria)

Pennsylvania (P. pennsylvanicum)

swamp (P. coccineum)

water (P. ampMMum)

water (P. hydropiper)

S—

W_

Ww_

P__ 34-36

55

A

A or B__

A or B__

A

WW_

WW_

W_

W_

P_-

41,44,

45,47

35,45

R__

S-_

S__

I__

s__

w_

WA_-

34

P

P

W

W

P

P

41

A or P_.

A

A

P

P

A

A

A

A

56

A__

A__

Aq_

Aq_ 35

2,4-D

Silvex

2,4,5-T

MCPA ; 2,4-D

Diuron ; erbon ; monuron ; sodium arsenite ;

sodium chlorate

Dalapon ; fortified oils ; TCA

Silvex ; 2,4-D ; 2,4,5-T

DNC

MCPA ; 2,4-D

2,4-D

Do.

AMS ; fenac ; fenuron ; fenuronTCA ; monuron ;

2,4-D ; 2,4,5-T ; 2,3,6-TBA

Amitrole

2,4-D ; 2,4,5-T

Do.

CBMM ; diuron ; fenuron ; monuron

Amitrole ; AMA ; atrazine ; dalapon ;

herbicidal oil + DNBP

BMM ; erbon ; monuron

MCPA; 2,4-D

Fenuron ; 2,4-D

Amitrole

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Fenac ; 2,3,6-TBA

Erbon

Sodium chlorate ; 2,4-D

2,4-D

Do.

Do.

2,4,5-T

2,4-D; 2,4,5-T

Silvex

Dicamba

DMPA ; endothall ; MCPA ; sUvex ; 2,4-D

AMS ; BMM ; erbon ; monuron ; silvex ; TCA

2,4-D ; 2,4,5-T

Silvex ; 2,4,5-T ; 2,3,6-TBA

MCPA

DCPA

MCPA ; 2,4-D ; 2,4,5-T ; 2,3,6-TBA

Silvex

BMM ; DCPA

Diuron ; monuron

PBA ; 2,3,6-TBA

Amitrole ; 2,4-D

2,4-D

Amitrole ; diuron ; monuron
HERBICIDE MANUAL 77

TABLE 5.—Weed species a/nd herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Smilax {Smilax spp.)

Smutgrass {Sporoholus poiretii)

Snakeroot, white {Eupatorium

rugosum).

Snakeweed :

broom {Chitierrezia sarothrae)

threadleaf. {See Broomweed,

threadleaf. )

Sneezeweed, bitter. {See Bitterweed.)

Snowberry, western. {See Buckbrush.)

Snowbmsh {Ceanothus velutinus)

Snow-on-the-mountain {Euphorbia

marginata).

Sorrel :

heartwing {Rumex hastafulus)

red or sheep {R. acetosella)

sour dock {R. acetosa)

Sourwood {Oxydendrum arhoreum) —

Sowthistle :

annual {Sonchus oleraceus)

W

W

W

AorPAorP_

P

P

55

P

P

perennial {8. arvensis)

spiny {S. asper)

Spanish-needles {Bidens hipinnata)

Spatterdock {Nuphar advena)

Speedwell :

{Veronica spp.)

purslane {V. peregrina) _

Spicebush {Lindera benzoin)

Spikegrass. {See Saltgrass, seashore.)

Spikerush :

{Eleocharis spp.)

creeping {E, párvula)

Spirea {Spiraea spp.)

Sprangletop :

Mexican {LeptocMoa univervia)

red {L. ßUformis)

Spruce :

{Picea spp.)

black (P. mariana)

white (P. glauca) _

W__

W—

W—

A

A__.

S__

I__

R__

S__

I__

P__

P__

P__

P__

P__

P__

w_ 45

A__

A_-

P_- 35

P__.

A—

A__

Aq_

Aq_

P_.

P__

P__

P_-

Ww_

p__

Aq_

Aq_

WA__

A__

WW_

Ww_

56,57

50

36,56

S

R

AMS

Penuron

Amitrole ; MCPA ; monuronTCA ; silvex

Amitrole

Silvex ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

Silvex

MCPA; 2,4-D; 2,4,5-T

Silvex

2,4,5-T

2,4-D

Amitrole ; AMS ; silvex

2,4,5-T

2,4-D

Do.

Dicamba ; 2,3,6-TBA

Silvex

Amitrole ; erbon ; MCPA ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

MCPA ; süvex

Monuron ; 2,4-D

MCPA; 2,4-D; 2,4,5-T

CBM ; CBMM

Dicamba ; fenac ; simazine ; sodium chlorate ;

2,3,6-TBA

Amitrole ; diuron ; MCPA ; monuron ;

monuron TCA ; silvex ; 2,4-D ; 2,4,5-T

CBMM

2,4-D ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

Silvex

2,4-D

Monuron ; sodium chlorate

2,4-D

MCPA ; silvex ; 2,4,5-T

MCPA ; silvex ; 2,4-D ; 2,4,5-T

AMS ; 2,4-D ; 2,4,5-T

Amitrole

Silvex ; 2,4-D ; 2,4,5-T

MCPA ; simazine ; 2,4-D

Silvex ; 2,4,5-T

Diuron ; simazine ; 2,4,5-T

Silvex; 2,4-D; 2,4,5-T

Do.

AMS ; 2,3,6-TBA

Dalapon ; TCA

Amitrole

2,4-D ; 2,4,5-T
78 AGRICULTURE HANDBOOK 269, U.S. DEPT. OP AGRICULTURE

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Spurge :

flowering {Euphorbia corollata)

leafy {E. esula)

upright or spotted {E. maculata) —

Spurry, corn {Spergula arvensis)

Squawberry {Rhus trilohata)

Squirreltail {Sitanion bystrix)

Star-of-Bethlehem {Ornithogalum

umhellatum).

Star-thistle :

meadow {Centaurea pratensis) —

yellow {C. solstitialis)

Stickseed, or sticktight, European

{Lappula echinata).

Stinkgrass {Eragrostis cilianensis) —

Stinking-Willie. {See Tansy-ragwort.)

Stinkweed. {See Pennycress, field.)

Stinkwort {Irmla graveolens)

Stonewort {Chara spp.)

Strawberry, wild {Fragaria s^^^.)

Sumac {Rhus spp.)

Chinese {Ailanthus spp.)

smooth {Rhus glabra)

staghorn {R. typhina)

Sumpweed, rough {Iva ciliata)

Sunflower :

common {Helianthus annuus)

prairie {È. petiolaris)

Swamp-loosestrife {Decodon verticillatus).

Sweetclover, yellow annual {Melilotus

indica).

Sweetfern {Comptonia peregrina)

Sweetgrass, floating {Olyceria fluitans)

Sweetgum {Liquidambar styradflua) —

Swinecress {Coronopus didymus)

Sycamore {Platanus occidentalis)

Tamarack {Larix laricina)

Tanoak:

{Lithocarpus densißora)

scrub {L. densiflora var. montanus).

Tansy {Tanacetum vulgäre)

Tansymustard {Descurainia pinnata).

Tansy-ragwort {Senecio jacobaea)

P__

P__

P__

P__

P__

A__

A—

A__

A__

A__

W_

P__

P__

P__

34,35

37,51

AorB_

A

A

A

I

I

R__

S__.

51,52

P__

AqAq_

P__

P__

WWT,41,

44, 45,

47

WW_

WWWA_.

A__

A__

Aq_ 56

WAq_

Aq_

WWWA—

WW41,45

41

W

W

R

R

P

P

A

P

P

35

2,4,5-T

2,4-D

AMS ; erbon ; fenac ; PBA ; 2,3,6-TBA

MonuronTCA ; silvex

Amitrole-T ; MCPA ; simazine ; 2,4-D ; 2,4,5-T

BMM ; CBMM ; DCPA ; silvex

2,4-D ; 2,4,5-T

Dicamba

MCPA ; silvex

2,4-D ; 2,4,5-T

Silvex ; 2,4,5-T

MCPA ; 2,4-D ; 2,4,5-T

2,3,6-TBA

2,4-D

MCPA ; 2,4-D

2,4-D

Herbicidal oils ; sodium arsenite

2,4-D

Calcium and lead arsenate ; chlordane ;

DCPA ; DMPA

2,4-D

Copper sulfate

Sodium arsenite

Silvex

MCPA ; 2,4-D ; 2,4,5-T

AMS ; fenuroh ; 2,4-D ; 2,4,5-T ; 2,3,6-TBA

Amitrole ; fenuronTCA

Silvex ; 2,4,5-T

AMS ; 2,4-D

MCPA

Brush killer

Amitrole ; brush killer

2,4-D

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

Silvex

MCPA ; 2,4-D

PBA ; 2,4-D ; 2,3,6-TBA

Dalapon; diuron; monuron

Copper sulfate ; silvex ; sodium chlorate •

2,4-D

AMS ; fenuron ; 2,4,5-T

Silvex

2,4-D

Do.

AMS ; fenuron ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

Silvex ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

Do.

MCPA

2,4-D

Sodium chlorate ; 2,4-D

Diuron ; MCPA ; monuron ; silvex ; 2,4,5-T
HERBICIDE MANUAL 79

TABLE 5.—Weed species and herbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicideHerbicide

Tanweed. {See Smartweed, swamp.)

Tarbush {Flourensia cernua) W

W

W

Tarweed, fiddleneck. {See Fiddleneck,

coast. )

Thimbleberry {Rubus parviflorus)

Thistle :

bristly {Cirsium horridulum)

bull. {See Bullthistle. )

Canada {C. arvense)

W_

WB and PP

I

34, 35,

37,50

wavyleaf (0. undulatum)

Thornapple. {See Hkwthorn {CrataeTickseed {Coreopsis tinctoria)

Tievine {Jacquemontia tamnifoUa) —

Toadflax, yeUow {Linaria vulgaris) __

Torpedograss {Panicum repens)

Toyon {Heteromeles arhutifolia)

Tree-of-heaven {Ailanthus altissima).

A

A

P

P

Trumpetcreeper or trumpetvine

( Campsis radicans).

Tule. (See Bulrush.)

Tuliptree {Liriodendron tulipifera) __.

Tumblemustard {Sisymhrium altissimum ).

Tumbleweed. {See Pigweed, tumble.)

Tupelo. ( See Gum, black. )

Turks-rug {Chorizanthe staticoides)^-.

Umbrella-sedge {Cyperus difformis) __.

Vaseygrass {Paspalum urvillei) _

Velvetleaf {Abutilón theophrasti)

P

P

W

W

w

w

w

w

w

w

55

W_

WA_-

Venus-lookingglass {Specularia

perfoliata).

Vervain {Verbena spp.)

Vetch :

narrowleaf {Vicia angustifolia) __.

wild (Ficia spp.)

Viburnum, maple-leaf {Viburnum

spp.).

Violet {Viola spp.)

Virginia-creeper {Parthenocissus

quinquefolia).

Walnut, black {Juglans nigra) _.

Waterchestnut {Trapa natans) _.

Watercress {nasturtium officinale) __

A

A

A

AorPA or P_

A

A

A

35,37

A

A

A

W

P_.

P__

WWAq_

Aq_

Aq_

41

56

56

Fenuron ; fenuronTCA ; monuron ; 2,4-D

Silvex ; 2,4,5-T

2,3,6-TBA

2,4,5-T

2,4-D

Do.

Amitrole ; AMS ; atrazine ; BDM ; CBM ;

dicamba ; fenac ; PBA ; sodium chlorate ;

2,3,6-TBA

BMM ; diuron ; MCPA ; monuron ; monuronTCA ;

sUvex ; 2,4-D ; 2,4,5-T

Amitrole-T ; erbon ; simazine ; sodium arsenite

MCPA ; 2,4-D

2,4-D ; 2,4,5-T

Silvex

Diuron ; monuron

Amitrole ; BMM ; MCPA ; monuronTCA ;

silvex; 2,4-D; 2,4,5-T

Amitrole

MonuronTCA

2,4-D

MCPA ; silvex ; 2,4,5-T

Silvex ; 2,4,5-T

AMS ; 2,4-D

MCPA

AMS ; silvex

2,4-D ; 2,4,5-T

Amitrole

AMS ; 2,4,5-T

Amitrole ; fenuron

MCPA; 2,4-D; 2,4,5-T

Sodium arsenite

MCPA ; 2,4-D

Silvex ; 2,4,5-T

BMM ; CBMM ; diuron ; monuronTCA

Simazine ; TCA

MCPA ; 2,4-D ; 2,4,5-T

DCPA

2,4-D

Do.

2,4-D ; 2,4,5-T

MCPA

MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D ; 2,4,5-T

Silvex

MCPA ; 2,4-D

2,4-D ; 2,4,5-T

Do.

MCPA ; 2,4-D

Monuron ; silvex ; 2,3,6-TBA

Monuron ; 2,4-D
80 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

TABLE 5.—Weed speoies cmd herhicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Watercrowfoot {Ranunculus aquatilis).

Waterfern {Azolla spp.)

Waterhemlock :

{Cicuta douglasii)

spotted (0. maculata)

Water-horehoTind {Lycopus americanus ).

Water-hyacinth {Eichomia crassipes).

Waterlettnce {Pistia stratiotes)

Waterlily {Nymphaea spp.)

Watermilfoil {Myriophyllum heterophyllum).

Waterplantain, common {Alisma

triviale),

Waterprimrose {Jussiaea spp.)

Waterpurslane {Ludwigia palustris)

Watershield {Brasenia scJireberi) __

Water-stargrass {Heterantha duhia) _.

Water-starwort {Gallitriche verna) __.

Waterweed, Canada {Elodea canadensis),

Wedgeleaf. {See Ceanothus, wedgeleaf.)

Whitebnish {Aloysia lycioides)

White-cedar {Thuja occidentalis)

Whiteclover {Trifolium repens)

White-locoweed {Oxytropis lambertii).

Whitethorn :

{Acacia constricta)

mountain {Ceanothus cordulatus).

Whitetop {Cardaria draha)

Wildbuckwheat {Polygonum convolvulus).

Wildcelery {Vallisneria si^^.)

Wildcucumber. {See Burcucumber.)

Wildflax. ( See Tickseed. )

Wild-indigo {Baptisia tinctoria)

WiUow {Salix spp.)

WiUowweed or willow-herb {Epiloöiwmspp.).

Windmillgrass, tumble {Chloris verticillata),

Wintercress. {See Yellow-rocket.)

Witchgrass. {See Panicum.)

Witch-hazel {Betula lutea var.

macrolepsis).

AQ_

AqAqAqAq_

Aq_

AqAq_

Aq_

Aq_

AqAq_

Aq_

Aq_

Aa_

Aq_

AqAq_

Aq_

AqW_

W_

WP__

P__

w_

w_

w_

w_

w_

p__

p__

A

A

A__

AqP__

P__

WWW_

WP

w_

53

"53'

S_

S

s

7,53

53

53, 56,

57

53,54

56,57

'53^56'

53'

53-55

43

'51'

35,36

S

36, 43,

44,47

Acrolein ; aromatic solvents ; diuron ; monuron ;

sodium arsenite

Silvex

Invert emulsion of 2,4-D and 2,4,5-T

2,4-D

Silvex; 2,4-D; 2,4,5-T

2,4-D

Amitrole-T ; silvex ; 2,4-D ; 2,4,5-T

Herbicidal oils ; invert emulsion of 2,4-D

and 2,4,5-T ; simazine

Erbon ; silvex ; 2,4-D

Dalapon ; sodium arsenite

Acrolein ; aromatic solvents ; dichlone ;

endothall ; silvex ; simazine ; 2,4-D ; 2,4,5-T

MCPA; silvex; sodium arsenite; 2,4-D; 2,4,5-T

Copper sulfate

Acrolein ; diuron ; fenuron ; monuron ; silvex ;

2,4-D ; 2,4,5-T

Monuron ; sodium arsenite

Silvex

2,4-D ; 2,4,5-T

Copper sulfate ; monuron ; sodium arsenite

Acrolein ; aromatic solvents ; silvex ; sodium

arsenite ; 2,3,6-TBA

SUvex

Copper sulfate

Acrolein ; aromatic solvents ; diquat ; diuron ;;

sodium arsenite

Copper sulfate ; MCPA ; 2,4-D

MCPA

Dalapon ; TCA

Amitrole ; simazine

Endothall ; silvex ; 2,4-D ; 2,4,5-T

Silvex ; 2,4-D ; 2,4,5-T

Fenuron ; fenuronTCA ; monuron

Silvex ; 2,4-D

2,3,6-TBA

2,4,5-T

Amitrole; 2,4-D

Amitrole

CBM ; diuron ; MCPA ; monuron ; monuronTCA ;

silvex ; sodium chlorate ; 2,4-D ; 2,4,5-T

Dicamba ; fenac ; monuron ; sodium chlorate ;

2,4,5-T ; 2,3,6-TBA

MCPA; silvex; 2,4-D

Amitrole

Silvex ; sodium arsenite

2,4,5-T

2,4-D

AMS ; MCPA ; monuron ; silvex ; 2,4-D ; 2,4,5-T :

2,4rD + TCA ; 2,4,5-T -f TCA

Diuron ; DNBP ; simazine ; 2,3,6-TBA

Amitrole ; fenuron

Silvex ; 2,4-D ; 2,4,5-T

2,4-D

AMS ; 2,4,5-T
HERBICIDE MANUAL 81

TABIXE 5.—Weed species cmd Tierbicides for control—Continued

Weed species Growth

habit Page

Response

to herbicide

Herbicide

Witchweed (Striga asiática) _

Wolfberry. (See Buckbrush, snowberry.)

Wolfwillow {Elaeagn/us commutata) __

Woodsorrel, yellow {Oxalia stricta)

A .

W

A or P

AorP _

--

S

S

R"""""

s

s_

I

s

I

I

R

I

R

S -. -

s

I

s

I -

s

RI

R

Fenac ; MCPA ; silvex ; 2,4-D ; 2,4,5-T

2,4-D

Silvex

MCPA ; 2,4-D

Woolgrass. ( See Bulrush. )

Wormseed-mustard {Erysimum

vheiranthoides),

Wormwood :

absinthe. {See Absinthe.)

annual (Artemesia annua) -

biennial {A. Mennis)

A

A_

A

B

P

P

P _

MCPA ; silvex ; 2,4-D ; 2,4,5-T

50

2,4-D ; 2,4,5-T

MCPA

MCPA; 2,4-D

Yankeeweed {Eupatorium compositifolium).

Yarrow :

common {Achillea millefolium)

2,4-D ; 2,4,5-T

MCPA; süvex; 2,4,5-T

2,4-D

western {A. lanulosa) _ - P

W _ -

2,4-D ; 2,4,5-T

Yaupon {Ilex vomitoria) 2,4-D ; 2,4,5-T ; 2,3,6-TBA

Yellow-rattle {Rhinanthus spp. )

Yellow-rocket {Barbarea vulgaria) —

Yerba-santa {Eriodictyon califomicum)

Yucca:

(Yucca sm^liana) -

A , B or P

BorP

W ^ -

W

w

-- MCPA; 2,4-D

MCPA; 2,4-D; 2,4,5-T

Silvex

MCPA; 2,4-D; 2,4,5-T

SUvex

Do.

W Amitrole ; diuron ; monuron ; monuronTCA

soapweed (Y. glauca) W

W

Silvex

2,4-D; 2,4,5-T
HERBICIDE MANUAL 83

APPENDIX

LIST OF EQUIVALENTS

Linear measure

1 inch=2.54 centimeters

1 yard=3 feet

1 rod=5.5 yards=16.5 feet=5.03 meters

1 mile=320 rods=l,760 yards=5,280 feet=

1.6093 kilometers

1 kilometer=0.621370 mile

1 meter=39.37 inches = 1.0936 yards

Square measure

1 square foot=144 square inches

1 square yard=9 square feet

1 square rod=272.25 square feet =

30.25 square yards

1 acre=43,560 square feet=4,840 square

yards=160 square rods=0.404687 hectare

=an area 208.7 feet square

=an area I6I/2 feet (1 rod) X V^ niile

1 hectare=2.47 acres

1 square mile=640 acres=259 hectares

Capacity measure (cubic)

1 cubic inch=16.387 cubic centimeters

1 cubic foot=1,728 cubic inches=29.922 US

liquid quarts=25.714 US dry quarts=

0.80357 US bushel=28.316 liters

1 cubic yard=27 cubic feet

Capacity measure (liquid)

1 level tablespoon=3 level teaspoons

1 fluid ounce=2 tablespoons=29.57 cubic

centimeters

1 cup=8 fluid ounces=16 tablespoons

1 pint=2 cups=16 fluid ounces=473.2 cubic

centimeters

1 quart=2 pints=32 fluid ounces=0.9463 liter

1 gallon=4 quarts=128 fluid ounces=

231 cubic inches=0.1337 cubic feet=

3.785 liters=16 cups=256 tablespoons

1 milliliter=almost exactly 1 cubic centimeter

1 liter=1,000 milliliters=1,000 cubic centimeters=1.057 liquid quarts

Capacity measure (dry)

1 quart=2 pints=67.20 cubic inches=

1.1012 liters

1 bushel = 32 quarts=4 pecks = 1.244 cubic

feet=2150.42 cubic inches =35.238 liters

1 liter=0.9081 dry quart=0.028378 bushel

Weight

1 grain=64.7989 milligrams

1 ounce (avoirdupois) =437.5 grains=

28.3495 grams

1 pound (avoirdupois) =16 ounces=7,000

grains=453.59 grams

1 ton (short) =2,000 pounds =907.185 kilograms

1 ton (long) =2,240 pounds=1.120 short tons

= 1,016.047 kilograms

1 microgram= 1 gamma =0.001 milligram

1 gram = 1,000 milligrams=15.432 grains =

0.0353 ounce

1 kilogram= 1,000 grams=35.27 ounces =

2.205 pounds

1 gallon water=8.355 pounds

1 cubic foot water =62.43 pounds

1 kilogram water=2.2046 pounds

1 gram water=15.432 grains=0.0353 ounces

Eate of speed

1 mile per hour=1.6093 kilometers per hour

=44.70 centimeters per second=88 feet per

minute

TABLE 6.—Relation of Centigrade and, Fahrenheit

scales ^

^'C. op "C. °F. «C. »p

-40 -40 0 32 40 104

-35 -31 5 41 45 113

-30 -22 10 50 50 122

-25 -13 15 59 55 131

-20 - 4 20 68 60 140

-15 5 25 77 80 176

-10 14 30 86 100 212

- 5 23 35 95

11° C. =1.80° F. ; I'' F.=0.56* C. To convert C. to F. : Multiply 0. by % and add 32. To convert F. to O. : Subtract 32 from F. and multiply by %.
84 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

GLOSSARY

The definitions and explanations in this glossary apply to words as they are used in this handbook. Some words have more comprehensive

meanings.

Acid equivalent—The theoretical yield of parent

acid from an active ingredient. It is used

instead of or in addition to the active ingredient for certain herbicides.

Active ingredient—The chemical compound in a

product that is responsible for the herbicidal

effects.

Adsorbed—^Held so tightly that the herbicide is

rendered inactive or only slowly effective.

The principal adsorbing agents of the soil

are its inorganic (clay) and organic (humus)

colloids.

Aliphatic materials—Chemically, those that have

an open-chain molecular structure. As herbicides, they are less toxic to plants than aromatic compounds.

Anionic surfactant—One that has a negative

charge and performs best in cold water and

soft water. Most wetting agents and detergents and some emulsifiers are anionic.

Annual—^A plant that completes its life cycle

from seed in 1 year.

API Gravity—Gravity of oils determined by the

American Petroleum Institute and expressed

in degrees API.

Aquatic weeds—^Undesirable plants that grow in

water.

Aromatic oils and solvents—Chemically, those

that have a ring molecular structure. As

herbicides, thej are generally more toxic to

plants than aliphatic materials.

Ballast—^A strip 12 to 16 feet wide made up of , coarse material or gravel on railroad roadbeds.

Basal-bark applications—^Herbicide treatments

applied to the stems of woody plants at or

just above the ground.

Berm—^A narrow band along a bank; along the

pavement on a highway ; along the ballast on

a railroad.

Biennial—^A plant that completes its life cycle

in 2 years. The first year it produces leaves

and stores food. The second year it produces

fruits and seeds.

Botanical plant name—A scientific name made

up of the genus and species. Sometimes the

variety or subspecies is included. It is more

reliable and more universal than common

names.

Broadcast application—Uniform distribution of

a herbicide over an entire area.

Broad-leaved plants—Botanically, those classified

as dicotyledons. Morphologically, those that

have broad, usually compound leaves.

Carrier—The liquid or solid material added to a

chemical compound to facilitate its application in the field.

Cation exchange—The exchange of positive ions

(H, Ca, Mg, Na, NH4) from clay particles

for other cations. Soils are able to filter out

salts in much the same way a water softener

removes them. Some soils have a larger capacity than others for doing this. Such soils

can adsorb or filter out and hold large

amounts of a herbicide so that it is not immediately effective. The cation exchange capacity of a soil can be learned from the State

agricultural experiment station.

c.f.s.—Cubic feet of water flow per second.

Chemical name—One that indicates the chemical

composition of the compound and also the

structure of the molecule in organic compounds.

Common plant name—^An English name in common use. A plant may be ]mown by several

different common names, and one common

name may be used for different plants in different parts of the country. Many common

names are local.

Compatible pesticides—Compounds or formulations that can be mixed and applied together

without undesirably altering their separate

effects.

Concentration—The amount of active iagredient

or acid equivalent in a given volume of liquid

or in a given weight of dry material.

Contact herbicide—One that kills primarily by

contact with plant tissue rather than as a result of translocation.

Cut-surface applications—Treatments made to

frills or girdles that have been made with

an ax through the bark and well into the

wood of woody plants.

Deciduous trees—Those that lose their leaves during winter.

Detergent—A chemical (not soap) having the

ability to remove soil or grime. Household

detergents can be used as surfactants in herbicide sprays.

Diluent—Any liquid or solid material that dilutes

an active ingredient in the preparation of a

formulation.
HERBIOIDE MANUAL 85

Dormant spray—^A herbicide applied during the

period after leaf-fall or death of leaves and

before bud-break of deciduous trees.

Emulsifiable concentrates—^Usually liquids in

which the chemical is dissolved in one or

more water-insoluble solvents such as oil or

benzene to which an emulsifier is added.

Emulsifier—A surface active material that facilitates the suspension of one liquid in another.

Emulsion—^The suspension of one liquid as minute

globules in another liquid; for example, oil

dispersed in water.

Escape—^A plant in a treated area that has missed

treatment. For example, an annual or shallow-rooted perennial that re-infests an area

after the chemical has been leached below the

surface ; a perennial, part of whose root system is below the treated layers of soil; or a

plant that was missed at the time of application.

Extruded—^A process in which a powdered carrier

mixed with the herbicide is moistened until

it becomes plastic and then is forced or expelled as rods. These rods are dried, ground,

and screened to the required screen mesh for

a granular formulation. This process increases internal pore volume and surface area.

The product is frequently referred to as AA

in contrast to A materials, which have not

been subjected to an extrusion process.

Formulation—^A term used synonymously with

product. It contains the herbicide in a form

that can be (1) dissolved or suspended in a

carrier and distributed in solution or suspension by sprayers, (2) distributed dry by dusters or spreaders, or (3) easily vaporized for

fumigation.

Fortified—^Herbicidal properties increased by addition of PCP, DNC, DNBP, or OCH.

Sp.m.—Gallons per minute,

ranular products—^Formulations in which the

chemical is impregnated on or in vermiculite,

attaclayj or other suitable carrier and then

formed mto granules or pellets.

Grass—Botanically, any plant of the Gramineae

family. Grasses are characterized by narrow

leaves with parallel veins; by leaves composed of blade, sheath, and ligule; by jointed

stems and fibrous roots; and by inconspicuous flowers usually arranged in spikelets.

Growth regulator—^An organic substance effective

in minute amounts for controlling or modifying plant processes.

Hard water—^Water that contains certain minerals, usually calcium and magnesium sulfates,

chlorides, or carbonates, in solution in

amounts that cause a curd or precipitate instead of a lather when soap is added. Generally defined as containing 322 p.p.m. in

terms of calcium carbonate. Very hard water

may cause precipitates in some herbicidal

sprays.

Herbaceous plant—^A vascular plant that does not

develop woody tissue. It dies down each

year.

Herbicide—^A phytotoxic chemical used for killing or inhibiting the growth of plants.

h.p.—^Horsepower.

Intermediate species—One whose response to a

herbicide is in between the response of a susceptible and a resistant species. It is severely injured or partially controlled by

higher than moderate rates.

Invert emulsion—One in which oil is the continuous phase and water is dispersed in it.

Ionic surfactant—One that ionizes or dissociates

in water.

Isomers—^Two or more substances having the

same chemical composition but different

properties.

Leaching—Movement of a substance in solution

downward through the soil.

L.D.g^—Lethal dose m milligrams per kilogram

of body weight for 50 percent of the ammals

tested.

Low-volatile ester—Chemically, an ester with a

heavy molecular weight such as the butoxyethanol, iso-octyl, or propylene glycol butyl

ether esters. Low-volatile esters do not include the methyl, ethyl, propyl, isopropvl,

butyl, amyl, and pentyl esters. Biologically,

an ester that is less liable than the high-volatile esters to injure plants by vapor activity.

Nonionic surfactant—Chemically inert.

Nonselective herbicide—^A chemical that is toxic

to plants generally without regard to species.

Organic matter—^Plant or animal remains in the

soil.

Perennial—^A plant that lives more than 2 years.

pH—The chemist's measure of acidity and alkalinity. It is a scale in which the figure 7

indicates neutral, figures below 7 indicate

acidity, and figures above 7 indicate an alkaline reaction.

Photosynthesis—^The process by which carbohydrates are manufactured by the chlorophyUbearing cell granules (chloroplasts) from

carbon dioxide and water by exposure to the

energy of sunlight.

Phytotoxic—^Poisonous to plants.

Plow sole—Compact layer just below plow depth.

Postemergence—^After emergence of specified

weed.

p.p.m.—^Parts per million.

Preemergence—^Prior to emergence of specified

weed.

Preplanting—^Any time before the crop is planted.

Product—^The herbicide as it is sold commercially.

It contains not only the active ingredients but

also various solvents, cosolvents, surfactants,
86 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

carriers, and other adjuvants that are designated as inert ingredients.

Proprietary mixture—One that is commercially

available.

p.s.i.—^Pounds per square inch.

Rate—The amount of active ingredient or acid

equivalent of a herbicide applied to a unit

area.

Eesistant species—One that is difficult to kill; the

use of the herbicide is not recommended.

r.p.m.—Revolutions per minute.

Selective herbicide—^A chemical that is more toxic

to some plant species than to others.

Slurry—^A watery mixture or suspension of an insoluble herbicide.

Soil application—^Application of herbicide made

primarily to the soil surface rather than to

vegetation.

Soil colloid—^Extremely small particles of clay or

organic matter that expose a very large surface area on which some herbicides are adsorbed.

Soil sterilant—^A herbicide that prevents the

growth of green plants when present in the

soil. Soil sterilization effects may be temporary or relatively permanent. It does not

necessarily kill all life in the soil such as

fungi, bacteria, and other micro-organisms.

Soil structure—^Arrangement of soil particles into

separate grains or granules.

Soil texture—Proportion of sand, silt, and clay

in the soil; size of soil particles.

Solvent—The component of a solution that dissolves the other components.

Species—^A subdivision of a genus. A group of

closely related individuals descendant from

the same stock.

Spot treatment—^Application of a herbicide to individual plants or small clumps of plants.

Spray drift—The movement of airborne spray

particles from the intended area of application.

Spreader-sticker—A surfactant closely related to

wetting agents that facilitates spreading and

increases sticking of a herbicide on vegetation.

Stem-foliage application—An application of a

herbicide to both stems and leaves of a plant.

Surfactant—A material that improves the emulsifying, dispersing, spreading, wetting, and

other surface-modifying properties of herbicide formulations.

Susceptible species—One that can be killed with

moderate rates of a herbicide.

Suspension—A system consisting of very finely

divided solid particles dispersed in a liquid.

Translocated herbicide—One that is moved within

the plant from the point of entryVapor drift—^The movement of herbicidal vapors

from the area of application.

Viscosity of oil—Expressed in time (seconds) required for 60 C.C. of heated oil to flow through

a Saybolt Universal Viscosimeter.

Volatile—^A compound is volatile when it evaporates or vaporizes (changes from a liquid to

a gas) at ordinary temperatures on exposure

to the air.

Water-dispersible powder—^A finely ground powder plus a wetting agent plus a dispersing

agent to keep the material in suspension.

Weed—A plant growing where it is not desired.

Weed eradication—^The complete elimination of

all live plants, plant parts, and seeds of a weed

infestation from an area.

Wettable powder—^A finely ground powder plus a

wetting agent to keep the particles from floating when added to water.

Wetting agent—^A compound that when added to

a spray solution causes it to contact plant surfaces more thoroughly.

WSA—^Weed Society of America.
HERBICIDE MANUAL 87

HERBICIDE INDEX

Herbicides are listed by approved common name, chemical name and WSA designation. Group names, based on

use or mode of action, and chemical family names are also

listed.

Page

6,56

Herbicide

Acrolein

Acrylaldehyde. (See Acrolein.)

AMA. (fi^ee Amine methylarsonate.)

Amine methylarsonate g 52

3-Amino-l,2,4-triazole. Jsee Anaitrole.)

3-Amino-l,2,4-triazole-ammonium thiocyanate

(See Amitrole-T.)

Amitrole 6, 37, 40, 43, 46-48, 55. 57

Amitrole-dalapon 3g

Amitrole-monuron ~ ~ III_~ I_ 38

Amitrole-simazine _Vl4"38 47

Amitrole-T I ~ "7' 37* fiS

Amitrole-TCA I~IIIIIII.J__ 38

Ammonium methylarsonate. i8ee Amine

methylarsonate.)

Ammonium sulfamate 7, 43, 44-46, 48

AMS. (See Ammonium sulfamate.)

Aromatic oils 13,39^ 55

Aromatic solvents 12,52,55,56

Arsenicals 7] 33

Atrazine ~ 19' 35

BDM. (See Borate-2,4-D.)

Benzole acid compounds 8, 34

BMM. (/8fee Borate-monuron.)

Borate-2,4-D 14^ 37

Borate-monuron 14, 36* 54

Brush killer (2,4-D + 2,4,5-T) 47,48,53

Calcium arsenate 8, 51

Carbon disulfide Z I_ 11, 49

CBM. (See Chlorate-borate.)

CBMM. (See Chlorate-borate-monuron.)

Chemical combinations 9

Chlorate-borate 14, 37,40, 46

Chlorate-borate-monuron 14, 37, 54

Chlorate-chloride 14

Chlordane 12. 52

Chlorinated hydrocarbons 12

2-Chloro-4,6-bis (ethylamino ) -s-triazine.

(See Simazine.)

2-Chloro-4-ethylamino-6-isopropylamino-s-triazine.

(See Atrazine.)

3- (p-Chlorophenyl) -1,1-dimethylurea.

(See Monuron.)

3- (p-Chlorophenyl) -1,1-dimethylurea

trichloroacetate. (See Monuron TCA.)

Chloropicrin 11, 49

Contact herbicides 2,38

Copper sulfate 9,53,54,56

2,4-D 15, 40, 41, 43-^6, 49, 50, 51, 53, 55-57

Dacthal. (See 2,3,5,6-Tetrachloroterephthalate.)

Dalapon 10, 37, 40, 43, 47, 50, 52, 55, 57

Dalapon-silvex 14, 38, 40, 57

DCPA. (See 2,3,5,6-Tetrachloroterephthalic acid.)

Dicamba 8, 51

Dichlone 10, 54

2,3-Dichloro-1.4-napthoquinone. ( See Dichlone. )

3- (3,4-Dichlorophenyl) -1,1-dimethylurea.

(fi'eeDiuron.)

2,4-Dichlorophenoxyacetic acid. (See 2,4-D.)

0- (2,4-Dichlorophenyl) -0-methyl

isopropylphosphoramidothioate 10, 51

2,2-Dichloropropionic acid. (iSfee Dalapon.)

Diesel oil 12 13 39 53

6-7-Dihydrodipyrido a,2-A:2M"-C) pyrazidiinium

salt. (ßfeeDiquat.)

l,2-Dihydropyridazine-3,6-dione. (See Maleic

hydrazide. )

3,5-Dimethyltetrahydro-l,3,5,2H-thiadiazine2-thione 12 49

Dinitro compounds II_II 10,' 39

4,6-Dinitro-o-sec-amylphenol. (^¿ee DNAP. )

4,6-Dinitro-o-sec-butylphenol. (See DNBP.)

3,5-Dinitro-o-cresol. (;Sfee DNC.)

Diquat 11, 54

Disodium methane arsonate hexahydrate.

(See Disodium monomethylarsonate.)

Disodium monomethylarsonate 8, 52

Diuron is, 35, 40, 47, 54, 55

DMA. (See Disodium monomethylarsonate.)

DMPA. (See 0- (2,4-dichlorophenyl ) -0-methyl

isopropylphosphoramidothioate.)

DMTT. ( See 3,5-dimethyltetrahydro-l,3,5,2Hthiadiazine-2-thione. )

DNAP 11, 39

DNBP 10, 39, 47, 51

DNC 11, 39

Emulsifiable oils 13

Emulsions 20, 24, 39

Endothall J n, 54

3,6-Bndoxohexahydrophthalicacid.

(/See Endothall.)

Erbon 9, 34, 40, 54, 57

Fenac n, 34

Fenuron ." _" 18, 45, 47^ 54

FenuronTCA 9, 45, 54, 57

Foliage-applied nonselective herbicides 37

Fortified oils 13,55

Fumigants n, 21, 48

Herbicidal oils 12, 38

Herbicides for aquatic weeds 52

Herbicides for control of all vegetation 33

Herbicides for control of poisonous plants 47

Herbicides for specific areas 39

Herbicides for turf weeds 48

Herbicides for weeds in woody plantings 47

Herbicides for woody plants 40

Hydrocarbons 12

Invert emulsions 21, 24, 53

Kerosene 12,13

Lead arsenate 8, 51

Light oils 13

Maleic hydrazide 13

MCPA 16, 50, 51

Medium to heavy oils 13

2-Methoxy-3,6-dichlorobenzoic acid. (See Dicamba.)

Methyl bromide 12, 49, 51

2-Methyl-4-chlorophenoxyacetic acid. (See MCPA.)

MH. (See Maleic hydrazide.)

Mineral spirits 12,13

Mixtures 14,38

Monobromomethane. (See Methyl bromide.)

Monuron 18, 35, 40, 45, 54
88 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

MonuronTCA 9,35,40,54

Nonvolatile temporary soil sterilants 49

OCH. (iSfee Octachlorocyclohexenone.)

Octachlorocyclohexenone 15,53

l,2,4,5,6,7,8,8-Octachloro-4,7-methane3a,4,7,7a-tetrahy(iroliidane ; 1,2,4,5,6,7,

8,8-octaclüor-2,3,3a,4,7,7a-hexahydro4,7-methanoindene. (See Chlordane.)

PBA. (See Polychlorobenzoic acid.)

PCP. {See PentachlorophenoL)

Pentachlorophenol 15,39,40,56

Petroleum napthas. (See Aromatic solvents.)

Phenoxy compounds 15

3-Plienyl-l,l-dimethylurea. (See Fenuron.)

3-Plienyl-l,l-dimethylurea trichloroacetate.

(See FenuronTCA.)

Phenylmercurlc acetate 19,52

Phenylurea compounds 18

PMA. (See Phenylmercurlc acetate.)

Polychlorobenzoic acid 8

Selective herbicides 40,47,50,51

Silvex 17, 40, 43, 46, 50, 51, 53, 54, 56

Simazine 19,35,40,47,49,53-55

SMDC. ( See Sodium-2^-methyldithiocarbamate.)

7, 34,44-46, 52-55

19,86

12,48

Sodium arsenite

Sodium chlorate

Sodium-Ä'^-methyldithiocarbamate

Soil sterilants 14,33,36,38,40

Solvent napthas. (See Aromatic solvents.)

Special oils IS

Stoddard solvent 18

Stove oil IS

Suspensions 24

2,4,5-T 17, 41,43-48, 50, 51,53,56

TEA. (See 2,3,6-TBA.)

2,3,6-TBA. (See 2,3,6-Trlchlorobenzoic acid.)

TCA. (See Trichloroacetic acid.)

2,3,5,6-Tetrachloroterephthalic acid 9, 61

Tractor distillate 12

Triazines 19

Trichloroacetic acid 19, 36, 40, 43, 44, 47, 50, 55

2,3,6-Trichlorobenzoic acid 8,47

Trichloronitromethana (See Chloropicrin.)

2,4,5-Trichlorophenoxyacetic acid. (See 2,4,5-T.)

2-(2,4,5-Trichlorophenoxy)ethyl-2,2-

dichloropropionate. (See Erbon.)

2-(2,4,5-Trichlorophenoxy)propionic acid. (See Silvex.),

2,3,6-Trichlorophenylacetic acid. (See Fenac)
HERBICIDE MANUAL 89

GENERAL INDEX

Page

Acid equivalent 21

Active ingredient 21

Adsorption of herbicides 8

Annual plants 2

Appendix 83

Application equipment (see also Applicators, Sprayers,

and Spreaders) 24

calibration of 30

cleaning of 31

operation of 29

parts of

ground sprayers 26

aerial sprayers 28

storage of 32

Application of herbicides 32

aquatic weeds, for. (iSfee Aquatic weeds.)

complete control, for. (See Complete, or nonseleotive, vegetation control.)

granular products 28

rates. {See Rates and dates of application.)

regional

regions of similar soil and climatic conditions

(fig. 1.) 42

soil application recommendations by regions 45

weed control on and along railways by regions 40

woody weed control by regions 41,44

repeated vs. single applications 33

selective control, for. {See Selective control.)

specific areas, to. {See Specific areas.)

turf weeds, for. {See Turf.)

weeds in woody plantings, for 47

woody plants, for. {See Woody plants.)

Applicators 28

Aquatic weeds {see also Weed species and herbicides

for control, table 5) 52

emersed . 56

broad-leaved species 56

cattails and bulrushes 57

grass and grasslike species 57

ñoating 53

marginal 56

submersed 53

irrigation and drainage systems, in 54

ponds and lalies, in 53

reservoirs and large canals, in 56

Biennial plants 2

Brush control. {See Woody plants.)

Centigrade and Fahrenheit, relation of (table 6) 83

Classification of herbicides 2

Complete, or nonselective, vegetation control 33

factors affecting 2,32,33

failures 33

foliage-applied nonselective herbicides 37

contact 38

mixed 38

single-chemical 37

relatively permanent soil sterilants 33

mixed 36

single-chemical 33

specific areas, on. {See Specific areas.)

Contact herbicides

dinitros

emulsions

herbicidal oils .

2,38

10,39

20, 24, 39

12,38

Current herbicides 6

Disappearance of herbicides in soil 3

Drift 5, 30, 41, 46

Dusters and spreaders.

Dusts

{See Spreaders.)

21

Equipment. {See Application equipment.)

Emulsifiable concentrates 20

Equivalents 21

acid 21

active ingredients 21

list of 83

Factors affecting persistence of chemicals in soil.

Failure to obtain control, reasons for

Formulations

_ 83

. 20

dusts 21

emulsifiable concentrates 20

fumigants 11,21,48

granules 21

invert emulsions 21,24

oil-soluble concentrates 21

pastes 21

pellets 21

powders 21

surfactants 21

pentachlorophenol 15,39,40, 56

water-soluble concentrates 20

Fumigants 11, 21, 48

Glossary 84

Growth habits of weeds 2

Granules 21

Hazards {see also Herbicide index) 3

desirable plants, to 5

damage, causes of 5

drift, from 5, 30, 41, 46

foliage application, from 5,41, 55

leaching, from 5

spraying roadsides and under utility lines, from 46

washing, from 6

methods to reduce hazards to 20, 28,30,41,46

equipment, to 5

fish, to 6

game, to 6

handler, to 3

livestock, to 5

operator, to 3

Herbicides {see also Herbicide index) 2

adsorption 3

application. (See Application of herbicides.)

classification 2

contact 2

nonselective 2

selective 2

sterilant 3

mixtures 86

relatively permanent . 33

single-chemical 33

translocated 2

disappearance in soil 3

formulations. {See Formulations.)

labels 6

mixtures 14,36,38

purchase 21

storage 24

toxicity {see also Herbicide index) 3

relative acute toxicities (table 1) 4

Herbicide Index , 87
90 AGRICULTURE HANDBOOK 269, U.S. DEPT. OF AGRICULTURE

Invert emulsions 21,24

LD50 values

Mixing of spray materials 20, 22

amounts of liquid concentrate or of v^ettable powder

to use (table 2) 23

calculations for 22

emulsions 23

oil sprays 24

procedure for 23

suspensions 24

water sprays 23

Nonselective control. {See Complete, or nonselective,

vegetation control.)

Oil-soluble concentrates 21

Pastes 21

Pellets 21

Perennial plants 2

Persistence of chemicals in soil, factors affecting 3,33

Poisonous plants 47

Powders 21

Purchase of herbicides 21

Rates and dates of application 32

amounts of liquid concentrate or of wettable powder

to use (table 2) 23

aquatic weeds, for 52

complete vegetation control, for 33

poisonous plants, for 47

situations where light and heavy rates are called for

(table 4) 32

turf weeds, for 48

volume of spray - 32

weed control on railroads by regions, for 40

weeds in specific areas, for. {See Specific areas.)

weeds in woody plantings, for 47

woody plant control by regions, for 41

basal-bark application 44

foliage application 41

woody plants, for 40

Regions of similar soil and climatic conditions (fig. 1)_ 42

Reinfestation of land 40

Reproduction of weeds 2

Requirements for different types of sprays 28

Residual toxicity of herbicides {see also Herbicide

index) 33

Resistant weed species listed for each herbicide {see

also Weed species and herbicides for control (table 5) 32

Selective control 2

broad-leaved weeds in turf 50

definition of 2

irrigation and drainage systems, in 54

weeds in woody plantings 47

weedy grasses in turf 51

woody plants 40

Soil-sterilant chemicals. {See Herbicides.)

Specific areas {see also Application equipment)

bridges and buildings 7,14, 33

ditchbanks '^» 55

electrical installations 19

fence rows, firebreaks, and fire hydrants 7, 33

grain elevators, gravel blanket areas, and guardrails '^> 14, 33

irrigation and drainage systems 15

lumberyards 14, 33

parking lots and under pipelines 7,14, 33

paved highways 39

poison-ivy, poison-oak, and poison-sumac 7, 47

pole yards - 14

racetracks and runways ' » 33

railroads '^» ^^

reinfested areas - 40

roadsides l'^» 1^« ^^

signposts and storage areas T", 33

tank farms, tennis courts, transformer cages, and

trestles '^» l^» 33

transmission towers 7roö~^ß' I7

utility rights-of-way and poles 7,19, 33, 4b, 4(i

weeds in woody plantings 47

Specifications of herbicidal oils ^

Sprayers ^7

aerial ^¿

individual parts of J^

calibration of ^^

aerial %^

ground ^V.

hand |0

power ^"' ^1

cleaning of ^^

ground ;^

boom ^^

boomless ^^

hand 25

individual parts of ^^

mist blowers ^^

special equipment 26

storage of ^2

operation of ^^

regulating volume ^^

regulating droplet size 30

spraying with oils, emulsions, and suspensions, for 28

Spreaders 28

Sterilants 3, 3d, Ob

Storage:

equipment ^^

herbicides ^4

Time of applicairon Jsee also Rates and Dates of

application) 33

Toxicity of herbicides {see also Herbicide index)__ 3, 4, 5

Translocated herbicides 2

Turf 48

management 48

preplanting weed control 48

fumigants 48

nonvolatile temporary soil sterilants 49

selective weed control 50

broad-leaved species 50

weedy grasses 51

Volume of spray 29, 32

Weed species and herbicides for control 57

Weeds {see also Weed species and herbicides for control, table 5) :

annual 2

aquatic. {See Aquatic weeds.)

biennials 2

identification of 6

perennial 2

perpetuation of 2

reproduction of 2

resistant species listed for each herbicide 32

tolerant species listed for each herbicide 32

turf. {SeeTuvt)

winter annual 2

woody. {See Woody plants.)

woody plantings, in 47

Woody plants :

application of herbicides 25, 26, 40

basal-bark 44

cut-surface 44

foliage 41

injection 45

regional rates and dates

basal-bark application, for 44

foliage application, for 41

soil application, for 45

soil 45

stump 44

roadsides, on 46

utility lines, under 46, 47

5!^ U.S. GOVERNMENT PRI NT! NG OFFICE: 196S- -720-753