SUGGESTED GUIDE FOR WEED CONTROL 1969
Ü.S.CE?T. Of AGRICULTURE NATIONIUGWCUITURAL lllRARy MAY 12 196y
CURRENT SERIAL RECORDS
Agriculture Handbook No. 332
Agricultural Research Service UNITED STATES DEPARTMENT OF AGRICULTURE USDA POLICY ON PESTICIDES
One of the most important responsibilities of control which provide the least potential hazard the Department of Agriculture is to develop and to man and animals. When residual pesticides facilitate the use of methods and materials for the must be used to control or eliminate pests, they control of pests. The Department's research, shall be used in minimal effective amounts, applied education, and regulatory programs are expected precisely to the infested area and at minimal to make continuing progress in the never-ending effective frequency. Biological, ecological, or cul- struggle to protect man, his food and fiber sup- plies, and his forests from the ravages of pests. tural methods or nonpersistent and low-toxicity Such protection is essential if the American people pesticides will be used whenever such means are are to continue to enjoy their present high standard feasible and will safely and effectively control or of living, and if this abundance of quality food and eliminate target pests. relative freedom from the hazards of pests are to be In carrying out these objectives, the Department enjoyed by all mankind. will cooperate in the fullest with the other agencies In protecting man, animals, plants, farm and and departments of government, and will seek to forest products, communities, and households develop broad areas of collaboration in establishing against depredation of pests, the Department has the criteria to guide the use and development of vital concern for (1) the health and well-being of pest-control materials. people who use pesticides and those who use Further, the USDA will urge that all users of products protected by their use; and (2) for the pesticides exercise constant vigilance to assure the protection of fish, wildlife, soil, air, and water protection of human health by avoiding unneces- from pesticide pollution. sary exposure of crops, livestock, fish, and wildlife. In keeping with this concern, it is the policy of The Department commends this policy to the Department of Agriculture to practice and to States and local authorities as a guide in their encourage the use of those means of effective pest respective jurisdictions. ^
SUGGESTED GUIDE FOR WEED CONTROL 1969
Prepared by Crops Research Division
Agriculture Handbook No. 332
Washington, D.C. ^P^^^^ ^^^^
For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 70 cents PREFACE
Research in weed control is conducted by the U.S. Department of Agri- culture and certain other Federal agencies, State agricultural experiment stations, and industrial organizations. Many of the most effective weed-control practices resulting from this research are summarized in this handbook as a guide for farm advisory personnel in the various States. Correct identification of a weed species is helpful in selecting and using weed-control suggestions. Providing information on weed identification is outside the scope of this handbook. Descriptive and illustrative guides to the identification of weeds have been published and are available from the State agricultural experiment stations in nearly all States. The successful and safe use of weed-control methods depends on strict adherence to the appropriate treatment procedures. These details may vary between localities because of differences in soil, climate, crop varieties, cultural methods, and weed species. The weed-control methods described here may be considered as a general guide. Specific information may be obtained from State agricultural experiment station and extension service personnel and other local agricultural authorities. All suggested uses of herbicides were registered prior to July 15, 1968, under the provisions of the Federal Insecticide, Fungicide, and Rodenticide Act. The registration of herbicides changes frequently as new information on uses and residues becomes available. New uses are frequently added to labels and old uses are sometimes cancelled. In order to use herbicides effectively and safely, up-to-date labels and instructions must be followed. Because new herbicides and new uses for older ones are being developed constantly, it is important to obtain the latest information from the U.S. Department of Agriculture, State agricultural experiment stations and extension services, and manufacturers of specific products.
FOLLOW THB LABEL
U.S. »ErAHTMENT OF AGmCULTUKE
If herbicides are handled or applied improperly, or if unused por- tions are not disposed of safely, they may be injurious to humans, domestic animals, desirable plants, and fish or other wildlife, and may contaminate water supplies. Use herbicides only when needed and handle them with care. Follow the directions and heed all precautions on the container label. A
CONTENTS
Page Basic principles and methods of weed control 1 Growth cycles and propagation of weeds 1 Plant competition 1 Hand and mechanical methods 2 Flame 2 Herbicides 2 Biological agents 2 Impact of weed control on crop production 2 Precautions for safe use of herbicides 3 Properties of herbicides ^-- 4 General considerations in use of herbicides 4 Purchasing herbicides _-__ 4 Calculations for herbicide applications 13 Mixing spray materials 14 Application equipment _ 14 Calibration of application equipment 15 How to determine per-acre output of sprayers 15 How to determine output of spreaders ^— 17 Effect of weather conditions on herbicide applications 17 Weed control in field crops 1^ Weed control in horticultural crops 36 Vegetables ^7 Deciduous tree fruits and nuts 40 Citrus and subtropical fruits and nuts 42 Small fruits 43 Ornamental plants 45 Weed control in horticultural plant beds and nurseries 4b Weed control in greenhouses 47 Weed control in forage crops, pastures, and rangelands_ _ _ 47 Weed control in lawns and other turf areas___ 52 Weed control in noncropland 54 Construction aids 54 Cultural, biological, and mechanical control 54 Control with herbicides 55 Control of aquatic weeds ^ Construction aids ^J: Management practices ^ Hand and mechanical control ^ Biological control ^1 Chemical control ^1 Appendix—Herbicide tolerances for crops ^5 Crop index ^* Weed index ^^ LIST OF TABLES
Table 1 Chemical, physical, and biological properties of herbicides 5 2 Weed control in field row crops 1§ 3 Weed control in close-drilled field crops 27 4 Control of perennial weeds in cropland in fallow periods or by spot treatment 3^ 5 Weed control in vegetables 37 6 Weed control in deciduous tree fruits and nuts llllllllll I 40 7 Weed control in citrus and subtropical fruits and nuts ' 42 8 Weed control in small fruits 44 9 Weed control in ornamental plants 45 10 Weed control with soil fumigant herbicides in horticultural' plant beds and nurseries 4*7 11 Weed control in forage crops, pastures, and rangelands ~_ ~ ' " 48 12 Weed control in lawns and other turf areas 53 13 Weed control in noncropland (ditchbanks, fence rows, "floodways^ mdustrial sites, and railroad, highway, and utihty fine rights-of- way) rß 14 Control of aquatic weeds (irrigation canals, drainage ditches, streams, lakes, ponds, reservoirs, marshes) .' 62 SUGGESTED GUIDE FOR WEED CONTROL 1969
Prepared by CROPS RESEARCH DIVISION, Agricultural Research Service ^
BASIC PRINCIPLES AND METHODS OF WEED CONTROL
Weed control is an integral part of the overall burdock, wild carrot, and mullein. They often management program for crop production, grazing can be controlled by cultivation or timely mowing. land, lawns, gardens, irrigation and drainage Perennials Uve more than 2 years. Many have systems, and other crop and noncrop areas. For several methods of reproduction in addition to greatest effectiveness and economy, weed-control seeds. These include bulbs, tubers, corms, lateral methods must be based on the basic principles of roots, rhizomes, and stolons. Most of these plant ecology and physiology, soil fertihty, soil- organs have buds and store food for overwintering water relations, and plant growth. Effective and reproduction. Several provide means of weed-control methods and materials include crop vegetative spread. Many perennial weeds are rotation, grazing, cultivation, mowing, flame, and difficult to control and require intensive and the use of herbicides, surfactants, and biological persistent effort. Common examples are Canada agents. The effects of chemicals and biological thistle, cattail, field bindweed, johnsongrass, and agents on human beings, livestock, fish, and wild- nutsedge. Unlike most annual plants, killing the life must be considered. All these principles and top growth of a perennial once does not usually phases of vegetation control are considered in the prevent it from surviving and producing a new preparation of this handbook. top growth from food in the storage or reproduc- tive organs. To prevent this vegetative reproduc- tion, the supply of stored food must be greatly GROWTH CYCLES AND PROPAGATION OF depleted by repeatedly destroying the top growth, WEEDS roots, and reproductive organs or greatly altering the physiological processes with herbicides. A weed is any plant that grows where it is not desired. Weeds, like other plants, are classified PLANT COMPETITION by growth cycle as annuals, biennials,, and perennials. Algae and some other aquatic plants Competition of desirable crops or plants with have a shorter life cycle. Annuals mature in undesirable plants frequently provides effective one season and are nearly always propagated by and economical weed control. Careful selection seeds. Examples are pigweed, crabgrass, and of adapted and desirable species or varieties and common ragweed.^ A variation of the true annual maintenance of optimum soil fertility and cultural is the winter annual that germinates in the fall conditions for their maximum growth are impor- and matures seed the next season. Examples tant. Mowing, pasturing with Hvestock, spraying are cheat, pennycress, shepherdspurse, and wild with selective herbicides, liming, fertihzing, or barley. Most annuals are prolific seed producers, other means of altering the environment to favor and seeds of many remain viable in the soil for the desired species over weeds may be necessary many years. Even though most annual weeds for the most satisfactory results. Usually the are easily killed by mechanical or chemical means, desired competitive crop must be planted. the enormous accumulation of seeds in the soil Occasionally a mixture of desirable and un- makes their control difficult. desirable vegetation already established on native Biennials require two growing seasons to ranges, ditchbanks, fence rows, or other nonculti- complete the reproduction cycle and are propa- vated areas can be favorably altered by repeated gated by seeds only. Common examples are apphcations of selective herbicides. Under such treatment the resistant desirable species become dominant and the susceptible undesirable species 1 The technical information in this publication was are gradually eliminated. The elimination of compiled and reviewed by L. L. Danielson, W. B, Ennis, deep-rooted perennial weeds or other aggressive Jr., W. A. Gentner, J. T. Holstun, Jr., D. L. Klingman, species often necessitates the use of drastic and W. C. Shaw, F. L. Timmons, and associated personnel of the Crops Protection Research Branch, Crops Research frequently expensive chemical or mechanical Division. Helpful suggestions were made by reviewers methods. Thereafter, desirable species can be in the Pesticides Regulation Division and the Federal planted and suitable conditions provided for their Extension Service of the U.S. Department of Agriculture. effective competition with surviving or reinvading 2 Source for common names of weeds is 1966 list of Weed Society of America (Weeds 14, No. 4, pp. 347-386). weeds. AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE
HAND AND MECHANICAL METHODS humans. However, safe and effective herbicides are available for controlling many weeds growing Numerous effective herbicides and improved in various environments, including cropland, methods of appUcation have replaced many less rangeland, gardens, lawns, ditchbanks, and other effective hand and mechanical methods of weed noncrop areas, and in irrigation, drainage, navi- control. However, hand and mechanical methods gable, and potable waters. Because of the many are still necessary or advantageous in many situa- factors and principles involved and the dynamic tions. Hand weeding of flowerbeds, small vege- nature of research on herbicides, information about table gardens, and other small-area plantings chemical weed control is rapidly increasing and sensitive to herbicides is often the safest and most new recommendations are continually replacing satisfactory method. Mulches also aid in weed old ones. control. Improvements in tools used for cultivat- Suggestions for apphcation rates of herbicides ing, mowing, burning, and ditch cleaning and in are based on the active ingredient or acid equiva- other machinery needed for vegetation control lent contained, and not on the total weight of the have coincided with improvements in chemical product. methods. Judicious use of such equipment in seedbed preparation, cultivation of crops, and mowing in noncultivated areas may cause weed BIOLOGICAL AGENTS seeds to germinate, destroys successive crops of weeds, and prevents weeds from producing ma- Only limited attention has been given to con- ture seeds. Even the most effective chemical trolling undesirable plants by using insects, plant methods frequently must be supplemented by disease organisms, and other natural enemies. hand or mechanical weeding to remove surviving Research is now underway to discover and de- weeds and to prevent future spread by seed or velop effective and safe biological agents to con- other plant parts. trol such weedy species as alligatorweed, water- hyacinth, submersed aquatic weeds, Scotch broom, halogeton, cactus, tansy ragwort, puncturevine, FLAME gorse, and St. Johnswort. One noticeably success- ful biological control agent in the Northwestern Flame is used effectively for weed control in some situations. Several types of burners are States is the beetle Chrysolina spp. This insect is native to Europe but was introduced from available. Those used for nonselective control of Australia to the United States to control St. weeds as on ditchbanks produce a relatively large, Johnswort. Research on biological control of varying flame pattern. Those used for selective control of weeds as in cotton and corn produce a weeds is being increased and probably will be emphasized considerably in the future. relatively small constant flame pattern that can be confined to definite areas in or between the rows. Some specialized burners are designed to IMPACT OF WEED CONTROL ON CROP trap and retain the generated heat momentarily PRODUCTION in the weed area. Fuels most commonly used are propane, butane, Weed-control principles, methods, and practices and mixtures of these two petroleum gases. have an important impact on all phases of crop Either a vaporizer or self-energizing design of the production. New chemical, cultural, mechanical, burner usually increases the efficiency of the biological, and combination methods of weed combustion. Fuel oil, kerosene, and other petro- control affect crop choice; the variety to use; leum liquids are also used. seedbed preparation; method of seeding; seeding rates; row spacing; plant spacing in the row; HERBICIDES plant populations; fertilizer practices, including type, time of application, and placement; culti- Since 1950 thousands of chemicals have been vation; irrigation practices; harvesting; seed- evaluated for effectiveness as herbicides and more cleaning operations; erosion control; fallow prac- than 100 of these have been recommended for con- tices for weed control; disease- and insect-control trolling one or more weeds. The effectiveness of practices; pasture renovation; pasture and range herbicides on susceptible species is affected by management; clearing new lands for crops or stage of growth, soil organic matter and pH, fer- pasture; forest management; the utilization of tiUty, and texture; rainfall and irrigation; water farm water resources for irrigation and recreation ; pH and chemical content; temperature of air and and the maintenance of drainage ditches, ditch- water; light intensity; and other soil, water, and banks, irrigation canals, and farm roadsides. climatic factors. Crop and weed plants vary Equally important are the significant effects crop widely in their responses to different herbicides. manageraent and production practices have on Some herbicides may kill fish, some may injure the choice and effectiveness of weed-control livestock and wildlife, and a few may affect methods. SUGGESTED GUIDE FOR WEED CONTROL 19 69 PRECAUTIONS FOR SAFE USE OF HERBICIDES
All chemicals described in this handbook, wear goggles where label instructions specify. especially when used on raw agricultural crops 5. Avoid spilling herbicide concentrate on your as defined under Public Law 518, should be appUed skin and keep it out of your eyes, nose, and in accordance with the directions on the manu- mouth. If you spill any on your skin, wash it off facturer's label, as registered under the Federal immediately with soap and water. If you spill it Insecticide, Fungicide, and Rodenticide Act. on your clothing, launder the clothing before Specifications with respect to crop, amount of wearing it again. chemical, and time of application should be 6. Handle flammable chemicals with care to strictly observed. avoid ignition from friction, sparks, or contact Many herbicides are irritating or potentially with combustible materials. dangerous, but they are not hazardous if used 7. Avoid contaminating potable water supplies properly and if recommended precautions are with herbicides. observed. Most herbicides have a low acute oral 8. Dispose of empty containers and surplus toxicity, but a few are highly toxic to humans, herbicide solutions by burial at least 18 inches livestock, and wildlife, and some are toxic to deep in a level, isolated area where they will not fish. The relative degree of acute toxicity to contaminate water supplies. warmblooded animals is given for most herbicides For livestock— listed for weed control in table 1. In the following 1. Prevent Hvestock from grazing in areas data the LD50 ratings (lethal dosage that kills where herbicide sprays may have increased the 50 percent of the experimental animals) are classi- palatabiUty of poisonous plants or increased the fied as to acute oral toxicity: amounts of nitrate or other chemicals of certain Acute oral tox- plants to a toxic level. icity LD50, mg. Lethal dosage for 2. Prevent livestock from drinking water that Class per kg. 150-lb. man has been treated with an herbicide during the Highly toxic 50 and below___ Few drops to 1 tea- spoon. time after treatment prescribed on the label. Moderately toxic. 50-500 1 teaspoon to 1 oz. For wildlife and fish— Mildly toxic 500-5,000 1 oz. to 1 pt. or 1 lb. Nontoxic Above 5,000_ _.- 1 pt. to over 1 qt. 1. Avoid overdoses and spillage of herbicides in or near streams, ponds, and lakes or in areas All LD50 values in table 1 are based on a single frequented by wildlife. dose of material orally administered to animals, 2. A few herbicides are toxic to fish and wildlife. followed by observation of the treated animals for Do not apply herbicides that do not have an ap- a definite period. However, these findings do not proved label for such use to canals, lakes, ponds, indicate the possible hazards that may arise from or streams. skin contact or inhalation of the substances. 3. Consult Federal or State game and fish Likewise, these data do not accurately predict the departments for advice if a proposed herbicide toxicity of a formulation that may differ accord- application might endanger wildlife or fish. ing to the solvent or diluent used. For desirable plants— The following general precautions should be 1. Avoid spraying when and where drift of fine observed in applying herbicides : spray or volatiHzed fumes is likely to contact For humans— nearby sensitive crop or ornamental plants. Use 1. Read the label on each container before spot treatment control of weeds in lawns if they using the contents. Follow instructions; heed all are not too numerous. cautions and warnings. Store in closed, well- 2. Reduce drift hazards by using low dritt labeled containers out of the reach of children and formulations, amine or low-volatile esters of pets, and where the herbicides cannot contaminate phenoxy herbicides, low spraying pressures, and food or water. large volumes of coarse sprays and by spraying 2. Avoid inhaling vapors, dusts, or spray mists. when wind is low in velocity and blowing away Use a mask when specified on the container label. from nearby sensitive plants. Do not spray when 3. Avoid repeated or prolonged contact of temperatures exceed 90° F. i • • j herbicides by the skin. Some individuals are 3. Avoid applying a soil sterilant herbicide to hypersensitive to certain chemicals and must be the foHage or over the root zone of a tree, shrub, especially careful to avoid allergic reactions. or other desirable plant where leaching the chemi- 4. Wash hands and face thoroughly with soap cal into the soil may result in death or injury of the and water after each use of an herbicide. Do not plant. eat, drink, or smoke until you have washed your 4. Avoid applying herbicides or cleaning out h^i^^s and face. Wear synthetic rubber gloves and appHcation equipment on sloping bare ground, AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE
pavement, or other areas where the herbicide may of activated charcoal in 10 gallons of water con- be carried by surface runoflF to valuable plants taining household detergent), followed by a rinse downslope. of clean water. 5. Avoid using herbicide sprayers for other No matter how well it has been cleaned, a purposes on crop or ornamental plants that are sprayer that previously has been used for applying sensitive to herbicides until the equipment is phenoxy herbicides should not be used to spray thoroughly cleaned. Clean the equipment with cotton, tomatoes, grapes, and many ornamentals warm water and detergent, followed by 12 to 24 highly sensitive to 2,4-D and other phenoxy or hours of soaking with a solution of one part of similar growth-regulator herbicides. household ammonia in 100 parts of water, or rinse 6. Do not store herbicides near seeds, bulbs, the sprayer for 2 minutes with a 0.25-percent fertilizers, insecticides, fungicides, or other farm suspension of activated charcoal (one-fourth pound chemicals and supplies.
PROPERTIES OF HERBICIDES
Descriptions of the chemical, physical, and mercial formulations are given as a convenience biological properties of herbicides mentioned in in determining the kinds of application equipment this handbook are given in table 1. The herbicides needed in using the herbicides. Brief reference is are designated by their common and chemical made to certain important weeds controlled by names. Their acute oral toxicity to warmblooded each herbicide, some of the practical uses in crops, animals is indicated by the LD50 rating given in specialized methods of application, and specific terms of milligrams of herbicide per kilogram of toxic or persistence characteristics. Specialized, body weight of rats, except where other animals accepted uses of the herbicides in various crops are specifically named. The basic chemical refer- and in noncrop weed situations are described in ence material used to calculate application rates detail under the appropriate headings on pages is shown for each herbicide. The kinds of com- 18-64.
GENERAL CONSIDERATIONS IN USE OF HERBICIDES
PURCHASING HERBICIDES active chemical. The containers for all commercial herbicides have labels that state the amount of Formulations active chemicals contained in the particular Most herbicides are usually purchased as a product. This is expressed in percentage of active commercial formulation that contains the herbi- ingredient, acid equivalent, or phenol equivalent cide and can be (1) dissolved, emulsified, or for solids and in pounds per gallon for liquids. suspended in a liquid carrier, (2) distributed dry Where a formulation contains a mixture of herbi- by a spreader or by hand, or (3) injected into soil cides, the amount of each herbicide is given on for vaporization and fumigation. Often an emul- the label and should be considered in determining sifier, spreader, sticker, or other surfactant is the relative value of the mixture. added to facilitate dilution and adhering capacity Acid equivalent is commonly used to express or to increase wetting of plants. Many formula- the active chemical in dalapon and the phenoxy, tions contain inactive fillers that serve as diluents benzoic, and picolinic acid herbicides, such as only. For example, there may be 2, 3, 4, or 6 2,4-p, silvex, 2,3,6-TBA, and picloram. Phenol pounds of active herbicide in a gallon of liquid equivalent is used to express the active chemical formulation weighing as much as 10 pounds or 4, in dinitrophenol and pentachlorophenol deriva- 10, 20, 50, or 80 percent of active chemical in a tives. For most other compounds the active granule, pellet, or powder formulation. chemical content is expressed as active ingredient. Usually the concentrated formulations are more Active Chemical Content economical to use than diluted concentrations when the herbicide is applied in a spray. For Although the carrier components contained in example, 2,4-D formulations that contain 4 herbicides, such as emulsifiers, solvents, and other pounds of acid equivalent per gallon nearly always adjuvants, often affect problems encountered in cost less per pound of 2,4-D than formulations mixing and spraying and on weed-control results, containing only 1 or 2 pounds of 2,4-D acid the economic value of an herbicide is largely equivalent per gallon. On the other hand, herbi- dependent on the relative amount of phytotoxic cides to be broadcast dry in granules or pellets chemical that is contained per gallon or pound. may require diluted concentrations as low as 4, One of the best guides to use in purchasing a 10, or 20 percent to permit precise and uniform commercial herbicide is the price per pound of application. SUGGESTED GUIDE FOR WEED CONTROL 19 69
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OF AGRICULTURE -^^ tí • 72 CO I I, ^3o ütí o<3^ .a .2 ^ «r £ ¿a 03 4^ 03-^^^^^ s <-¿ CO 4J (^ I ;H ü tí OH °3 03 O tí tí T3 S ^ ^ ;3 ü ^ tí 03 03 O^ PM c3 02 PH'' m o 02 PH PH d" 5^ O PH o o O fe fe "^ O) tí -^ 0 03 o o -^ +^ ^-1 ;-( tí > H 03 c3 ^ tí ''S PH g PH 2 03 03 'tí tí '73 tí c3 tí tí tí^ tí cr 03 O 03 ü 03 tí ^ (-1 ;H tí ^ tí Oí fe s feo 03 43 03 tí 03 OH OH OH "^ OH^ OH 03 t 03 '^ jtí tí '-+3 ^^ ^ O üO 03 o oa O ÜO 03 O O o o o o o O P o ^ ^ Ö O o O o o CO I I '-es o o o O o o o o o o o o CO o o CD CO o CO o CO o o 1-H 38-51 7,000 CO ¿ . ¿ 03 .4. tí 03 H c3 • 03 tí ü O ;H 6 03 I 03 acid hept o:tí is (t T5n3 Ig tí ití -^ .^.2 OH OH O 03 sa 03 O 1^ OH g»l r2-2 O '^ T* OH ^3 a; OH ^ I ^ tí ¿ I +3 O a > 03 •r (M . -73 o^ fH <13'^ < -^.^^ . 43ci¿| tí A e glycol cyclo[2.2. icarboxyl a oacetate) 3^00• Í5 tí í tí :$; i 03 SëS-V .o - >;í tí -^f T3 tí T3 -r^-^ o3co 03 o >,^ X ^- >^ 03 S^5-2¿'S sí rtí ;-! ©•3 ¿o, ^ Ontí CO ^ o oc^ £3, 03 Oncvf 03 OH CO fO TíH" Oí (M c^ oí" .22 c3 Ö tí O S s c3 o PLH O Ü f^ o pq o tí tí ^ H Ti o c3 tí er tí X2 tí tí o í/2 O tí PH U 03 03 PL, S Q H W W ^ fe fe SUGGESTED GUIDE FOR WEED CONTROL 19 619 ü tí ü o CD I 4^ O -Sog tí "^ tí tí tí ^ fe tí Í-I o «DO) ♦» O) "^ es I ^ 03 ü I—t ^ ¿Jig bC bßbß F—( 0^ ^ S 03 ft o c3 T3 bß tí (D -g O) O) 03 Ö S ^ tí--;3 ce ^«-^ tí ^ O Oí »r o tí -( ?á •- 02 - 03 ü ÇH (D T3 CO o 02 -4^ t> r^ o '=^ o3 tí 03 O I* S O) S S tí g O tí 'D CO T3 . ^ rtí '3^ (D d (X) O) tí ^ -^ .tí tí 03 Q tí O) -^^ . 111„ ,^. . jD O) CO CO o3 Ü ■ >^ ft g Ö. g o; . „ CO o3 P.. ^'t;^L,aQtí^2tí bC T3 Ö Cl bß tí ft ^ SS-^ ^ bC œ _j c3 tí o ?H ^ tí O3T3 tí ¡ 03 «D tí t» . ^ ^ ^ao^-^ g ^ c3 O Ö 5í ^ tí 0 •=1 O tí .^^'^ Ö 2 •'^ '-I tí'sja %^ "^ bß.S-S d o3 PM PH 02 c3 03 oT PL, PH PH 02 f^ &1 O O &: ^ ^ O w o tí O O rtí tí tí O tí :tí § a tí o o o o o o O o ¿ o CO o o O o o o o o o O CO "^ o (N O s o O o CO f2 CO (N rH 00 tí =3" I '^ I Go , i-H O A a I V ¿ 2<¿ ^ ft o o3 0^(M O .a 'S -r '^ c3 ^ tí CD^ ^ 03 «2 ptí ó "^ TD U -)J A 0) >^ . ^. tí tí^ 2 .^ tí c3 ü Tti c3 -tí-fe■ a Ö -tí^ o Ö CD 0 03 o o ^ ptí ^ 4 a^g^ ^ 03-tí T-H ë I 03 a CO'rH 3 > 2.a -t^ -tí A CO o tí »^ ""^ ^^ ^•—^ I CO "^ T3 O (Dq3 9 Ö ft t-i tí O) I CO tí çH ^ >. 2^ .a^ 0 >>tí ü X Ortí T3 c3 coíJT^o Q^ tí _^ 03 tí-^ O I t>5_tí ;H rH 'd « tí o O >^ tí03 >. cr PLH Ä tí 03 o PL, u o O O w o 03 S ^ ^ ^ PH 10 AGRICULTURE HANDBOOK 33,2, U.S. DEPT. OF AGRICULTURE -o «2 TO CO 03,+H 52 « (H (H o3 X O) ^ bß tí ^ ^ 50 , o o^ tí T3 O o3 0) o3 O o i; 2 « ^ M % o tí °'^ Oí >H tí ¡^ 02 a Oí'O ^ 02-^ 03 03 ^ c3 .^ -^^ s ►'^ bß O CT' O OQ '-•35. ?H QQ ^ ^ «4-1 (D ^ 02 ^^ 'S «2 tí2^ o 2^ "^S o ^ ^ fH bß g bßg bß g ^TJTS Oí "•^ tí-^ ^ 03 a;t! 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O o, CÙ o o o o o ü o o o o O o o o o o o :=; Oo o o lO o I o »^ o o o o o o o o (£) i> o o o o CO o o o CO o o ^•^ ^. o A CO T-l rH 2o O ^ fe 1 T3 CO flí O o I >> . 4^ -üq o *C 'S t^tí -ö o ^ Ä ^ 03 o >» -».3 tí ^ S o:tí rC X5 O .2 § O (-1 4-3 i tít^S >> tí T! tí •73 o3 í>>tí -52 •>-; 13 r^ /T 03 CO 2 2 03 § O o ^.a'3 >>o3 u ë -£§ a o t^gco o^ OHX5 O ^3 S.S BZ CO I« o, c5 3 tí O ^ 03 o3 o Ti o tí T3 O 03 O o o tí H H O} 12 AGRICULTURE HANDBOOK 33 2, U.S. DEPT. OF AGRICULTURE Ö rn (7^ > T3 ^-j ^ Oí bß al (D ^ tí ses. tile tí tí J œ 02 03 tí ^ 03 c3 OJ m '^ ^ g So a a g.S ^ Î3 tí ta 03 ^ g ä § o; 0 tí '-^ S § tí o vr^T3 O X2 02 (M ^ 02 ^ ^ ^ bß 0) m o if CO .2 03 ^ tí 0^ tí +3 tí I -í3 o a rr ^ > o; tí 0) CI) 03 ft 03 tí bß 03 a ^.a-^ T3 0 not and w ^^-^ minati tí âï a bf) 03 a &^ O U ^r.'^ 43 Stíeg ^ hi ^ o bCg ft Pi 3 £ £ tí f-i O) ES 2 tí— So 4^ S ^ -2 --' 3 '-' tí tí l> O 0) o 03 !^ >% ;_, ö tí o3 -tS bß.- ctí i T3 O O 53 ^ ,2 -O o a^^ tíT3 7) a a^ ^ O tí O tí .. ^ OH^;tí W í-i a X5 T3 --H T3 o; o O 03 'o'a o «3 ^^ ^H GO •S a ^ ^ 0 03 .-tí^-H c3 leH 03 f-( S tí bß 2 03 03 tí O tí " tí--^ c3^ §^ pq ^ 03 tí 0) 0) 02 oPn ^:tí o o o o 5ïi o o I I o o O O o d^tí^^ o o lO o o o"*^ o CO 00 CO 3 03 o o tí o X tí o 03 ,^i ¿1 tí hn 03 O) LT O M.^ o 02 p . m o ;3 o3'g^^-3 PÔ ..^ cS ft Q 7^.^-5-I -^^ ..V .^ tí -«rH 03 OXi ce O) ^"^ c3 tí 73 o Tí I 'C %, -^ ^ (M ^ O 73 03 lili73 bß S tí oœ •- o : PLH H PQ H H d^ií o tí O Q n 9 ^^ CO 4 ^ ^ i> tí c Volatility of some herbicides are also useful in controlling Another important consideration in purchasing aquatic weeds and weeds in noncropland areas, 2,4-D, 2,4,5-T, or other phenoxy herbicides for including ditchbanks, rights-of-way, and industrial certain weeds and special situations is the type of sites. herbicide formulation—amine or high-volatile or Numerous experiments have shown that gran- low-volatile ester. When vapors from the herbi- ules and sprays of many herbicides are equally cide are likely to injure adjacent crops or plants, effective in controlling germinating weed seed in an emulsifiable acid, amine salt formulation, or a the soil. Each herbicide, whether used in spray low-volatile ester should be used. Esters of or granular form, requires certain specific condi- 2,4-D and 2,4,5-T are classified as high or low tions of climate, soil, and application technique volatile according to the degree of vaporization for best results. Recommendations prepared by that occurs. In general, methyl, ethyl, isopropyl, weed research specialists in State agricultural butyl, and amyl esters are considered highly experiment stations and by the individual manu- volatile. The butoxyethyl, butoxyethoxypropyl, facturers of granular herbicides outline these ethoxyethoxypropyl, propyleneglycolbutylether, necessary conditions. isooctyl, and other high molecular weight esters are low volatile. CALCULATIONS FOR HERBICIDE APPLICATIONS Granular Herbicides Granular herbicides are formulated for applica- Recommended rates of herbicide applications tion as dry granules. They are applied with are stated in ounces or pounds per square rod, specialized granular pesticide spreading equipment 1,000 square feet, or acre where the area to be or modified fertilizer spreaders. treated can be measured. Where spot spraying of Granules are prepared in several ways. Some individual or small clumps of plants is necessary herbicides are impregnated on granules of clay, or where dense foliage of certain aquatic plants, vermiculite, or crop residues, such as corncobs, by brush, or trees is to be thoroughly wet, the con- spraying, dipping, or exposing the granules to centration of spray is usually recommended in herbicide vapors. Granules are also prepared by pounds of active chemical per 100 gallons of water mixing an herbicide with finely ground clay or or oil. To control submersed aquatic weeds, the fertilizer salts, and particles are formed by rate is usually expressed as pounds of active extrusion or prilling. chemical per acre-foot of water or as parts per One of the most important properties of granular million by weight of water (p.p.m.w.) in the area herbicides is physical selectivity or the tendency treated. for particles to bounce off foliage and other plant 1. To determine the amount of herbicide re- parts to the soil or to settle to the bottom of ponds, quired for submersed aquatic weeds, use the lakes, and other bodies of water. This physical following data and calculations: selectivity enhances the chemical selectivity of 1 acre-foot of water weighs 2,722,500 pounds herbicides used on growing crops or on submersed 1 p.p.m.w. = 2.7 pounds of active herbicide in 1 aquatic weeds. Sprays are often intercepted by acre-foot of water crop foliage and their effectiveness in killing (1) Pounds of herbicide = pounds per acre-foot germinating weed seeds in the soil is reduced. (area in acres X average depth in feet) Granules tend to bounce off and sift down through the foliage to the soil where they are needed. Example : Granular herbicides are of special interest in the Rate=4 pounds per acre-foot growing of horticultural crops, because their Area=2.5 acres physical selectivity helps to broaden the use of a Depth=3 feet (average), or 7.5 acre-feet few effective herbicides to cover a relatively large Then pounds of herbicide=4X7.5 = 30 pounds number of crops. They have therefore been used required rather extensively in horticultural crops after clean (2) Pounds of herbicide=p.p.m.w. X acre-feetX cultivation. Granules also fill a specific need in 2.7 transplanted crops, where preemergence herbicide Example : treatments cannot be used. As a matter of con- Rate=1.5 p.p.m.w. venience, granular herbicides have also been Volume=2 acres, 3 feet deep (average), or 6 extensively used in preplant soil-incorporated and acre-feet preemergence treatments of horticultural crops. Then pounds of herbicide= 1.5X6X2.7 = 24.3 Because of the scarcity in many areas of clean pounds required water supplies for spraying and the need for extra 2. To determine the amount of herbicide for- labor and equipment for water hauling, granular mulation required per acre, per acre-foot, per herbicides have been used in several field row 100 gallons, or for a total area, use the following crops and in ranges and pastures. Granular forms calculations : 320-446 O - 69 - 14 AGRICULTURE HANDBOOK 33.2, U.S. DEPT. OF AGRICULTURE (1) For liquid formulations— Never pour the liquid concentrate or dry herbi- Rate or amount required in pounds ^ . , cide formulation into an empty tank. Either fill -ñ Í 7-i—1 . . 1 —Î1— = gallons req uired rounds oí herbicide per gallon the tank half full with water, add the herbicide, agitate, and complete the filling or start filling Examples : and add the herbicide gradually as the filling is Rate, 2 pounds per acre ^ _ „ T-^ ^ *^-^n =0.5 gallon continued. Agitate or stir until all solid material 4 pounds per gallon is dissolved. If a water-soluble powdered or crys- Concentration, 4 pounds per 100 gallons , ^ talline form of herbicide is to be used with a —f *Vi ^ =1 gallon 4 pounds per gallon liquid herbicide, dissolve the solid material in water first and then add and mix the liquid. If Amount required, 24.3 pounds 12.15 gallons 0Ü is to be used in an oil-water or invert emulsion, 2 pounds per gallon premix the emulsifier and the oil-soluble herbicide (2) For granule, dust, or pellet formulations— with the oil in a separate container and then add Use the same calculations as for liquid formula- slowly to a partially filled tank of water with tions, except use pounds of active herbicide per constant stirring or agitation. Circulate the mix- pound of formulation (percent-î-100) instead of ture until it is uniformly white before using. pounds per gallon. Agitate suspensions of water-dispersible powders Examples : and oil-water emulsions constantly or frequently during spraying to maintain a uniform spray Rate, 2 pounds per acre _ , mixiture. Use the spray mixture within 1 or 2 0.5 pound (50-percent material) ^ days, because some herbicides lose strength or the Concentration, 4 pounds per 100 gallons mixtures deteriorate on standing. = 8 pounds 0.5 pound (50-percent material) Amount required, 24.3 pounds _.(y. ^ i APPLICATION EQUIPMENT 0.20 pound (20-percent material) ~" * P Results from using herbicides depend largely on how well or how poorly they are applied. This, in turn, depends on the suitability of the MIXING SPRAY MATERIALS equipment for the particular situation and the care and skill with which the operator utilizes the When the capacity of a spray tank is not known equipment. Suitable equipment has been devised or adequately marked to indicate the number of for nearly every situation requiring herbicide gallons at different levels of liquid in the tank, applications. the best procedure is to set the sprayer or tank Ground sprayers include (1) hand sprayers of on a level base and gradually fill the tank with various types suitable for treating small patches, known quantities of water. As the water is added, inaccessible areas, fence rows, and spot spraying; the level of water should be marked in number of (2) boomless power sprayers—nozzle-cluster gallons or fractions of a gallon on the side of the type—adapted for spraying roadsides and ditch- tank or on a calibration rod or stick held per- banks, under utility lines, and along fence rows; pendicularly in the center of the tank. Carefully (3) power sprayers with tractor or truck-mounted measured markings are very useful in determining solid or sectional booms suitable for spraying the volume in partially filled tanks. field, pasture, range, and turf areas or for roadside To approximate quickly the capacity of a and ditchbank spraying; (4) power row-crop sprayer tank (all measurements in inches), use sprayers with various single and multiple nozzle the following calculations : arrangements or other devices for placement spraying; (5) power sprayers equipped with hoses, Rectangular tanks: Capacity in gallons=lengthX hand booms, or adjustable spray guns for applica- widthXdepthX 0.00439 tion of foliage, basal, and stump treatments for Example: brush control, spot treatments, and spraying 60X36X30X0.00439=284.47 gallons around structures; and (6) power-driven mist Cylindrical tanks: Capacity in gallons=lengthX blowers, ranging from hand-carried to truck- square of diameterX 0.0034 mounted equipment, designed for dispersing con- centrated sprays in finely atomized form at low Example: volumes per acre and adapted for covering vege- 60X (36X36)X0.0034=264.38 gallons tation rapidly with a minimum of solution in Tanks with elliptical cross section: Capacity in inaccessible areas where wind drift can be utilized gallons=length X square of (short diameter+ to advantage and where a hazard to desirable long diameter)-î-2X0.0034 vegetation does not exist. Example : Aerial sprayers of many types have been developed on fixed-wing aircraft and helicopters. 60x(^^y^Yx0.0034=::183.6 gallons They have several advantages for application of SUGGESTED GUIDE FOR WEED CONTROL 1969 15 herbicides at low volumes for many large field, discharge from each nozzle in a separate container, rangeland, aquatic, and right-of-way areas when such as a calibrated baby bottle. If the discharge and where spray drift is not a hazard. varies widely, replace all worn nozzle tips that Suitable spreaders, ranging from hand-operated give a much larger discharge. to power-driven and tractor-, truck-, or boat- 2. Place the sprayer on level ground and fill rQounted types, have been developed for most the spray tank completely with water. Adjust situations requiring application of granular or the spraying pressure as you will use it in the field. pellet herbicide formulations. 3. Drive exactly one-eighth mile (66Ó feet) in See U.S. Department of Agriculture Handbook a field or along a road, ditchbank, or other area 269, ^'Herbicide Manual for Noncropland Weeds,'' to be sprayed at the speed you will use when or publications of the State agricultural experi- spraying—usually 3 to 5 miles an hour. Measure ment stations or extension service for.more detailed from where the spraying begins. Mark the notch information on herbicide application equipment, in which the throttle is set and keep it there including tanks, pumps, booms, nozzles, hoses and when spraying. fittings, power sources, pressure regulation, droplet 4. Shut off the spray, return to the original size, specialized accessories, and other features of spraying position on level ground, and measure selection, adaptation, and use of application the water required to refill the tank (a quart jar equipment. is satisfactory). For information on aerial equipment, see U.S. 5. Calculate the output as follows: Department of Agriculture Handbook 287, ''Aerial Number of quarts used X16.5 ^ Application of Agricultural Chemicals.'' ^f'-jTT—£-^ TTr~'—Í—7= gallons per acre Width 01 spray swath m leet ° ^ CALIBRATION OF APPLICATION Example: EQUIPMENT Water used=6 quarts Spray swath width=20 feet The type and operating condition of application equipment for herbicides are important for Then — =^4.95 gallons per acre efficient chemical weed control. This is especially true of sprayers. Accurate appUcation of the 6. Divide the number of gallons the tank holds desired rate and uniform distribution of spray by the number of gallons your sprayer applies per solution or dry material are essential requirements acre (approximately 5). Multiply the number of for good results. A sprayer must uniformly acres one tankful will spray by the amount of distribute any quantity from 5 to 100 gallons or herbicide to be used per acre. This gives the more per acre, since various weeds and locations amount of herbicide to be used for each tankful. may require a wide range of dilution for proper Example : plant coverage. Sprayer or spreader output should Tank capacity=55 gallons be determined for each particular treatment Outputs 5 gallons per acre operation. Desired rate of herbicide=2 pints per acre A good method of calibration is to make initial 55 Then—X2=:22 pints, or 2.75 gallons, of adjustments to suit the machine and job require- o ments, and then make a trial run to determine the herbicide actual output of the machine. The herbicide spray mixture then should be prepared accord- In some row crops only narrow bands are ingly. The calibration should be repeated fre- sprayed, centered over each row, such as in pre- quently to check nozzle orifice wear and other emergence treatments of cotton or soybeans. factors affecting performance. This is especially When treatments are made in this manner, the important when wettable powders or abrasive rate of treatment is in terms of the area treated sprays are used. and not per acre of actual crop. Thus in cotton with 36-inch row spacing, if a 12-inch band is HOW TO DETERMINE PER-ACRE OUTPUT treated at 1.5 pounds per acre (based on the area actually treated), the amount of chemical per acre OF SPRAYERS . 12 of cotton is —XI.5=0.5 pound, There are many methods of calibrating a oo sprayer. One method is given for caHbrating Hand-Type Boom Sprayers each of the following types of ground and aerial sprayers. 1. Fill knapsack or other hand sprayer to a marked point with water and spray while walking Power Sprayers—Boom Type at a steady pace, maintaining a constant tank 1. Check to see whether all nozzles are dis- pressure for a distance of 330 feet. Multiply 330 charging uniformly by spraying water through by the width of swath in feet and divide by them at a uniform pressure and catching the 43,560 to obtain the fraction of an acre sprayed. 16 AGRICULTURE HANDBOOK 3 3 2, U.S. DEPT. OF AGRICULTURE 2. Refill to the marked point in the tank. Single-Nozzle Hand Sprayers Change the number of pints or quarts required to gallons by dividing by 8 or 4 and divide by the 1. Use the same procedure as for hand-type fraction of an acre sprayed. boom sprayers, except measure off an area 10X43.6 (436 square feet) to obtain the basic Example: data for determining sprayer output and calculate Swath width=4 feet as follows: Water required to refill=5.5 pints, or 0.69 436 ^ ^, , gallon —^-—^ = 0.01 acre sprayed =0.030 acre sprayed If 2 pints, or 0.25 gallon, is used, then 4o, OOU 0.25 gallon ^_ „ ^ ^^^ =25 gallons per acre. -^7^ = 23 gallons (approximately) per acre 0.01 acre ^ ^ U.Uo 2. Determine the amount of herbicide for each tankful as follows : 3. If too much spray is applied, walk faster or Capacity of tank=3 gallons use a lower spraying pressure until the desired Output of sprayer=25 gallons per acre volume is achieved. Use the reverse procedure to Desired rate per acre=2 pints obtain more volume. For larger volumes, change 3 Then — =0.12 acre per tankful the orifice size of the nozzle. ^o 4. Determine the amount of herbicide for each 2 pintsX 0.12 acre=0.24 pint per tankful tankful by dividing the capacity of the tank in 0.24 pintX32 tablespoons=7.7 tablespoons, gallons by the number of gallons applied per acre or about 0.5 cup to obtain the fraction of an acre each tankful will spray. Multiply that fraction by the desired rate Aerial Sprayers of application per acre. 1. To determine the rate of flow per acre and per minute, put a measured amount of spray in Example : the tank or fill the tank with water to a definite Capacity of tank =3 gallons level. Instruct the pilot to turn on the spray for a Output per acre=23 gallons timed interval, for example 60 seconds, while flying Rate per acre=2 pints level and straight at the speed to be used for 3 Then — = 0.13 acre per tank spraying. Subtract the velocity of headwind from the airspeed to obtain the groundspeed. When the 2X0.13=0.26 pint per tank plane lands, drain and measure the liquid remain- 1 pint=16 fluid ounces=2 cups=32 table- ing in the tank; or with the plane in the location spoons where the tank was filled, measure the amount Then 0.26X32=8.3 tablespoons, or 0.5 cup, required to refill the tank to the same level. Com- per tank, or 2.8 tablespoons per gallon pute the flow rate in gallons per minute as follows : S= groundspeed of plane per hour (assume 80 m.p.h. airspeed—5 m.p.h. headwind=75 m.p.h.) Ti^= width of effective swath (not total swath) in feet (assume 40 feet) r=time sprayed in seconds (assume 60 seconds, or -^) or 0.017 hour) 60 0= gallons used (assume 12.5) Th n ^ C^^ m.p.h.)X5,280 feet per hourX^T (40 feet)XT (0.017 hour) -6.18 acres 43,560 square feet Gallons per minute=^=—p-= :12.5 12 5 Gallons per acre=7r^ = 2.02 6.18 2. To determine the amount of herbicide re- 2 pints per acre is the desired rate, then quired for each filling of the tank, divide the 120 capacity of the tank by gallons per acre applied —— r=.60 acres sprayed per tank and and multiply by the desired rate per acre. Example : 60X2 pints=120 pints (15 gallons) of If 120 gallons is the capacity of the tank and herbicide required. SUGGESTED GUIDE FOR WEED CONTROL 19 6-9 17 HOW TO DETERMINE OUTPUT OF Ground applications of herbicides seldom should SPREADERS be made during winds of more than 10 to 15 miles per hour. Applications by airplane should stop For acceptable accuracy, calibration of raechani- when winds become stronger than 6 to 8 miles cal broadcasters or spreaders for applying dry per hour. herbicide formulations must be done with the The herbicide 2,4-D and other phenoxy herbi- actual material under the conditions to be en- cides should never be applied when wind of any countered in the field. Where calibration pans velocity is blowing across the area to be sprayed are available for spreaders to catch the material toward nearby valuable sensitive plants. during trial runs and retain it for weighing, calibration is a simple procedure. Determining Humidity and maintaining a desired rate of application by High or moderate humidity increases the hand or mechanical blowers, broadcasters, and effectiveness of most herbicide applications to other devices not equipped for catching the foliage, because it reduces losses of spray from material applied require a more comphcated and evaporation and aids absorption of the chemicals wasteful procedure. by weed foliage. Low humidity, on the other Mechanical Spreaders With Calibration Pans hand, reduces the effectiveness of herbicide sprays by increasing the rate of evaporation. The dis- 1. Fill the spreader at least half full of the advantages of low humidity can be overcome material to be applied. With the calibration pan partially by using oil or oil-water emulsions instead in place, push or pull the spreader by hand or of water as spray diluents. power-driven vehicle over terrain typical of that to be treated for a sufficient distance to cover Temperature 0.01 acre, or 435.6 square feet. For a spreader 3 435.6 Moderate temperatures, ranging from 70° to feet wide, the distance should be —^:= 145.2 85° F., are favorable for spray applications of most herbicides. Low temperatures during the week feet. For a spreader 8 feet wide, the distance before spraying often slow plant growth and retard would be —-^ = 54.45 feet. herbicidal activity. High temperatures increase o losses of herbicides that are volatile and increase 2. Weigh the material from the calibration pan the possibility of injury to crops from selective and multiply by 100 to give the amount applied herbicides. The carbamates, dinitro compounds, per acre. and high-volatile esters of phenoxy compounds 3. Continue this procedure with adjustments of the feed mechanism until the desired rate is volatilize rapidly at temperatures above 80°. At achieved. temperatures above 90°, even the low-volatile esters of 2,4-D and other phenoxy compounds Hand Broadcasting and Mechanical Devices become significantly volatile. In general, do not Not Equipped To Catch Herbicide use herbicidal sprays when the temperature is Begin with a weighed amount of herbicide above 90°. formulation. Apply the material to a measured area, preferably 435.6 square feet, or 0.01 acre. Rainfall Weigh the remaining material and subtract from Rainfall immediately after postemergence foliage the initial weight to determine how much was applied. Continue the procedure with appro- applications of herbicides may reduce thé effective- priate adjustments until the desired rate can be ness of the amine salt formulations of 2,4-D, water- approximated in repeated trials. If the treatment soluble dinitro compounds, and some other foUage period extends over several hours or days, occa- toxicants. Usually effectiveness is not reduced if a sionally check the rate being applied by weighing moderate rain occurs several hours after post- the amount applied to a measured area and make emergence application. The effectiveness of pre- any necessary corrective adjustments. emergence herbicide treatments may be increased by moderate rain occurring shortly after applica- EFFECT OF WEATHER CONDITIONS ON tion. In low-rainfall areas sprinkler irrigation is HERBICIDE APPLICATIONS often used with good results when the water is Wind applied immediately after preemergence herbicide applications. However, if heavy rains occur soon Winds cause improper distribution of herbicides and greatly increase the hazard of damage from after preemergence treatments, control of weeds drift to sensitive crops in nearby fields or gardens. may be reduced or crop damage increased. 18 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE WEED CONTROL IN FIELD CROPS The treatments described for weed control in Local recommendations of State agricultural ex- field crops (tables 2-4) are, in many cases, com- periment stations and extension service weed ponents of a program involving two or more treatments. Because problems and conditions vary specialists, herbicide labels provided by the manu- widely, it would be impractical to attempt to list facturer, and local conditions must be considered the hundreds of différent combined practices that in developing programs that include several would be necessary to cover all localized problems. treatments. TABLE 2.—Weed control infield row crops [Numbers in parentheses=pounds of active ingredient per acre unless otherwise indicated: for herbicide tolerances, see Appendix] Treatment Time of application Weeds controlled Remarks Rotary hoe in and After 2 in. tall but All seedling weeds that Effective only on shallow-rooted between rows. before stalks stiffen. are uprooted. seedling weeds. Shallow cultivation (2 From emergence to lay- All weeds Use often enough to control weeds in. deep or less) by. while young; this practice will between rows. control but seldom eradicates deep- rooted perennial weeds. Flame Before corn is 2 in. tall Kills tops of most weeds If less than 2 in. tall, corn will be and after 12 in. tall. up to 4 in. tall. burned to ground but will recover; if 12 in. tall, is tolerant; if 3-10 in. tall, may be severely injured if flamed; do not repeat flaming of 2-in. stage. Atrazine (2-4) _ In fall preceding year of Quackgrass, many small Incorporate 2-4 in. deep; may persist corn production, in seeded annual weeds. for more than one crop season in spring before planting amounts toxic to sensitive crops. corn, or half in fall plus half in spring. Atrazine (2-4) or After planting but before Most small-seeded Atrazine works effectively with less simazine (2-4). emergence. annual weeds. soil moisture than simazine; simazine controls broadleaf signalgrass better than atrazine; may persist for more than one season in amounts toxic to sensitive crops. CDAA (3.5) plus _do_ _do_ Planting corn deeper than 1 in. will TCBC (7). increase safety margin. TCBC may persist for more than one season in amounts toxic to sensitive crops. CDAA (4) _do_ Most annual grasses, Primarily for use on dark soils high in organic matter; do not use on coarse-textured soils. Propachlor (4). _do_ do More satisfactory on fine-textured soils but can be used on coarse- textured soil. Diuron (0.4-0.8). -do_ Most small-seeded May cause serious injury if corn is annual weeds. planted less than !}{ in. deep. 2,4-D (1-2) -do_ do Planting corn deeper than 1 in. in- creases safety margin; low-volatile esters are preferred formulations in most States; in some States amine formulations cause injury, particu- larly in sandy soils; use only amine or low-volatile esters where such susceptible crops as cotton, grapes, tobacco, or tomatoes are nearby; follow precautions to avoid drift of Atrazine (2-4). any formulation. Before weeds are more Most annual weeds less Apply as foliage spray to corn and than 1 in. tall; do not than 1 in. tall. weeds. apply later than 3 weeks after planting. SUGGESTED GUIDE FOR WEED CONTROL 1969 19 TABLE 2.—Weed control in field row crops—Continued Treatment Time of application Weeds controlled Remarks CORN—continued Atrazine (1). When corn is 20-30 in. _do_ Apply as basally directed spray to tall and weeds not minimize contact with corn; nor- over 1 in. tall. mally add 1 pt. surfactant to each 25 gal. field spray mixture. DNBP (1-2). After corn emergence Most small-seeded an- Apply as foliage spray to weeds and but before 2-leaf nual weeds small corn. stage. enough to be covered by spray. Linuron (1.5) plus 0.5- After corn is 15 in. tall Most annual weeds Direct spray so as to cover only percent surfactant. and weeds are less covered by spray. weeds, soil, and lower 3-6 in. of than 4-6 in. tall. corn. 2,4-D (0.25-0.5) or di- When corn is 4-18 in. Most broadleaf annual Apply as foliage spray to corn and camba (0.25). tall and weeds are weeds; control or weeds until corn is 12 in. tall; smaller than corn. stunting of perennial thereafter use in basally directed broadleaf weeds. spray to avoid spraying into corn whorl; inbred lines of corn may be injured if treated; low-volatile ester or amine formulations less likely to damage nearby susceptible crops; avoid applications when tempera- tures are high and corn is growing rapidly; seed set may be reduced if 2,4-D is applied 2 weeks before silk- ing until after silks are dry; di- camba not registered for use after corn is 36 in. tall; avoid drift of either herbicide from area of application. Nitrogen solution (80- When corn is 20-30 in. Most annual weeds less Apply as basally directed spray con- 120) N plus one of tall. than 1 in. tall; some tacting only weeds, soil, and lower following additives: annual weeds up to 3-4 in. of stalk; need spray equip- Atrazine (1), linuron 3-4 in. tall. ment, such as stainless steel or (0.6), diuron (0.6), fiberglass not corroded by nitrogen ; 2,4-D (0.3) ; add 0.5- agitation required; clean field of percent surfactant to weeds when corn is 12 in. tall. mixture. 2,4-D (0.5) in drill After last cultivation- Most small-seeded an- Apply with drop nozzles of 2 volume row and (1.5) be- nual weeds from after capacities (small nozzles for drill tween rows. last cultivation until row, large nozzles for between harvest. rows) ; direct spray to contact only weeds, soil, and lower 3-4 in. of corn. EPTC (2)_ Immediately before Annual grasses, wild Incorporate 1-2 in. deep; corn planting. cane, some annual planted deeper than 2 in. may be broadleaf weeds. severely injured. Seedbed preparation Before and at planting. Helpful in controlling Locally proper techniques of seedbed and fungicide treat- all weeds. preparation and planting procedures, ment of seed. including use of fungicides, that lead to quick emergence of healthy uniform stands on uniform seedbeds are essential to optimum results from weed-control practices. Hand hoeing and spot Usually when cotton is All weeds resistant to Apply as needed, normally on spot spraying. 6-18 in. tall where other control basis, to remove weeds escaping other control measures measures. other control practices; spot re- are used. moval, by hoeing or chemicals, of resistant weeds may be necessary to prevent their increase over several years. 20 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE TABLE 2.—Weed control infield row crops—Continued Treatment Time of application Weeds controlled Remarks COTTON—continued Cultivate with tools From cotton emergence Generally all weeds More effective if used before weeds such as sweeps set to approximately 18 growing between are more than 2 in. tall; cultivation to cultivate 1-2 in. in. tall. rows. too close to row or too deep may deep. damage cotton; select type of cultivation with regard to other operations that may precede or follow cultivation. Cross-cultivate with From cotton emergence Generally all weeds Used in check-planted or drilled tools such as shield- to approximately 15 growing between rows cotton in lieu of check planting; type sweeps, sweeps, in. tall; cultivate and most weeds in cross-cultivation generally or disk hillers and first in direction of restricted to relatively level fields; sweeps set to planting, then at one of most effective controls for cultivate 1-2 in. right angles to chemical-resistant weeds such as deep; distance direction of planting. Johnsongrass, nutsedge, and between inside tools perennial vines; effectively used determines cotton in combination with other control stand left. measures. Flame in rows and Flame directed into Most small plants Best used on small weeds to keep between rows. row at base of cotton enveloped by flame clean field clean; may be of value plants can be used will be topkilled; in carefully planned salvage after cotton is 10-12 large grass plants programs; greatest hazard arises in. high until it is can be slowly burned from burning vegetation killed so large it is damaged back by series of by previous flaming; this hazard mechanically by light flamings. can be avoided with several light equipment; flame flamings where weed growth is between rows can be heavy; for in-row flaming, direct started any time. burners so as to keep high heat zone in drill row near soil surface; use hooded burners for flaming between rows. Incorporate trifluralin From several weeks to Most grasses from seed; Incorporate immediately after (0.5-1), nitralin immediately before some small-seeded application; mix uniformly 1-2 (0.5-1), or DCPA planting. annual broadleaf in. deep; incorporate after seedbeds (8-10.5) in soil. weeds such as pigweed are formed, or prepare seedbeds and purslane. after incorporation by method that keeps herbicide in position no deeper than 1 in. below point at which cottonseeds are to be planted. Apply EPTC (1-1.5) In conjunction with Johnsongrass from Use in combination with preplanting 1 in. subsurface in planting only. seed, nutsedge, most trifluralin or preemergence diuron; two 6-in.-wide annual weeds. follow with postemergence naphtha, bands centered 7 postemergence DSMA, and possibly in. from drill row. other postemergence treatments ; special instructions for triband weed control are essential to this practice. CIPC (4-10), DCPA After planting but Most small-seeded Normally apply in conjunction with (8), diuron (0.4-1.6), before emergence. annual weeds. planting; usually restrict to band monuron (1.6), treatment; apply CIPC as spray norea (0.75-2.5), or or granules; incorporate granular prometryne (2-2.4). CIPC Y2 in. deep; in general, only use DCPA on very fine soils and monuron on very coarse soils. Naphtha, 20 gal. per 1-3 applications after Most annual weeds in Apply as laterally directed spray to acre of band actually smallest cotton is 2 in. seedling stage; peren- drill area at less than 1 in. above treated (5 gal. per tall and before bark nial grasses and nut- soil; diseased or mechanically 13,068 row-ft. of cracks appear (about sedge will be topkilled damaged cotton may be severely 10-in. band). 1 week after emergence if treated in early injured; naphthas not developed until 4 weeks after emergence stages; few specifically for cotton may not be emergence). perennial broadleaf satisfactory. weeds will be top- killed when small enough to be covered by spray. SUGGESTED GUIDE FOR WEED CONTROL 19 69 21 TABLE 2.—Weed control in field row crops—Continued Treatment Time of application Weeds controlled Remarks COTTON—continued Trifluralin (0.75) _ Before first irrigation Most small-seeded annual For western irrigated Cotton Belt after cotton emergence. weeds and johnson- only; apply to soil between rows grass from seed and incorporate immediately to between rows. depth of 1-2 in.; control of annual groundcherry is temporary. DSMA(3) orMSMA(2) 1-2 applications after Most annual grasses, Apply as basally directed spray; 2 ap- smallest cotton is at seedling cocklebur, plications are frequently necessary least 3 in. tall but few other broadleaf for good control; normally use 1 pt. before first bloom weeds; nutsedge and surfactant for each 25 gal. spray opens. small johnsongrass mixture; DSMA and MSMA appear will be topkilled. more effective during hot, dry periods. MSMA (2) or DSMA 1-2 applications after Most annual weeds ; nut- Apply as basally directed spray; (3) plus norea (0.8). smallest cotton is at sedge and small normally use 1 pt. surfactant for least 3 in. tall but johnsongrass will be each 25 gal. spray mixture; DSMA before first bloom topkilled. or MSMA plus norea is less de- opens. pendent on weather conditions than either herbicide used alone. MSMA (2) or DSMA 1-2 applications after _do_ Apply as basally directed spray ; nor- (3) plus diuron (0.2). smallest cotton is at mally use 1 pt. surfactant for each least 6 in. tall but 25 gal. spray mixture; DSMA or before first bloom MSMA plus diuron is less dependent opens. on weather conditions than either herbicide used alone. MSMA (2) or DSMA 1-2 applications after _do_ Apply as basally directed spray ; nor- (3) plus fluometuron smallest cotton is at mally use 1 pt. surfactant for each (0.8). least 3 in. tall but 25 gal. spray mixture; DSMA or before first bloom MSMA plus fluometuron is less opens. dependent on weather conditions than either herbicide used alone. Diuron (0.2-0.4) _ 1-2 applications after Most annual weeds if Apply as basally directed spray; add cotton is 6 in. tall. treated when less than 1 pt. surfactant for each 25 gal. 3 in. tall, young, and spray mixture; poor control should actively growing. be expected under droughty conditions. For lay-by purposes, Once when cotton is 12 Most small-seeded annual Apply as basally directed spray ; add split application; in. tall; again when weeds germinating 1 pt. surfactant for each 25 gal. diuron (0.3-0.75) per 14-25 in. after treatment; spray mix; normally do not cultivate application. young actively growing after first application ; for this weeds less than 3 in. reason split-application technique is tall. not suggested where resistant weeds are present. For lay-by purposes, When cotton is 15-24 Most small-seeded Apply as basally directed spray; add single application ; in. tall. annual weeds germi- 1 pt. surfactant for each 25 gal. CIPC (8), diuron nating after treatment; spray mix if emerged weeds are (0.5-1.5), linuron young actively grow- present; in irrigated areas, water (0.5-1.5), monuron ing weeds less than management is essential to insure (0.5-1.2), or 3 in. tall if surfactant is thorough wetting of beds after added. application. prometryne (1). Dalapon should be applied to wet all For spot spraying; Before johnsongrass Established and seedling dalapon, 0.74 lb. per flowers for best con- johnsongrass. foliage ; apply TCA ester to wet 5 gal. water, or TCA trol. lower 4-6 in. of all johnsongrass ester, 1 lb. per 5 gal. stems in clump; half rate of TCA ester is adequate on johnsongrass up diesel fuel. to 12 in. tall if applied to wet all leaves ; spot treatments seldom eco- nomical if infestation exceeds 5 percent. 22 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE TABLE 2.—Weed control infield row crops—Continued Treatment Time of application Weeds controlled Remarks PEANUTS Seedbed preparation Before planting and Control of all weeds is Improper land preparation and culti- and cultivation; bury after emergence. affected by seedbed vation often increase incidence of litter at least 3 in. preparation; cultiva- southern blight, which may dras- deep with moldboard tion between rows tically reduce peanut yields and plow in preparing flat controls all weeds. quality; broken stands intensify seedbed; shallow- weed problems; rough seedbeds com- running, nondirting, plicate use of herbicides. flat sweeps are most satisfactory for cul- tivation. Vernolate (2-2.5) From 2 weeks to imme- Most annual weeds; Incorporate about 3 in. deep; usually diately before plant- suppresses nutsedge. temporary stunting and leaf fusion ing. of peanuts ; do not use seed of poor vitality. Benenn (1.1-1.5) From 2-3 weeks to Most grasses from seeds; Incorporate 2-3 in. deep immediately immediately before many annual broadleaf after application. planting. weeds. Benefin (0.7-1.1) plus do Most annual weeds; Incorporate 2-3 in. deep immediately vernolate (1.5-2). suppresses nutsedge. after application ; satisfactory late- season control of grasses. Sesone (2.7), 2,4-DEP After planting but before Most small-seeded All these herbicides may cause injury, (3), NPA (2-4), or emergence. annual weeds. especially in cold, rainy periods DNBP (9-12). during crop emergence; crop injury usually temporary; do not use seed of poor vitality. DNBP (6) alone or When peanuts are crack- -do_ Mixtures usually perform better than DNBP (1.5) plus one ing soil unless weeds single herbicides; timing is critical; of following additives : become visible first; in emergent sprays are most effective if 2,4-DEP (2), sesone this case apply herbi- applied when weeds are first visible; (2-2.7), diphenamid cides before peanuts treatment after oldest peanuts have (2-3), or NPA (3). start to crack soil. more than 2 leaves is very hazardous ; peanuts from seed of poor vitality are likely to be severely injured. Postemergence DNBP Before peanuts are more .do_ Less effective than emergent mixtures ; (3). than 13^-2 in. in diam- peanut foliage will be injured, especi- eter (3- to 5-leaf ally in hot weather or hot, wet stage). weather. Postemergence DNBP Within 1 month after .do_ Can be used if needed as f oUowup treat- (1.5). peanuts first crack soil ; ment after emergent mixtures ; apply use 1-2 applications. when weeds first become visible; pro- tect peanuts from spray with shields or similar devices. SAFFLOWER EPTC (3) Several weeks to imme- Winter annual weeds in- Incorporate in top inch of soil imme- diately before planting. eluding volunteer diately after application. cereals. IPC (2-3) do Barley, wild oats Do. Barban (0.38) When wild oats have 1-2 Wild oats Apply as broadcast spray. true leaves (approxi- mately 4 in. high). SORGHUM Cultivation. Before planting to destroy All weeds. Preplanting cultivation should gener- several weed crops and ally be shallow to reduce moisture after crop emergence loss; postemergence cultivation until lay-by. should be often enough to control weeds in young stages of growth ; set row widths to facilitate cultivation. SUGGESTED GUIDE FOR WEED CONTROL 1969 23 TABLE 2.—Weed control in field row crops—Continued Treatment Time of application Weeds controlled Remarks SORGHUM—continued Rotary hoe in and be- After sorghum is 2 in. All seedling weeds young Effective only on shallow-rooted seed- tween rows. tall until stalk begins to enough to be uprooted. ling weeds. stiffen. Atrazine (1-2) After planting but be- Most small-seeded an- Some injury to sorghum may occur; fore crop emergence. nual weeds. plant sorghum 1 in. deep or deeper to increase safety margin; do not use atrazine on sorghum grown in coarse- textured soil or soils low in organic matter. Norea (1.6-2.4), norea do Norea alone kills most Plant sorghum 1 in. deep or deeper to (1.6-2) plus propazine annual grasses; increase safety margin. (0.8-1), or atrazine mixtures increase con- (0.8-1). trol of annual broad- leaf weeds. Propachlor (4-5) do Most small-seeded Do. annual grasses, some broadleaf weeds. Propazine (1.5-4) do Most small-seeded Do. annual broadleaf weeds, some annual grasses. Atrazine (2-3) After crop emergence Most annual weeds less Apply as broadcast spray in sorghum; than 1 in. tall. or if necessary to cover weeds, use directed basal spray. 2,4-D (0.25-0.5) When crop is 4-12 in. Most broadleaf annual Apply as foliage spray to crop and tall. weeds. weeds while sorghum is 4-12 in. tall; basally directed spray in sorghum 6-12 in. tall presents less danger to crop and may be used if weeds are shorter than crop; some injury to sorghum by 2,4-D may occur re- gardless of growth stage at appli- cation. Flame _ After sorghum is 12 in. Kills tops of most small Direct flame basally; balance speed tall. weeds. and pressure to kill tops of small weeds without causing more than slight damage to lower leaves of sorghum; flame few rows day before ñeld is to be flamed; adjust equipment according to appearance of trial rows 1 day after flaming. SOYBEANS 6-10 cultivations to 6-8 weeks before plant- Perennial grasses such as Alternating disk with field cultivator depths of 2-4 in. ing. Johnsongrass and is as effective and more economical quackgrass, most than using 1 implement; cultivate annual weeds. twice in 1 day if wet weather delays schedule; most effective in dry weather; may reduce soil moisture to critical levels, making it advisable to wait for rain before planting. 2-3 shallow cultivations 2-4 weeks before plant- Most annual weeds; Less likely to reduce soil moisture to at depths no greater ing. some control of per- critical levels than intensive cul- than 2 in. ennial grasses such as tivations at greater depths; use only Johnsongrass and where weeds have emerged or are nutsedge. emerging. Cultivate in and be- From unifoliate stage of Most shallow-rooted Best results obtained when soil is loose tween rows with beans until first tri- annual weeds in or lightly crusted; safety to soybeans rotary hoe at high foliate leaf has fully emerging stage. increases if rotary hoeing is done speed. expanded. only when beans have lost some turgidity; chance of yield reductions increases markedly if soybeans are rotary hoed after full expansion of first trifoliate. 24 AGRICULTURE HANDBOOK 33 2, U.S. DEPT. OF AGRICULTURE TABLE 2.—Weed control infield row crops—Continued Treatment Time of application Weeds controlled Remarks SOYBEANS—continued Cultivate between rows As needed after emer- All weeds. Cultivation is effective and usually with tools such as gence and until beans most economical method of con- sweeps. become too large. trolling weeds growing between rows. Dalapon (3.7-7.4) ; use In spring when johnson- Johnsongrass- Disk treated fields 4-7 days after 0.5-percent surfactant grass is approximately treatment; plant soybeans no sooner in spray. 1 ft. high (at least 4 than 3 weeks after disking; fall weeks before planting plowing delays emergence of johnson- soybeans). grass in northern areas; spring plow- ing after dalapon treatment is advis- able so soybeans can be planted earlier; use trifluralin or nitralin incorporated in soil before planting or amiben preemergence to control seedling Johnsongrass not affected by dalapon treatment. Amiben (2-3), linuron After planting but before Most small-seeded an- Preemergence herbicides likely to cause (1-3), CDAA (4-5), emergence. nual grasses, some injury on very coarse-textured soils; NPA (3-4), or NPA broadleaf weeds. soybeans may be injured severely by (3) plus CIPC (2- linuron on soils low in organic 2.7). matter. Nitralin (0.5-1.1), tri- From several weeks to Most annual grasses, Incorporate herbicides 1-2 in. deep in fluralin (0.5-1), or immediately before some broadleaf weeds; soil; these preplanting treatments vernolate (2-3). planting. some control of nut- may cause injury on very coarse- sedge with vernolate. textured soils; nitralin (1.1) fre- quently fails to control weeds adequately on dark high-organic soils of North Central States. DNBP (1.5) plus NPA After planting but before Most small-seeded an- For sandy soils of Coastal Plain, (2-3). crop emergence. nual grasses, some application 2-3 days after planting broadleaf weeds. reduces chances of crop injury. Nonfortified naphthas 1 application when beans Most small-seeded an- Apply as laterally directed spray to (same as for cotton) are 12-19 days old; if nual weeds in seedling 10-in. band centered over row at at approximately 20 needed, second appli- stage; kills tops of less than 1 in. above soil (5 gal. per gal. per acre of land cation may be made most small perennial 13,068 row-ft.) ; do not treat beans actually treated. no sooner than 5 days weeds. more than 4 weeks old. after first application. 2,4-DB (0.2). 1 application 2 weeks Cocklebur Apply as broadcast foliage spray; before early bloom normally use amine formulation; until midbloom when treatment often injures soybeans cocklebur plants are but symptoms (stem curvature and growing above soy- drooping leaves) generally disappear beans. within 1 week after treatment; in- jury is more severe if treatment is made when soil is very dry; timing and rate very critical. Chloroxuron (1-1.5) Postemergence when soy- Most actively growing Apply as broadcast foliage spray or as beans are over 4 in. annual broadleaf laterally directed spray at base of tall and weeds are less weeds less than 2 in. soybean plants; use 0.3-0.5 percent than 2 in. tall. tall; very little control surfactant in spray; agitate spray of annual grasses. mixture; treatment often injures soybeans, but stunting and leaf necrosis usually disappear within 2-3 weeks; injury usually does not reduce soybean yield. SUGGESTED GUIDE FOR WEED CONTROL 19 69 25 TABLE 2.—Weed control infield rom crops—Continued Treatment Time of application Weeds controlled Remarks SOYBEANS—continued 2,4-D wax bars C6 bars After most sesbania Sesbania. Wax bars are suspended from booms for 4 rows). plants have grown or rod attached to rear of tractor so above soybeans. as to travel 2-3 in. above soybean plants; sesbania stems rub 2,4-D wax formulation off bars; speed should not exceed 4 m.p.h. and should be slower in extremely heavy infestations ; handle wax bars care- fully and remove from tractor when not in actual weed-control operation; apply no more than 0.5 lb. per acre of 2,4-D. SUGAR BEETS Cultivation Postemergence (variable) _ Small weeds in rows, all Weeds between rows easily controlled weeds between rows. by cultivation ; mechanical thinners provide some weed control in rows; various devices such as harrows with flexible tines used successfully for weed control in row if beets big enough to withstand operation and weeds small enough to be killed. Incorporate preplanting Immediately before Wild oats_ diallate (1.5-2) in planting. soil. IPC (3-5) do Wild oats, volunteer Incorporate in soil right after applica- cereals, some other tion; does not control foxtail. annual grasses. Pebulate (4-5), cycloate do- Most annual grasses, Incorporate in soil immediately after (3-4),orEPTC (1-2.5). many annual broad- application; margin of safety for leaf weeds. EPTC is narrow; use no higher rate than local experience has shown to be safe. Pyrazon (4-4.8)-_--- do_ Many annual broadleaf Incorporate in soil immediately after weeds. application; crop injury may occur on coarse-textured soils in Pacific Northwest. Preemergence endothall After planting but be- Many annual weeds _ (5.5). fore crop emergence. Preemergence pyrazon do Many annual broadleaf (3-4). weeds. Preemergence TCA do Most annual grasses (5-7). except wild oats and volunteer cereals. Postemergence barban When wild oats in 2-leaf Wild oats '- Apply as broadcast foliage spray. (0.6-0.75). stage. Postemergence dalapon When crop has emerged Most small grassy weeds. Do. (2-3). until it has 4 true leaves and grassy weeds are less than 3 in. tall. Postemergence endothall When crop has emerged Smartweed, wild buck- Use lower rate when beets have less (0.75-1.46). until it has 6 true wheat, some other than 2 true leaves; when tempera- leaves and weeds are broadleaf weeds. ture is above 80° F., endothall may less than 23^ in. tall. cause excessive injury, especially to very small sugar beets. Postemergence pyrazon When crop has emerged Many annual broadleaf (4). but before weeds have weeds. more than 2 true leaves. Pyrazon (4) plus Apply when first 2 true Most annual grasses, Apply only as band foliage spray; dalapon (2). leaves of crop are pea many annual broadleaf adequate soil moisture should be size. weeds. available for good weed control; do not use if pyrazon was applied before planting. 26 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE TABLE 2.—Weed control infield row crops—Continued Treatment Time of application Weeds controlled Remarks SUGARCANE Fallow plowing. 6-8 fallow plowings Johnsongrass from seed during spring and and rhizomes. summer before sugar- cane is replanted. Atrazine (2-4), simazine Immediately after plant- Most annual grasses, Apply re-treatments as basally (2-4),diuron(2-3),or ing or ratooning; most many small-seeded directed sprays. monuron (2-4) ; for may be repeated and/ annual broadleaf organic soils of or supplemented with weeds. Florida: CD A A (8) other herbicides plus 2,4-D (2) ; for during growing season. Hawaii only: Ametryne (4-8). Fenac (4-6) ; for Fenac in fall after plant- Johnsongrass from seed, Apply fenac (6-8) broadcast in Florida; Louisiana only: ing in Florida; in most annual grasses, apply fenac or terbacil on 24- to Terbacil (3.2). Louisiana apply fenac many broadleaf weeds. 30-in. band in Louisiana. and terbacil in fall after planting and in early spring (split application) or spring only. For Florida primarily: Young succulent weeds Most annual grasses, Apply as basally directed spray, Atrazine (2-4) ; for at any time after crop some small-seeded usually as supplement to pre- Hawaii only: Diuron emergence and before broadleaf weeds; in emergence treatment; apply atrazine (2-3.2) plus sur- cane closes in; 1-3 Hawaii many when seedling weeds are approxi- factant, PCP (5) applications may be perehnial grasses and mately IH in. tall. emulsified in naphtha, necessary. broadleaf weeds. or ametryne (2-4). 2,4-D (2) ; for Postemergence when 2,4-D controls chick- Apply as broadcast foliage spray. resistant weeds: needed to vigorously weed, henbit, morning- 2,4,5-T or silvex (1). growing weeds. glory, pigweed; other chemicals control these weeds plus dogfennel, ground- cherry, koa haole, nightshade, wild lettuce. TOBACCO Commercial urea (1) Urea-cyanamide or All annual weeds in For plant beds only ; thoroughly plus calcium cyanamide in October plant beds. mix urea-cyanamide or calcium cyanamide (0.5) in mid-Atlantic States. cyanamide with upper 3 in. per sq. yd., or of soil by disking or raking; methyl bromide (1) apply methyl bromide to well- per 100 sq. ft. pulverized seedbed under gasproof cover; methyl bromide is very poisonous; many users employ specially trained personnel to apply it. Diphenamid (4-6). Immediately after Most annual grasses, Shallow incorporation before planting seeded some small-seeded transplanting may improve tobacco or after broadleaf weeds. effectiveness. transplanting and before any weed emergence. Pebulate (3). Shortly before trans- Suppresses nutsedge, Incorporate 2-3 in. deep with power- planting. controls many annual driven rotary hoe; read label weeds. carefully for area and other restrictions. Benefin (1.2-1.5). After beds are formed Many annual grasses, Incorporate 2-3 in. deep with but before tobacco some broadleaf weeds. power-driven rotary hoe. is set. SUGGESTED GUIDE FOR WEED CONTROL 19 69 27 TABLE S.-—]Veed control in close-drilledßeld crops [Numbers in parentheses=pounds of active ingredient per acre unless otherwise indicated; for herbicide tolerances, see Appendix] Treatment Time of application Weeds controlled Remarks ESTABLISHED ALFALFA Flaming- Twice at 3-day interval Dodder seedlings, Spot flaming can be used also for in stubble after dodder attached to isolated patches of dodder in seed harvest. stubble. crop. Drying of soil in irri- Whenever feasible during Dodder seedlings gated areas by in- growing and harvesting creasing interval season. between irrigations. Shading by crop _do_ Alfalfa, through shading after it is 2 ft. tall, provides important part of full- season control of dodder if dodder is controlled by other methods while alfalfa is less than 2 ft. tall. Frequent, shallow In early spring and -do- cultivation. in stubble after harvest. CIPC (6) (granular To moist soil before Dodder seedlings, some Supplement with cultural practices formulation) or dodder attaches to annual weeds; DCPA described previously to obtain full- DCPA (10). host in spring. provides some control season control; use DCPA only on of attached dodder. seed crops. Dichlobenil (2) (granu- Shortly before or after Dodder seedlings, most Supplement with cultural practices lar formulation). irrigation and before annual weeds, some described previously to obtain full- dodder attaches to perennials. season control; use only on seed host. crops; may be applied twice during season. Diuron (1.5-3.2); In fall or winter when Manv annual weeds- Apply before germination of weeds or simazine (0.8-1.6). alfalfa is dormant or while still seedlings; remove or semidormant. burn crop residue before treating; simazine registered for use only on at least 1-year-old alfalfa in Pacific Northwest only. DNBP (1.3-2.2) After first hay crop is Annual broadleaf weeds _. Do not graze treated areas or feed plus 20-50 gal. removed but before treated forage to livestock. diesel or weed oil regrowth starts. plus 50-100 gal. water. EPTC (2-4) Immediately before Annual grasses, many Incorporate in soil by disking or planting. broadleaf weeds. rotary tiUing; EPTC volatile, lost if applied to wet soil or left on soil surface more than 3^ hour. 2,4-DB (1-2) _ Postemergence when Broadleaf weeds Alfalfa susceptibility increases with weeds are less than age. 3 in. tall. DNBP (amine salts) Postemergence when Some broadleaf weeds- (0.75-1.5). weeds are small and alfalfa has 2 or more true leaves. Dalapon (2-2.2). Postemergence when Grass seedlings- Stunts alfalfa temporarily; may be grasses are less than 3 repeated later in season; do not feed in. tall. first year's growth to dairy cows or animals being finished for slaughter. EPTC (2-3); EPTC immediately Seedlings of grass and Use this treatment for spring seeding 2,4-DB (1-2). before planting; broadleaf weeds. and seed harvested during seeding 2,4-DB postemergence year. if broadleaf weeds occur. (Immediately before Dodder, many annual Incorporate lightly if rainfall not ex- planting. grass and broadleaf pected or furrow irrigation cannot DCPA (10). weeds. follow soon after application. Or immediately after do Sprinkle-irrigate soon after application. planting. CIPC (5) (granular After alfalfa has first Dodder, some annual Apply granules to moist soil; stunting formulation). pair true leaves. weeds. of alfalfa probable; earlier applica- tion may cause severe injury; must be applied before dodder attaches to host; must plant alfalfa early so it reaches safe stage before dodder emergence. 28 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE TABLE 3.^—Weed control in close-drilled field crops—Continued Treatment Time of application Weeds controlled Remarks ESTABLISHED GRASSES GROWN FOR SEED Plant in rows and Summer annuals. Not satisfactory where heavy winter cultivate between rains occur and winter annuals are rows. primary weeds. Dicamba (2-3) in Soon after first post- Downy brome Remove all crop residue by burning eastern Oregon; harvest irrigation. or mechanical means immediately^ prometryne (2-3.2) in after harvest; prometryne registered eastern Oregon and for use only on perennial bluegrass eastern Washington; seed fields. IPC (4) in eastern Washington. 2,4-D, 2,4,5-T, MCPA, After seedling crop Most broadleaf weeds. Easier to control small, actively or silvex (0.5-0.75) grasses have 3-5 growing, young weeds than large, or dicamba (0.25- leaves; established slowly growing, old weeds; use 0.5). crop grasses not higher rates only on well-established treated after boot stands. stage but can be re-treated after harvest. ESTABLISHED LEGUMES ^ GROWN FOR SEED Mechanical tillage When weeds are seed- Many annual weeds _ Species present will determine when (shallow) or flaming lings before seeding tillage can be practiced. fields with field weed crop, between hay burners. and seed crops, and in dormant stages. 2,4-DB (0.5-2) Any time during grow- Many annual and peren- Treat weeds when less than 3 in. tall, ing season before bud- nial broadleaf weeds or preferably when less than 1 in. ding of legumes. that are not legumes tall, and growing actively ; use and that are not re- higher rates only for established sistant to 2,4-D. legumes ; not registered for use on lespedeza; may reduce seed produc- tion of clovers and trefoil when applied in spring. DNBP (1.9-2.5) or Preharvest- Desiccation of all weeds Treatment before legume seeds are PCP (4-6) in 5-10 before harvest. mature may reduce their yield and gal. diesel oil, or quality; legumes as well as endothall (0.5-0.65) in weeds are desiccated by treatment; 5-10 gal. water, or DNBP not registered for use on diquat (0.5-0.75) in lespedeza; diquat not registered for 20-40 gal. water. use on lespedeza or birdsfoot trefoil; do not graze fields or feed treated forage to livestock. ESTABLISHED LEGUMES ^ GROWN FOR SEED IPC (3-4) or CIPC In winter when legumes Winter annual Apply before germination of weeds or (3-4). are dormant or semi- chickweed. while still seedlings ; burn or remove dormant. crop residue before treating; use only after legumes have several true leaves. See footnotes at end of table. SUGGESTED GUIDE FOR WEED CONTROL 19 6'9 29 TABLE 3.—Weed control in close-drilled field crops—Continued Treatment Time of application Weeds controlled Remarks ESTABLISHED GRASSES ^ GROWN FOR SEED Atrazine (1-1.2), CIPC Preemergence to weeds Winter annuals, except Treatments listed may be unsatisfac- (2-3), diuron (1-3.2), in fall or while weeds CIPC and IPC will tory in area other than Washington IPC (2-4), or sima- are very small. not control many or Oregon; remove or burn all crop zine (1-2). broadleaf winter residue before treating; CIPC or annuals. IPC may reduce seed yields of grasses if applied after Nov. 1 ; bluegrass and other grasses may be severely injured by atrazine or sima- zine in areas outside Washington and Oregon; atrazine registered for use only on perennial ryegrass; di- uron not registered for use on creep- ing red fescue; IPC not registered for use on orchardgrass, bluegrass, tall fescue; simazine not registered for use on bluegrass. ESTABLISHED TREFOIL GROWN FOR SEED Diuron ( 1.6) In winter when trefoil Manv annual weeds. Apply before germination of weeds is dormant or semi- or while seedlings; burn or remove dormant. crop residue before treating. Select fields relatively Late summer, early fall-__ Perennials, annuals _ Late-summer or fall tillage may not free of weeds; tillage be desirable in some areas where of land in late sum- wind may seriously erode soil. mer and early fall is helpful. Spring tillage Before planting Wild oats_ Spring tillage delays sowing of flax; practice is successful in some areas but may be detrimental to flax yields; use early varieties where sowing is delayed. Diallate (1.5-2) In fall or spring pre- _do_ Incorporate herbicide in soil. ceding spring seeding. Barban (0.3-0.37) When wild oats in 2- _ do Apply as broadcast foliage spray. leaf stage. MCPA (amine or so- When flax is 2-6 in. tall Many broadleaf weeds Apply as broadcast foliage spray; dium salts) (0.1-0.6) and weeds are small, higher rates than those listed re- or 2,4-D (amine salt) quired only in Southwestern United (0.1-0.25). States; MCPA less likely to injure flax than 2,4-D ; do not apply MCPA or 2,4-D after flax reaches early bud stage; varieties differ in tolerance to herbicides. TCA(5),dalapon(0.75), do_ Most annual grasses. Apply as broadcast foliage spray; either one in mix- mixture controls both grasses and ture with MCPA broadleaf weeds. (0.25). See footnotes at end of table. 30 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 3.—Weed control in close-drilledßeld crops—Continued Treatment Time of application Weeds controlled Remarks RICE Use of weed-free crop At planting- Barnyardgrass, beak- Use weed-free rice seed to prevent or seed. rush, mexicanweed, hold down infestations of listed northern joint vetch weeds. (curly indigo), red rice, hemp sesbania (coff eebean). Rotate with row crops Many grasses, broad- Reduces infestations of listed weeds; such as soybeans, leaf weeds, sedges, in some cases can help eradicate cotton, grain sor- aquatic weeds. some weeds. ghums, safflower. Rotate with pasture Reduces infestations of Does not reduce grass infestations. aquatic weeds, broad- leaf weeds, sedges. Phosphate fertilization In previous seeding cr Barnyardgrass and most Reduces competition of listed weeds of other crops pre- just before first annual grasses in dry with rice ; phosphate applied in ceding rice or of rice flooding. seeded rice. standing water stimulates aquatic just before it is weeds; may be applied preplant to flooded for ñrst time. water-seeded rice without stimulat- ing barnyardgrass but may increase problems with aquatic weeds. Rotate with other Many annual weeds, Reduces infestations of listed weeds; small grains com- perennials such as in some cases can help eradicate bined with summer bulrush, cattail, knot- some weeds. fallow after harvest grass, perennial spike- of other small grains. rush. Thorough seedbed Late summer, fall, and Deep-rooted perennials, Reduces infestations but does not preparation of ade- early spring before aquatic weeds, most eradicate listed weeds. quately dried land to planting. annual weeds. kill all weed growth before seeding and repeated shallow cultivations at 1- to 3-week intervals in spring before planting. Water management at From several days before Barnyardgrass, north- White barnyardgrass not controlled seeding. planting to 4 weeks ern joint vetch (curly unless water is held 6-8 in. deep after seeding rice. indigo), hemp sesbania for 3-4 weeks; water seeding en- (coifeebean), signal- courages some aquatic weeds such grass, sprangletop. as algae, annual flatsedge, annual spikerush, ducksalad; therefore dry seeding rice by drilling or broad- casting helps control these aquatic weeds. Flood rice to depth of Flood when grass weeds Barnyardgrass, most Timely and complete draining of 4-8 in. just after rice have 1-3 leaves and annual grasses. water helps control many aquatic and grassy weeds hold for 1-3 weeks. weeds including algae and duck- emerge. salad. Timing of nitrogen Variable Barnyardgrass, other In absence of effective cultural or application to rice. annual grasses, chemical control of listed weeds, aquatic weeds. delay nitrogen application until weeds are flowering to reduce com- petition with rice (this period of flowering usually occurs 50-60 days after seeding rice). Molinate (3) (granular Immediately before Barnyardgrass in water- Incorporate 3-4 in. deep immediately or emulsifiable flooding and seeding. seeded rice. after application; cross-disking or formulation). cross-harrowing with implements going 4-6 in. deep has been satis- factory; safe only on water-seeded rice. SUGGESTED GUIDE FOR WEED CONTROL 1960 31 TABLE 3.—Weed control in close-drüled field crops—Continued Treatment Time of application Weeds controlled Remarks RICE—continued Molinate (3) (granular Postemergence after Barnyardgrass, spike- Flood rice before application and formulation). flooding but before rush, yerba-de-tago. broadcast aerially; maintain flood weeds are 3 in. tall. at least 7 days; gives residual control for 14 days if drained at 7 days; poor weed control on levees and unflooded areas; safe only on dry-seeded rice. MCPA, silvex, 2,4-D, When longest inter- Arrowhead, burhead, Severe injury may occur if rice or 2,4,5-T (0.5-1.5); nodes are }i-% in. ducksalad, ñmbristy- is treated in early-tillering, late- amine salt or low- lis, flatsedge, goose- jointing, booting, or early-heading volatile ester formu- weed, mexicanweed, stages; for emergency treatments lations. northern jointvetch in early stages of rice growth, (curly indigo), red- 2,4,5-T, MCPA, and silvex will stem, hemp sesbania cause less injury than 2,4-D; rapidly (coffeebean), smart- growing weeds are easier to kill than weed, spikerush, water- slow growing weeds; therefore soil hyacinth, water- moisture should be adequate to hyssop, waterplantain, promote rapid weed growth; water waterprimrose. levels should be lowered if necessary to expose weed foliage to sprays; mixtures may be better than single herbicides where several species are present; for example, 2,4-D (0.5) plus 2,4,5-T (0.5) is more effective than either one at 1 lb. where both ducksalad and northern jointvetch (curly indigo) are present; treat only when temperature is 70°-90° F. ; do not mix these herbicides with other pesticides or any material other than water; nitrogen applied to rice before treatment may in- crease its susceptibility; nitrogen applied 7-21 days before treatment has increased susceptibility more than nitrogen applied 1-6 days before herbicide application; nitrogen applied at midseason within 10 days after herbicide may reduce rice injury; rain 1-6 hours after spraying may reduce effectiveness. Propanil (4.5-6)- When grassy weeds are Barnyardgrass, other Do not alter water depth immediately through water and annual grasses, broad- before or after spraying; if before oldest grass is 6-8 in. leaf weeds, sedges. spraying, deep flood is lost by levee above water (42-50 failure, reflood rice to shallow depth days after seeding). (2-3 in.) ; treat when grass has resumed rapid growth and is 5-6 in. tall (similar to shallow-water culture) ; spray droplets of 200-400 micron diameter are preferable to coarser or finer sprays; do not mix propanil with other pesticides; insecticides such as carbaryl, parathion, and methyl parathion may cause injurious interactions if used within 15 days before or after propanil application. 32 AGRICULTURE HANDBOOK. 3 32, U.S. DEPT. OF AGRICULTURE TABLE 3.—Weed control in close-drilled field crops—Continued Treatment Time of application Weeds controlled Remarks RICE—continued Propanil (4-4.5)- Usually 35-45 days after Barnyardgrass, other Spray droplets of 200-400 micron seeding when oldest annual grasses, broad- diameter are preferable to finer or grass is 5-6 in. above leaf weeds. coarser droplets; if grasses are not water and broadleaf prevalent weeds, water may be weeds and sedges are lowered but not drained to expose just above water. foliage of nongrassy weeds ; in such case water level may be raised after spraying as rice develops and temperature increases; do not mix propanil with other pesticides; insecticides such as carbaryl, parathion, and methyl parathion may cause injurious interactions if used within 15 days before or after propanil application. Propanil (3-5) in 10-15 Soon after crop and Annual flatsedge, annual May be used in drill-, broadcast-, gal. water for aerial weed emergence when spikerush, barnyard- or water-seeded rice; if rice is water spraying or in 15-25 grass weeds have 1-3 grass, fimbristylis, seeded, drain or lower water to gal. water for ground leaves and broadleaf gooseweed, hemp expose weed foliage; control is spraying. weeds or sedges are sesbania (coifeebean), improved by flushing field 2-3 days 1-5 in. tall. northern jointvetch before spraying if soil is dry; (curly indigo), signal- postpone spraying for warmer grass, many other temperatures if below 50° F. at annual weeds. night and below 70° during day; flooding may begin 24 hours after application and should be completed in 2-4 days; spray droplets of 200-400 micron diameter are preferable to finer or coarser spray ; do not mix herbicides with other pesticides; insecticides such as carbaryl, parathion, and methyl parathion applied within 15 days before or after propanil have severely injured rice. Propanil (5-6) plus When barnyardgrass is Barnyardgrass. Most effective on rapidly growing surfactant in 12-15 in tillering to jointing grass; if grass is growing slowly, gal. water; use 0.5- stage. light application of nitrogen in percent surfactant in flood 4-7 days before applying spray. herbicide stimulates grass growth ; surfactants not developed specifi- cally for rice may not be satisfac- tory; see propanil (3-5) for droplet size instructions and precautions on temperatures and mixing with other pesticides. Propanil (5). 3-lb. split application to Sprangletop. Apply aerially to water-seeded rice sprangletop less than after draining; cross-apply first 3 in. tall followed bv treatment using 10 gal. per acre 2 lb. 7 days later. total spray; apply second treatment conventionally; begin flushing 1 day after first treatment; see propanil (3-5) for droplet size instructions and precautions on temperatures and mixing with other pesticides. Propanil (3) in 10 gal. When weeds are less Ducksalad, flatsedge, Apply aerially after draining ricefield; water. than 1 in. redstem, spikerush, see propanil (3-5) for droplet size waterhyssop. instructions and precautions on tem- peratures and mixing with other pesticides. SUGGESTED GUIDE FOR WEED CONTROL 196i9 33 TABLE 3.^—Weed control in close-drilled field crops—Continued Treatment Time of application Weeds controlled Remarks RICE—continued Propanil (4-6) plus When weeds are less Ducksalad, flatsedge, Apply aerially after draining ricefield; surfactant in 10 gal. than 6 in. gooseweed, redstem, surfactants not developed specifi- water; use 0.5- spikerush, water- cally for rice may not be satisfac- percent surfactant in hyssop. tory; see propanil (3-5) for droplet spray. size instructions and precautions on temperatures and mixing with other pesticides. Propanü (2-3) in 10 At midseason to weeds Hemp sesbania (coffee- Apply aerially to flooded or drained gal. water. less than 5 ft. bean) . ricefields; see propanil (3-5) for droplet size instructions and pre- cautions on temperatures and mixing with other pesticides. Diuron (0.8-1.2) Before Apr. 10 while Many annual weeds. Registered for use in eastern Oregon, weeds are less than 4 Washington, and Idaho where in. tall. annual precipitation is more than 16 in. Diuron (1.2-1.6) Immediately after .do_ Registered for use in western Oregon planting. and western Washington. Diallate (1-1.25). Preemergence before Wild oats Incorporate in soil. crop sprouts are H in. long. BARLEY, OATS, AND WHEAT 2,4-D (0.25-1) After cereals are well Many annual broadleaf Wheat most tolerant of these crops tillered but before weeds; topkills to 2,4-D; oats least tolerant; pre- boot stage; wheat may several perennial harvest spraying of wheat may be treated shortly weeds. help to dry weeds before harvest before harvest. but earlier treatment is more desirable. MCPA (0.2-0.5) 2-leaf to boot stage _do_ Oats more tolerant to MCPA than to 2,4-D; treatment may be used to control early germinating weeds when cereals are small. Bromoxynil (0.37-0.5). When weeds are small; Many annual broadleaf Not registered for use on oats; when wheat or barley weeds including some effective only on small weeds. is in 2-leaf to boot not adequately con- stage. trolled with 2,4-D or MCPA. BARLEY AND WHEAT UNDERSOWN WITH LEGUMES Postemergence 2,4-D After cereals are well Mustard, yellow rocket, Use only if weed infestation is serious or MCPA (0.12-0.25). tillered (usually 4-8 other broadleaf weeds. enough to result in reduction or in. tall) but before loss of legume stands and reduced boot stage. cereal yield; cereal canopy may help protect legumes from herbicides; waiting later than early joint stage is inadvisable; use lowest gallonage and pressure possible to reduce penetration of cereal and weed canopy; these rates are frequently inadequate for Southern, North- western, and Western United States; check with local authorities for clearances and safety of higher rates. 34 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE TABLE 3.—Weed control in close-drüled field crops—Continued Treatment Time of application Weeds controlled Remarks DURUM WHEAT AND HARD RED SPRING WHEAT Triallate (1) In fall before spring Wild oats Incorporate in soil. planting. Barban (0.25-0.37) When wild oats in 2-leaf do stage but not after crop reaches 4-leaf stage. FALL-SEEDED BARLEY, OATS, AND WHEAT Dicamba (0.25) Postemergence in spring Corn cockle, cow cockle, Mixtures of 0.12 lb. each of dicamba before joint stage. dogfennel, smartweed, and 2,4-D per acre will control wild buckwheat, most mustards better than dicamba alone. weeds susceptible to 2,4-D. SPRING-SEEDED OATS AND WHEAT Dicamba (0.12) for oats Postemergence during Corn cockle, cow cockle, Mixtures of 0.12 lb. each of dicamba and (0.12-0.25) for 2- to 5-leaf stage of dogfennel, smartweed, and 2,4-D per acre will control wheat. crop. wild buckwheat, most mustards better than dicamba alone. weeds susceptible to 2,4-D. 1 Includes alfalfa, birdsfoot trefoil, alsike, ladino, red, 3 Includes bentgrass, bluegrass, creeping red fescue, and white clover, and lespedeza. orchardgrass, perennial ryegrass, and tall fescue. 2 Includes alfalfa, birdsfoot trefoil, and crimson, ladino, red, subterranean, and white clover. TABLE 4.—Control oj perennial weeds in cropland in fallow periods or by spot treatment [Numbers in parentheses=pounds of active ingredient per acre unless otherwise indicated] Treatment Time of application Weeds controlled Remarks ALL KINDS Methyl bromide fumi- Any time during spring, All weeds, weed seed, Apply under gasproof cover after gation, 1 lb. per 100 summer, or fall. rootstocks. sq. ft. thorough tillage of soil; methyl bromide is very dangerous to man and warmblooded animals; most users employ personnel specially trained in its use; for control in small, specialized areas ; soil tempera- ture should be above 65° F. for effective results. Intensive cultivation Frequency depends on Most perennial weeds. More than one season required to species and climatic control some species; system may conditions. be combined with competitive crops and chemicals; follow local rec- ommendations. BROADLEAP WEEDS Amitrole (4)_ After harvest of crop Canada thistle, hoary Re-treat as necessary; frequently used but before Oct. 1. cress, leafy spurge, as spot treatment; check labels for poison ivy. restrictions as to crop species and for other precautions and instructions. SUGGESTED GUIDE FOR WEED CONTROL 196'9 35 TABLE 4.—Control oj perennial weeds in cropland injallow periods or by spot treatment—Continued Treatment Time of application Weeds controlled Remarks BROAD LEAF WEEDS—Continued Sil vex (3) Late fall or early spring. _ Smooth bedstraw. Usually re-treatment will be necessary; frequently used as spot treatment; check labels for restrictions as to crop species and for other precautions and instructions. 2,4-D (0.5-2). Actively growing foliage, Canada thistle, field Usually re-treatment will be neces- usually bud stage. bindweed, hoary cress, sary; observe treated areas and re- sowthistle. treat as required; check labels for restrictions as to crop species and for other precautions and instructions. 2,4-D (l-3)_ do- Bur ragweed, dogbane, Do. leafy spurge, Russian knapweed. Amitrole (4)_ In spring when Quackgrass. Till soil thoroughly 2 weeks after quackgrass is 4-10 application and before planting in. tall. any crop; check labels for restrictions as to crop species and for other pre- cautions and instructions. Atrazine or simazine Fall or spring before .do. Chemical residues in soil may injure (2-4) followed by planting corn. crops other than corn year after plowing and treatment; check labels for restrictions planting of corn. and other instructions. Dalapon (4-5) In spring when .do. followed by plowing quackgrass is 4-10 2 weeks later and in. tall. planting of corn 4 weeks after treatment. Spot spraying with During growing season Most grasses; oils will Add }i pt. surfactant to each 5 gal. dalapon (1) per 5 from hand applica-, also kill tops of spray mixture for herbicides mixed gal. water; or tors while weeds are broadleaf weeds; will in water; spraying lower 6 in. of aromatic oils. less than 15 in. tall; control but not weeds is usually adequate; check to foliage or stems eradicate perennial labels for restrictions as to crop of weeds. grasses. species and for other precautions and instructions. Dalapon (5-7) followed In spring when grass is Johnsongrass, Use followup program for seedling con- by disking after 2 15 in. tall or after trol ; check labels for restrictions as to weeks. clipping any time crop species and for other precautions when grass is this and instructions. height. EPTC (2-6). To freshly tilled soil in Quackgrass. Thoroughly work soil before and after early spring. application; check labels for restric- tions as to crop species and for other precautions and instructions. MH (4) followed by To foliage in early spring do. Corn or sugar beets may be planted as plowing in 4-8 days. soon as soil preparation is completed; not registered for use on other agronomic crops; check labels for re- strictions and other instructions. Amitrole (4). When weeds are 12- 18 Horsetail rush. Spray foliage; check labels for restric- in. tall. tions as to crop species and for other precautions and instructions. 36 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 4.—Control of perennial weeds in cropland in fallow periods or by spot treatment—^Continued Treatment Time of application Weeds controlled Remarks Amitrole (4) followed In spring; repeat as Purple nutsedge. Check labels for restrictions as to crop by disking after 2 needed for 2-3 years. species and for other precautions and weeks. instructions. Incorporate EPTC or In spring Purple and yellow nut- Check labels for restrictions as to crop vernolate (3) in soil. sedge. species and for other precautions and instructions. 2,4-D (1-2) 4-5 applications during Purple nutsedge_ Most effective where heavily fertilized growing season for 2 grasses can be grown in conjunction years. with herbicide treatment; check labels for restrictions as to crop species and for other precautions and instructions. WEED CONTROL IN HORTICULTURAL CROPS Weed control in horticultural crops is a highly ment of effective herbicides is providing the complex problem because of the large number of farmer with new technological tools of great different types of crops and their specific cultural, potential for use in combination with cultural and climatic, and soil requirements plus the many mechanical methods of weed control in horti- species of weeds associated with these environ- cultural crops. mental and cultural conditions. Horticultural Examples of herbicides presently in commercial crops include vegetables, deciduous tree fruits and use for horticultural crops are given in tables 5-10. nuts, citrus and subtropical fruits and nuts, small This information is intended to show the broad fruits, and ornamental plants. general areas of herbicidal effectiveness on these Several methods of weed control are used crops. Rate ranges are given, because specific separately and in various combinations in horti- rates vary with locality and depend on climate, cultural crops because of the complexity of the soil composition, and cultural practices. Excel- weed problem. Mechanical cultivation is usually lent weed-control recommendations based on local effective in controlling weeds between the rows but research have been prepared by many weed does not efficiently control weeds within the row specialists in State agricultural experiment sta- because of the proximity of weed and crop plants. tions. These recommendations are revised an- In periods of continued or excessive rainfall, nually to keep abreast of current research. These mechanical cultivation is impossible and the weeds sources provide specific herbicide and rate recom- normally controlled by this method overgrow the mendations for each locality. The reader should crop. Hand hoeing and hand pulling of weeds consult these specialists for specific rates and have been used to supplement mechanical cultiva- methods for safe and effective use on specific tion in many crops in the past. The scarcity and crops for local areas. cost of labor in recent years, however, have made Herbicides are selected on the basis of their hand weeding impractical in many instances and weed specificities. For example, one herbicide impossible in others. may be highly effective on germinating annual Cultural practices involving suitable rotation of weed grasses and ineffective on germinating broad- broadcast and row crops and crops of differing leaf weeds. Conversely, others may be effective growth habits can be used to limit the vigor and on only broadleaf weeds. The grower must spread of certain weeds. For example, sweet- therefore identify the weed and know its time potatoes are very strong competitors and can be of emergence and growth as a basis for selecting the used effectively in rotations to suppress weeds. correct herbicide and time of application. Broadcast-planted soybeans and sorghum are also The formulation to be used, whether granules effective smother crops for use in rotation. or spray, will depend on the weed problem. In The inefficiency of mechanical cultivation, the general, granules should be used in postemergence scarcity of hand labor, and the limitations of crop- or posttransplanting treatments after clean culti- rotation practices have stimulated intensive re- vation to take advantage of the physical selectivity search in chemical weed control. The develop- of this form as a means of minimizing injury to the SUGGESTED GUIDE FOR WEED CONTROL 196'9 37 crop. Granules may also be used as preplanting TABLE 5.—Weed control in vegetables—Continued and preemergence treatments as a matter of convenience. Pounds of DNBP, paraquat, PCP, and petroleum sol- Crop and herbicide active Time of application ingredient vents are very effective as directed sprays on per acre young rapidly growing weeds in many fruit and nut crops and ornamentals. Specific directions for Beans, lima: use under local conditions and a list of approved Amiben 2 Preemergence. crop uses can be obtained from State experiment CDAA 4 Do. station specialists. CDEC 6 Do. Calcium cyanamide is useful in controlling CIPC 2-6 Do. Dalapon 6 Spring preplanting germinating weeds and young emerged weeds in soil treatment plantings of many vegetable, fruit, and nut crops. 4-5 weeks before It is also a source of readily available nitrogen for planting. crops. Uses are specialized and local recommenda- DNBP (alkanola- 3-9 Preemergence. mine salt). tions should be obtained from State experiment Trifluralin 0.75 - - Preplant, soil in- station specialists. corporated. Beans, pole: VEGETABLES CIPC 2-6 Preemergence. Dalapon 6 Spring preplanting More than 50 vegetable crops are grown com- soil treatment mercially in the United States. Chemical weed- 4-5 weeks before control methods can fill a critical need in their planting. production. Examples of effective chemical EPTC 3 Preplant, pre- emergence, post- methods are given in table 5. emergence, soil incorporated. TABLE 5.—Weed control in vegetables Beans, snap: CDAA 4 Preemergence. [For herbicide tolerances, see Appendix] CDEC 6 Do. CIPC 2-6 Do. Pounds of Dalapon 6 Spring preplanting soil treatment Crop and herbicide active Time of application ingredient 4-5 weeks before per acre planting. DCPA 6-10.5 Preemergence. DNBP (alkanola- 3-9 Do. Artichokes, diuron 3.2 Apply in fall or mine salt). early winter EPTC . 3-4 ._ Preplant, pre- after final culti- emergence, post- vation. emergence, soil Asparagus: incorporated. Amiben 3 Preemergence. Trifluralin . 0.75 ._ Preplant, soil Dalapon 7-14 Preharvest, post- incorporated. harvest. Beets: Diuron 3.2 During winter dor- Endothall . 6.5 ._ Preemergence. mancy, early pre- Pyrazon - 4 __ Preemergence, post- emergence (at emergence; see least 4 weeks area restrictions before emergence), on label. or after harvest. Sodium chloride. _.. 200-300__ __ Postemergence. Monuron l-3.2_._ Preharvest, post- TCA (sodium 6-9 __ Preemergence. harvest. salt). Sesone 2-5.5_-_ Do. Broccoli: Simazine 2-4 Do. CDEC . 4-8 __ Preplant, pretrans- 2 Preemergence after plant, posttrans- disking in early plant. spring on estab- DCPA . 10.5 __ Preemergence, post- lished bed or transplant. after postharvest FW-925 . 6 __ Preemergence, post- disking. emergence, post- 2,4-D (sodium 1 Postemergence on transplant. salt). seedlings. Trifluralin _ 0.75-l__- __ Preplant, pretrans- 2.5 During harvest 2 plant, soil in- applications 1 corporated. month apart; Brussels sprouts : postharvest in CDEC _ 6-8 __ Preemergence, post- established ferns; emergence, pre- use drop nozzles transplant, post- for directed spray. transplant. 38 AGRICULTURE HANDBOOK 3 3 2, U.S. DEPT. OF AGRICULTURE TABLE 5.~Weed control in vegetables—Contmned TABLE 5.—Weed control in vegetables—Continued Pounds of Pounds of Crop and herbicide active Time of application Crop and herbicide active Time of application ingredient ingredient per acre per acre DCPA 10.5_-. Preemergence, post- Corn, sweet: transplant. Atrazine. _ 3-4 Preemergence at Trifluralin 0.75-1- Preplant, pretrans- planting time; do plant, soil in- not plant atrazine- corporated. sensitive crops in Cabbage: rotation. CDAA 4-6_ Preemergence, post- CDAA 4 Preemergence. transplant. CDAA plus 1.25 + 2.5_-_ Do. CDEC 4-8_. Preplant, preemer- TCBC. gence, pretrans- CDEC 6 Do. plant, posttrans- Cypromid- _ 1.5 __ Postemergence plant. directed spray DCPA 10.5_ Preemergence, post- when crop is 8 in. transplant. tall to lay-by; do FW-925 6-__. Preemergence, post- not feed foliage or emergence, stalks. posttransplant. Dalapon 1.5- Postemergence as Trifluralin 0.75-1. Preplant or pre- directed spray transplant, soil when corn is 8-20 incorporated. in. tall; do not use Cantaloup : on corn grown for CDEC 4 Preemergence. seed. DCPA 1Ö.5" Do. DNBP (alkano- 7.5-9 Preemergence. NPA (sodium 2-6_ Do. lamine salt). salt). Linuron 1-2.5 Do. Caraway, Stoddard (0- Preemergence, post- Propachlor 5 Preemergence; do solvent. emergence. not feed treated Carrots : forage. CIPC 2-6 Do. Simazine- 2-4 Preplant, preemer- DCPA 10.5 — Seed crop only at gence, soil in- planting or corporated. transplanting. [1.5 Preemergence on clay Linuron_ 1-2 Preemergence, post- I soils. emergence. 2,4-D_ \0.25-0.75— Postemergence be- Stoddard solvent (0 Do. fore corn reaches Cauliflower: 24 in. tall. CDEC 4-8 Preplant, preemer- 2,4-DEP_ 6 Immediately after gence, pretrans- planting. plant, posttrans- Cress, upland, CIPC. 2 Preemergence. plant. Cucumbers : DCPA 6-10.5_ Preemergence, CDEC 4 Do. posttransplant. NPA (sodium 2-6 Preemergence, post- FW-925 6 Preemergence, salt). transplant. postemergence, Dill, Stoddard (0 Preemergence, post- posttransplant. solvent. emergence. Trifluralin 0.75-1 _ Preplant, soil incor- Eggplant, DCPA 10.5 Transplant, lay-by. porated for trans- Endive, CDEC 4 Preemergence. plants. Escarole, CDEC 4 Do. Celery : Garlic : CDAA___ 4 ___ Posttransplant. CIPC 2-4 Preemergence, post- CDEC 4-6_ Preemergence, emergence. posttransplant. DCPA 6-10.5 Preemergence, ^^^^ 7 Posttransplant. transplant. Stoddard solvent-- (i) Preemergence, post- Hanover salad: ai • ^^^^ emergence. CDEC 4 Preemergence. Chicory, CDEC 4 Preemergence. CIPC 1-2 Do. C ollar ds : Kale: CDEC 4 Do. CDEC 4___. Do. CIPC 1-2 " Do. CIPC 1-2.. Do. DCPA 10.5 Do. DCPA 10.5- Do. Lentils : Barban 0.4 Postemergence for wild oats control; do not graze pea stubble. See footnote at end of table. See footnote at end of table. SUGGESTED GUIDE FOR WEED CONTROL 196'9 39 TABLE 5.—Weed control in vegetables—Continued TABLE 5.—Weed control in vegetables—Continued Pounds of Pounds of Crop and herbicide active Time of application Crop and herbicide active Time of application ingredient ingredient per acre per acre Diallate_ 1.5 Preplant, preemer- Diallate 1.3 Preplant, soil in- gence, soil in- corporated or corporated. preemergence, IPC___ 4 Preplant. soil incorporated; Lettuce: do not graze un- Benefin_ 1.1 Preplant, soil incor- harvested crop. porated ^-3 weeks DNBP (alka- Í6-9 Preemergence. before planting nolamine salt). 11.5-2 Postemergence. seed; observe label IPC - 4-8 Preplant, postemer- precautions on gence. feeding to livestock MCPA (amine or 0.75 Postemergence as and on crop sodium salt). prebloom. rotation. MCPB 0.25-0.75. _. Early postemergence. CDEC_ 2-4 Preemergence, pre- 2,4-DB 1.5 Apply when peas transplant. have 4-6 nodes of CIPC 3 Preemergence. growth before IPC 3-4.5 Do. blooming; do not Lettuce, head, 10.5 Apply 1-6 weeks graze or feed DCPA. after seeding. forage within 30 Lettuce, leaf, DCPA. 10.5 Apply 1-3 weeks days. after emergence. Peas, southern: Mint: DCPA 6-10.5 Preemergence. Diuron 1-2 Preemergence. Trifluralin 0.25-1 Preplant, soil incor- DNBP (alka- 3-4.5 Do. porated. nolamine salt). Peppermint : Mustard greens: Diuron 2.4 Last cultivation CDEC 4___. Do. before emergence. DCPA 10.5_ Do. Terbacil 0.8-1.6 Single preemergence Okra: application in CDEC 4 Do. spring after last Diphenamid 5 Preemergence at cultivation. planting. Peppers : Trifluralin_ 1 Preplant, soil Amiben 3-4 At transplanting or incorporated. lay-by. Onions : CIPC 6 Preemergence. CDAA 6 Preemergence, post- DCPA 6-10.5 Posttransplant. emergence. Diphenamid 5 Immediately after CIPC__ 4-8 Do. seeding or within DCPA. 10.5 Preemergence, post- 1 month after transplant. transplanting. KOCN_ 16-20 Preemergence, post- Trifluralin 1 Pr etr ansplant. emergence. Potatoes : Monuron 1.6 Do. CDAA 3-4 Preemergence, lay- Parsley, Stoddard (0 Preemergence. by. solvent. CDEC 3 Preemergence at Parsnips : planting. Linuron 1.5 Postemergence. Dalapon 3-11 Preplant, preemer- Stoddard solvent. (0 Preemergence, post- gence, lay-by. emergence. DCPA 6-10.5 At planting. Peas: Diallate 2 Preplant, soil incor- Barban 0.4. Postemergence for porated. wild oats control; Diphenamid 4-6 Immediately after do not graze pea planting. stubble. DNBP (alkanol- 3-6 Preemergence. CDAA_ 4___ Preemergence. amine salt). CIPC._ 4-6_ Preplant, preemer- EPTC 3-6 Preplant, soil incor- gence, soil in- porated, drag-off, corporated. lay-by incorpo- Dalapon 0.7. Apply after peas are rated. 2-6 in. tall and Linuron 1 Preemergence. have 4-6 nodes; Sesone 3.6 Premergence, post- do not apply within emergence, lay-by. 25 days of harvest; 2,4-D 2 Preemergence. do not feed vines 2,4-DEP 4 After clean cultiva- to livestock. tion at lay-by. See footnote at end of table. 40 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 5.—Weed control in vegetables—Continued DECIDUOUS TREE FRUITS AND NUTS Pounds of Many different cultural methods and combi- Crop and herbicide active Time of application nations of methods are used in deciduous tree ingredient fruit and nut crop production. Principal among per acre these are sod culture, strip sod and cultivation, and clean cultivation. Pumpkins : Herbicides are being used effectively on several Amiben 3-4 Preemergence. NPA (sodium 4 Do. of these crops. In certain of the nut crops, bare salt). soil culture is maintained with herbicida] oils. Sod Radish, CIPC__ 2 Do. culture is often combined with the use of herbicides Spinach: to control perennial woody and annual herbaceous CDEC 2-4 Preemergence, postemergence. weeds not controlled by mowing. Clean cultivation CIPC. 1-2 Preemergence. may be conveniently combined with herbicide IPC__ 3-6 Preemergence, post- treatments to control germinating weed seed and emergence. sprouting perennial weeds so as to extend the Squash, summer and periods between cultivations and thereby minimize winter : root and trunk injury. Amiben 3-4 Preemergence. DCPA 10.5-_ Apply 4-6 weeks Examples of herbicides that have proved useful after seeding on deciduous tree fruit and nut crop plantings in preceded by clean some regions are presented in table 6. They indi- cultivation. cate the general areas of usefulness of herbicides Sweetpotatoes : for these crops. Specific rates and methods for Amiben 3 At transplanting. safe and effective local use are available from CDAA 4 Pos ttransplant. weed research specialists in State agricultural DCPA 6-10.5- Do. experiment stations. Diphenamid_ 4-6 At transplanting. EPTC 7.5 Do. Tomatoes: TABLE 6.—Weed control in deciduous tree fruits and Amiben, 3-5 Postemergence after nuts clean cultivation. [For herbicide tolerances, see Appendix] 3 Preemergence to CDAA_ direct seeded. Pounds of 6 Within 2 days after Crop and herbicide active Time of application transplanting. ingredient CDEC_ 4-6 Preemergence, post- per acre transplant. CIPC__ 4 Postemergence at TREE FRUITS lay-by; granular formulation only. DCPA 10.5 Preemergence. Apples : Diphenamid_ AMS 154 In wetting spray to 4-6 Immediately after poison ivy in full seeding or within leaf. 1 month after Dalapon 11 As spot spray around transplanting. base of trees over Pebulate- 4 Pretransplant or 4 years old to posttransplant, control grass. soil incorporated. Dichlobenil 4-6 Early spring or after Trifl uralin _ 1 Preplant, soil in- clean cultivation. Diphenamid 6 After clean cultiva- corporated for tion but not within transplants or 90 days of harvest. postemergence on Diuron 3.2 Winter or spring. direct seeding. DNBP (butyl- 1.9 Coarse spray to Turnip greens: phenol). ground cover when CDEC__ 4 Preemergence. weeds are small. CIPC 1-2 Do. Simazine 2-4 In spring before DCPA 10.5 Do. weeds emerge. Turnips : Terbacil 1-3.2 Single directed spring CDEC application before 4 Do. weeds emerge in DCPA 10.5-. Postemergence. orchards estab- Watermelons, NPA 2-6 Preemergence, post- lished at least 3 (sodium salt). transplant. years. 2,4-D (acid or 2 Directed spray on oil-soluble young weeds, 50-100 gal. per acre. amine). See footnotes at end of table. SUGGESTED GUIDE FOR WEED CONTROL 196'9 41 TABLE 6.—Weed control in deciduous tree fruits and TABLE 6.—Weed control in deciduous tree fruits and nuts—Continued nuts—Continued Pounds of Pounds of Crop and herbicide active Time of application Crop and herbicide active Time of application ingredient ingredient per acre per acre TREE FRUITS—Continued TREE FRUITS—Continued Apricots : Dalapon 11 Spot spray on grow- Aromatic oil P) Directed spray on ing grass when emulsion. young growing weeds are small. weeds. Dichlobenil 4-6 Granules in early Dalapon___ 11 As spot spray around spring. base of trees when Diuron 3.2 Directed spray in weeds are small. winter or spring or Cherries : as split applica- Dichlobenil 4-6 Granules preemer- tion at 3/2 rate in gence to weeds. fall and spring. Simazine 2-4 Soil treatment in DNBP 1.9 Directed coarse late fall or early spray on ground spring on dormant cover. crop more than 1 Simazine 4 Directed spray dur- year old. ing dormancy on Olives : well-established Aromatic oil (2) Directed spray on trees. emulsion. young growing 2,4-D (acid or oil- 2 Directed spray on weeds. soluble amine). young weeds. Diuron 1.6 Split application fall Plums : and spring. Aromatic oil (2) Directed spray on Simazine 2-4 Broadcast single emulsion. young growing directed applica- weeds. tion to soil before Dalapon 11 Spot spray on grow- weeds emerge; ing grass when apply in late fall weeds are small. or midwinter. Dichlobenil 6 Granules in early Peaches : spring. Aromatic oil (2) Directed spray on DNBP 1.9 Directed coarse spray emulsion. young growing on ground when weeds. weeds are small. Dalapon 11 Spot spray on grow- Simazine (prunes) _ 4-6 For annual broadleaf ing grass when and grass weeds weeds are small. apply preemer- Dichlobenil 4-6 Granules in early gence or on clean spring. cultivated soil in Diphenamid 6 After clean cultiva- early spring; for tion, not within 90 perennials apply days of harvest. granule formula- DNBP (butyl- 1.9 Directed coarse tion only from phenol). spray to ground Nov. 15 to Jan. 1. cover when weeds are small. Simazine 4 As soil application TREE NUTS around established trees before weeds emerge; after har- Almonds, aromatic (2) Directed spray on oil emulsion. young growing vest to early spring. weeds. Terbacil 1-3.2 Single directed Walnuts, English: spring application Aromatic oil (2) Directed spray on before weeds emulsion. young growing emerge in orchards weeds. established at Diuron 4 Late fall or early least 3 years. spring in well- established plant- Pears : ings or as split AMS .-- 1 54 In wetting spray to applications in poison ivy in full late fall and early leaf. spring. Aromatic oil (2) Directed spray on emulsion. young weeds. 1 In 100 gal. water. See footnotes at end of tabli' 2 40-100 gal. per acre. 42 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE CITRUS AND SUBTROPICAL FRUITS AND TABLE 7.—Weed control in citrus and subtropical NUTS fruits and nuts—Continued Citrus and subtropical fruit and nut crops Pounds of include all citrus crops, avocados, dates, maca- Crop and herbicide active Time of application ingredient damia nuts, pineapples, and many other crops. per acre Weed problems are many and varied because of the wide distribution of these crops, their perennial Simazine 2-4_ Apply to orchard nature, and the variety of cultural practices used. floor before weeds Weeds waste irrigation water in plantings of many emerge, following of these crops. Weeds also harbor insects, dis- ñnal preparation eases, nematodes, and rodents that cause severe of grove. economic losses. 2.4 _ Directed spray after planting. Herbicides used in combination with mechanical Bananas, diuron_ 4.8_ Directed spray in cultivation are economical, effective, and conven- established plant- ient to use. In many instances damage caused by ings and repeat once after 6 weeks. close cultivation can be avoided and the periods be- Citrus (grapefruit, tween cultivations lengthened by using herbicides. lemons, oranges) : Aromatic oil emulsions have been used effec- Aromatic oil (0_ Directed spray on tively for more than 20 years in many citrus emulsion. young growing orchards in the West without reducing fruit yield weeds. ■8_ Restricted to com- and quality or visibly injuring the groves with mercial groves respect to tree physiology or soil structure. Newer established 2 years organic chemical herbicides have been devel- in Texas; use as single directed oped and are proving useful in areas where oils spot spray during cannot be used and on weeds not controlled by growing season oils. Many additional promising new herbicides each year for 2 are being investigated for use on these crops. years only; ob- serve all precau- Examples of herbicides that have proved useful tions on reuse and on citrus and subtropical fruit and nut crops in Bromacil (grape- crop rotation. some regions are presented in table 7. They show fruit, oranges). 6.4_ Restricted to Arizona the general areas of usefulness of herbicides for and California; use as single directed these crops. Specific rates and methods for safe spot spray from and effective local use are available from weed winter to early research specialists in State agricultural experi- summer in com- ment stations. mercial groves established 2 years; observe all precau- TABLE 7.—Weed control in citrus and subtropical tions on reuse and fruits and nuts crop rotation. Dalapon (grape- Directed spot treat- [For herbicide tolerances, see Appendix] fruit, limes, ment for grass oranges, tan- control. Pounds of gerines) . Crop and herbicide active Time of application Dichlobenil 4-6 _ Restricted to nursery ingredient and nonbearing per acre stock only; apply directed spray to soil and incor- Avocados : porate around Aromatic oil (i) Directed spray on crop established 1 emulsion. young growing or more years weeds. after transplant- Dichlobenil 6 Directed spray after ing. clean cultivation Diuron 1.6_ Soil treatment in in early spring. fall and spring in Monuron 1.6 Soil treatment in groves established spring and fall 1 year or more in under well-estab- Arizona and Cali- lished trees in fornia (selected California (se- areas only). lected areas only). See footnote at end of table. See footnote at end of table. SUGGESTED GUIDE FOR WEED CONTROL 196'9 43 TABLE 7.—Weed control in citrus and subtropical TABLE 7.—Weed control in citrus and subtropical fruits and nuts—Continued fruits and nuts—Continued Pounds of Pounds of Crop and herbicide active Time of application Crop and herbicide active Time of application ingredient ingredient per acre per acre During rainy season Bromacil 4.8 _ Use restricted to on established Hawaii; apply plantings of lemons immediately after Simazine_ in Arizona and planting; observe California. label precautions l9.6_ Oranges in Texas on crop rotation. and Florida. r6.4_ Immediately after f4-8_ Grapefruit and planting. oranges in Texas 1.6_ Postemergence and repeat at minimum only; single Diuron. directed spring of 2-month inter- application before vals using not weeds emerge in more than 12.8 groves established lb. per year. Monuron 1.6-3.2. Soil treatment im- TerbaciL at least 2 years. 3.2_ Arizona and Cali- mediately after fornia only; planting or after single directed harvest. spring application Simazine 3.2-4_ Do. before weeds emerge in groves established at 140-100 gal. per acre. least 2 years. Dates, aromatic oil (0- Directed spray on emulsion. young growing weeds. SMALL FRUITS Limes, aromatic oil (0- Do. emulsion. Macadamia nuts : Small fruits include cane fruits, cranberries, Dalapon 9__ On established grass grapes, and strawberries. Highly specialized before crop har- weed-control methods are required because of the vest and after gleaning nuts. different growth habits and stature and the Diuron 2-4_ Soil treatment; perennial nature of these crops. Many weed directed spray species must be controlled in summer and winter immediately after in many production areas. harvest. Simazine or 2-4 _ Soil treatment be- Parts of these crop plants are above ground atrazine. fore harvest and at all times. It has therefore become a general after gleaning nuts. practice to use directed, coarse, low-pressure Mangoes, dichlobeniL 6_ Directed spray in sprays that avoid herbicide contact with the early spring or after clean cul- crop wherever possible. In some crops, such tivation. as cranberries and strawberries, the use of directed Olives, diuron 1.6_ Directed spray in sprays is not possible. Here highly selective late fall and re- herbicides such as granular formulations are peated in early spring. most useful. Pineapples : Examples of herbicides that have been used Atrazine 6.4 _ Broadcast treatment successfully on small fruit crops in some production immediately after areas are given in table 8. Specific rates and planting or split application at 1-2 methods of application are not given, because month intervals climate, soil composition, cultural practice, and but not later than crop variety affect performance, selectivity, per- 160 days before sistence, and injurious effects of herbicides. harvest; observe label precautions Specific recommendations for safe and effective on feeding foliage local use of herbicides based on local research to livestock. are available from weed specialists in State See footnote at end of table. agricultural experiment stations. 44 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 8.—Weed control in small fruits TABLE 8.—Weed control in small fruits—Continued [For herbicide tolerances, see Appendix] Pounds of Crop and herbicide active Time of application Pounds of ingredient Crop and herbicide active Time of application per acre ingredient per acre l-2_ Soil treatment in dormant crop Blackberries : established at CIPC 2-6 Soil treatment in least 3 years. dormant crop. 4.8_ Directed spray in Í1-2 Soil treatment in well-established -p.. I dormant crop 1 plantings or 1.6 Umron year old or more. Diuron_ lb. per acre as [2.4 Directed spray in late split application winter or as split in late fall and application in late early spring. fall and spring. 9.6_ Directed spot spray in Simazine 2-4 During crop dor- established plant- mancy. ings on heavy soils Blueberries : once in 4 years. CIPC 6-12 Do. DNBP (alkano- 1.25_ Dormant application Diuron 1-2 Soil treatment in lamine salt). to ground under dormant crop 1 trellis. year old or more. Simazine 2-4_. Soil treatment from 2,4-D 3 Before burn during late fall to early dormancy. spring on crop Boysenberries, 2.4 Directed spray in established at diuron. late winter or as least 3 years. split application in Loganberries, 2.4_ Directed spray in late fall and spring. diuron. late winter or as Cranberries : split application CIPC 8_ Postharvest during in late fall and dormancy. spring. Dalapon 8.' Postharvest as di- Raspberries : rected spot spray CIPC 2-6 _ During crop on growing grasses. dormancy or at Dichlobenil 2-6 _ Granules, prebloom planting. or postharvest. 1-2 _ Soil treatment in Ferrous sulfate 800_ Spring to midsum- early winter on mer. dormant crop Simazine 2-4_ Soil treatment in established at least 1 year. dormant crop in Diuron. Massachusetts 2.4_ Directed spray in only. late winter or as During dormancy of split application crop; broadcast in late fall and before white bud spring. stage or apply Simazine 2-4_ During crop 0.25-percent dormancy. 2,4-D _ water solution on Strawberries : weeds with swab. Chloroxuron 4 Apply in fall after Broadcast during renovation of beds dormancy after and repeat once in drawing down spring at least 60 winter flood. days before /'l-2_ harvest. Soil treatment in CIPC l-3_ During dormancy dormant crop 1 to control year old or more established and in early winter. Gooseberries, diuron.^ 2.4_ germinating Directed spray in late chickweed. winter or as split DCPA 9___ Soil treatment after application in late transplanting or fall and spring. lay-by cultivation. Grapes : Diphenamid 6 After row establish- CIPC_ 10-14_ Directed spray in ment or 2-6 weeks early spring on after transplant- dormant crop. ing; 1 year before Dalapon 15_ Directed spot spray harvest only; do on growing grass not apply within during vegetative 60 days after growth of crop. harvest. SUGGESTED GUIDE FOR WEED CONTROL 196i9 45 TABLE 8.—Weed control in small fruits—Continued by the cost of material and time required for treat- ment. Comparatively low-cost selective herbicides Pounds of are therefore often used to control specific groups Crop and herbicide active Time of application of weeds. ingredient Examples of herbicides that are useful on per acre ornamentals in certain regions are presented in table 9. These examples indicate the general areas DNBP (amine 3-4.5 During dormancy in salts). early spring or of herbicide usefulness and their potential value after harvest in in these crops. Specific rates and methods for safe Northwestern and effective local use are available from weed re- States only. search specialists in State agricultural experiment EPTC 4 New beds—1 month stations. after planting ; old beds—fol- lowing clean cultivation after TABLE 9.^—Weed control in ornamental plants harvest. Sesone 3-4 Soil treatment after transplanting and Pounds of postharvest avoid- Herbicide active Tolerant plants ing flowering and ingredient fruiting period. per acre Simazine 1 3-4 weeks after planting. 2, 4-D 1.5 Spray young growing CDEC 4-6_ - _ Use directed spray or granules weeds after on soil in established orna- harvest. mental plantings: Azalea, 2,4-DEP 4 Preplant or post- euonymus, gladiolus, iris, transplant in juniper, Poteniilla, privet, nonharvest year; spirea, yew. postharvest in CIPC 6-10_ ._ Use directed spray or granules production fields. on soil in established plantings: Arborvitae, aster, Astilbe, azalea, balsam, barberry, birch, bluebell, boxwood, camellia, carna- tion, cedar, chrysanthemum, ORNAMENTAL PLANTS columbine, coralbell, creep- ing juniper, dahlia, Ornamental plants, including shade trees delphinium, dianthus, shrubs, herbaceous annuals and perennials, and Dutch iris, English ivy, bulb crops, form the bulk of plant species in horti- forget-me-not, forsythia, fuchsia, gladiolus, honey- cultural crops. Some ornamental genera include suckle, hydrangea, laurel, numerous species and many varieties. Weed prob- lilac, lily, magnolia, lems are widely different because of the mdividual Mahonia, maple, mock- soil, climatic, and cultural requirements of many orange, narcissus, pachy- sandra, peony, periwinkle, of these plants. The number of herbicides available poplar, privet, rhododendron, for home or other landscaped plantings is limited rose, spirea, tulip, viburnum, because many kinds of plants are grown together. wintercreeper, yew. Weeds in commercial plantings of individual DCPA 10-15. . _ Use directed spray or granules on soil in established orna- species or varieties are controlled by mechanical mental plantings: Ageratum, cultivation, hand weeding, herbicides, cultural alyssum, aster, azalea, practices including rotations, and various com- babysbreath, barberry, binations of these methods. bleedingheart, candle lark- spur, chrysanthemum, Ornamental plant families, genera, species, and coleus, columbine, coralbell, even varieties respond differentially to herbicides. dahlia, euonymus, evening- Great care is therefore necessary in selecting and primrose, feverfew, forget- using herbicides on them. As a result, soil fumi- me-not, forsythia, gladiolus, golden marguerite, lantana, gant herbicides are used in many nurseries. Soil lupine, marigold, moss rose, fumigant herbicides are applied, kill many annual mourning bride, mourning and perennial weeds, and are dissipated before pinks, petunia, pokerplant, planting the crops. Most crops can be planted purple coneflower, rose, salvia, scarlet sage, snap- within a few days after fumigants have been used. dragon, variegated privet, General use of soil fumigant herbicides is restricted verbena, yew, zinnia. 46 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 9.—Weed controlin ornamental plants—Con. TABLE 9.—Weed control in ornamental plants—Con. Pounds of Pounds of Herbicide active Tolerant plants Herbicide active Tolerant plants ingredient ingredient per acre per acre Dichlobenil 4-6 (an- Use spray or granules in NPA (sodium 4-6. Use directed spray or granules nual nursery or landscape plant- salt). on soil in established orna- weeds) ; ings; do not treat within 4 mental plantings : Azalea, 6-8 weeks of transplanting: cottonwood, holly, maple, (peren- Amur corktree, arborvitae, plum, rhododendron. nial ash, azalea (kurume, mollis, Sesone 3-3.6- Use directed spray or gran- weeds). hardy hybrid types, and ules on soil in established hardy native species only), plantings: Arborvitae, bal- barberry, beautybush, birch, sam, barberry, bayberry, boxelder, boxwood, camellia, camellia, cedar, crabapple, Caragana, Cleyera japónica, daffodil, dahlia, elm, for- cotoneaster, cottonwood, sythia, gladiolus, heather, crabapple, deutzia, dogwood, hemlock, honeysuckle, hy- eastern red cedar, elm drangea, iris, juniper, (American, Chinese), El- laurel, lilac, lily, maple, wood cypress, euonymus, mockorange. Picea, pine, flowering almond, flowering redcedar, rose, spirea, quince, forsythia, gardenia, spruce, viburnum, white golden-rain-tree, hackberry, birch, yew. heather, holly (except Ilex Simazine 2-3 _ Use directed spray on soil in crenata L., rotunda L., established ornamental vomitoria Ait.), honeysuckle, plantings: American elm, ivy, juniper, kinnikinnick, arborvitae, Austrian pine, laurel, leucothoe, lilac, linden, barberry, blue spruce, box- locust, magnolia, maple, elder, boxwood, bush- mockorange, mountain-ash, honeysuckle, Caragana, nandina, Qak, osmanthus cotoneaster, dogwood, (hoUyolive), pachistima, Douglas-fir, Fraser fir, hem- photinia, pine, pittosporum, lock, honeylocust, juniper, podocarpus, poplar, privet, Mahonia, mugo pine, pyracantha, rhododendron, multiñora rose, Norway rockrose, rose, Russian-olive, spruce, redcedar, red oak, spirea, spruce, squawcarpet, red pine, red spruce, rose, viburnum, weigela, willow, Russian-olive, Scotch pine, yew. Siberian elm, white-cedar, Diphenamid-- 4-6 Use directed spray or granules white pine, white spruce, on soil in established orna- yew. mental plantings : Evergreen, Stoddard (0- In directed spray on emerged deciduous trees. solvent. weed seedlings between DNBP (alka- 10.5 Use directed spray or granules rows: Most ornamentals. nolamine on soil in established orna- Trifluralin 0.5-1. In directed spray or granules salt). mental plantings : Dahlia, on soil in established plant- Dutch iris, gladiolus, lilac, ings of gladiolus, many lily, narcissus, privet, spirea, other ornamentals. tuHp, yew. Neburon 4 Use directed spray or granules on soil in established plant- 50-100 gal. per acre. ings: Arborvitae, Chamae- cyparis, euonymus, firethorn, forsythia, honeysuckle, juniper, pine, privet, yew. WEED CONTROL IN HORTICULTURAL Plants involved include tomatoes, peppers, egg- PLANT BEDS AND NURSERIES plant, celery, petunias, marigolds, and many other vegetable and ornamental plants. The growing of vegetable and ornamental Large numbers of ornamental plants are vege- transplants in plant beds and nurseries is a major tatively propagated from cuttings. Weeds are horticultural industry. Seeds are planted in difficult and expensive to control in slathouses, open fields in the South and in hotbeds in the coldframes, and liner plantings in the field. cooler areas. High rates of seeding are used and Plants propagated vegetatively include azaleas, weeds that emerge with the crops cannot be re- camellias, rhododendrons, pyracantha, and holly. moved mechanically. Weed separation and re- Weed seed and the underground parts of moval by hand are diflBcult and time consuming. perennial weeds in coldframes, hotframes, and SUGGESTED GUIDE FOR WEED CONTROL 196i9 47 slathouses are usually controlled by soil fumiga- Soil fumigant herbicides and their use are de- tion. Field plantings of large populations of plants scribed briefly in table 10. Specific details for often include soil fumigation as a preparatory effective use of fumigants under local conditions measure. Cultural practices, including selected are available from weed research specialists in rotation procedures, should supplement the use of State agricultural experiment stations. herbicides. WEED CONTROL IN GREENHOUSES TABLE 10.—Weed control with sou fumigant herbi- Weeds in greenhouse bench and potting soils cides in horticultural plant beds and nurseries and under the benches generally can be controlled with herbicides and by steam sterilization. Pounds of Weeds in bench and potting soils can be con- active Method of application after trolled with soil fumigant herbicides, such as Herbicide ingredient preparation of soil for planting per 100 methyl bromide or SMDC, before the soil is sq. ft. brought into the greenhouse or potting room. Rates and methods of using these herbicides are briefly described in the preceding discussion on 9.8_ Plant beds; use split applica- tion to newly worked soil weed control in plant beds and nurseries. Specific 90 days before planting or details for use are given by the manufacturers, 60 days before freezing in and information on techniques for specific prob- fall; work first half of lems can be obtained from weed research specialists treatment into top 3 in. of Calcium soil and rake second half of in State agricultural experiment stations. cyanamide. treatment into surface Weeds under the benches and around pots in the layer of soil. benches can be controlled by using a coarse spray i6.1_ Compost and top soil; mix of Stoddard solvent. The weeds should be small thoroughly with moist screened compost as it is at the time of treatment. A complete spray placed in soil bin or pile; coverage of the weed foliage is necessary. Direct wait 6 weeks before using. the spray to avoid contact with the foliage or Methyl l-2_ Cover soil with plastic sheet, stalks of crop plants or move the pots from the bromide. inject methyl bromide under plastic, allow soil to bench area during spraying. Keep fresh air remain covered 24-48 moving into the greenhouse during treatment and hours, remove cover, and for 2 to 4 hours thereafter. aerate 72 hours or longer Great care must be exercised to avoid crop before planting. SMDC 0.7-l__. Apply with sprinkling can or injury when herbicides are used in maintenance hose proportioner; mix programs in greenhouses. Crop injury may result herbicide to depth of 5-6 from using volatile herbicides that produce in. ; sprinkle-irrigate im- generalized effects on all plants or from persistent mediately to desired depth of control; plant 14-30 herbicides that remain in soils for long periods. days after treatment de- Stoddard solvent is suggested for greenhouse use pending on soil composition because it avoids these hazards. It will kill many and moisture content. species of young growing broadleaf weeds and weed grasses within a few hours after application 1 Per cubic yard. and does not leave a chemical residue. WEED CONTROL IN FORAGE CROPS, PASTURES, AND RANGELANDS Weeds, including brush, are undesirable in true for many annual weeds developing from forage crops and grazing lands because they new seedlings each year. reduce production of palatable forage, some Some weed species, however, are favored by injure livestock through needles and thorns, the same conditions responsible for vigorous many are poisonous, others impart undesirable growth of forage plants; for example, curly dock flavors in milk, and in general they reduce the and chickweed are favored by high fertility in quantity and quality of animal products. Im- humid regions. Woody plants tend to dominate proved crop-production practices, including proper the vegetation and must be removed to achieve fertilization, drainage of soils where necessary, efficient production of forage. Most woody plants judicious mowing and grazing practices, and will not yield to ordinary management practices. disease and insect control, contribute to the In addition, many persistent perennial weeds vigor of forage plants, which, in turn, aid in will not succumb to the known agronomic prac- preventing weed problertis and in some cases will tices within a reasonable time. Often mechanical reduce weed populations. This is particularly methods are used to control woody weed species. 48 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE Fortunately selective herbicides are now avail- normally required. Where native grasses are able that will aid in dealing with many of these present, it is almost always desirable to defer the problems. By killing unwanted species, they may grazing during the growing season for 1 or 2 years. hasten the succession to more desirable plants. Correct timing of herbicide application in By selective control of the undesirable species, relation to growth stage of weeds and during along with improved grazing practices, the re- periods of adequate moisture in the soil may covery of native forage plants and other desirable determine whether the treatment will succeed or species may be greatly speeded. Many pastures fail. This varies with individual weed species. and rangelands are so depleted of desirable Check on correct timing with agricultural species that a long time would be required for specialists. natural succession to take place if only improved Annual weeds usually are most easily killed grazing management is practiced. Here seeding with herbicide foliage sprays while they are small. adapted forage species may be necessary. However, more nearly adequate control often The herbicides MCPA, silvex, 2,4-D, and results if spraying is delayed until germination 2,4,5-T are not poisonous to livestock, wildlife, and emergence of such weeds are mostly com- or man at the application rates used to control pleted. Such delays may result in a higher overall weeds in forage crops, pastures, and rangelands percent control than if the treatments were and do not injure most forage grasses. If no applied earlier at the most susceptible stage of poisonous plants are present in the treated area, the early germinating weeds, because weeds livestock other than milk cows need not be germinating after spraying with the phenoxy removed during or after application. Milk cows herbicides are largely unaffected. should be removed from the pastures for a week The most susceptible stage for perennial weeds after spraying because of possible residues in the varies greatly with the species and climatic condi- milk. If poisonous weeds or poisonous woody tions. Many perennial weeds are most susceptible plants are known to occur in pastures or on range- when actively growing and at the late vegetative lands, remove the livestock from the area for at or early bud stages. However, some species, such least 3 weeks after treatment. Several herbicides, as deathcamas and wild garlic, are most susceptible including MCPA, 2,4-D, and 2,4,5-T, are known much earlier in their life cycle. Also, environmental to produce marked changes in the chemical conditions critically affect responses of species to composition of treated plants. Some herbicides herbicides. Therefore, details for controlling indi- aiïect the palatability of certain plants, and vidual species usually should be obtained from livestock will graze some treated species that they local agricultural authorities. normally would not eat. For further information on the control of many Single applications of foliage sprays will often range weeds, see the handbook on ^'Chemical control mesquite, sand sagebrush, big sagebrush, Control of Range Weeds,^^ U.S. Department of perennial ragweed, and other weeds on permanent Agriculture and U.S. Department of Interior, pastures and rangelands. However, repeated issued December 1966. The relative susceptibility of many common woody species to herbicides is treatments are usually needed for most woody given in U.S. Department of Agriculture Farmers' plants and perennial weeds (table 11). For Bulletin 2158, ^^Chemical Control of Brush and satisfactory control of mixed stands of oak species Trees.'' Also, the relative susceptibility of many and buckbrush, for instance, repeated annual weeds to 2,4-D, MCPA, 2,4,5-T, silvex, and applications for 2 or more years, with not more 2,4-DB is tabulated in Farmers' Bulletin 2183 than 2 years intervening between treatments, are ''Using Phenoxy Herbicides Effectively." TABLE 11.—Weed control in forage crops, pastures, and rangelands [Numbers in parentheses=pounds of active ingredient per acre unless otherwise indicated; for herbicide tolerances, see Appendix] Crop and treatment Time of application Weeds controlled Remarks FORAGE CROPS Alfalfa and birdsfoot trefoil : New seedings: CIPC (2) Postemergence, late fall Chickweed- Do not use if grass is planted with or early winter. legume. Dalapon (2). 4 weeks after seeding or Crabgrass, foxtaiL Stunts alfalfa temporarily ; repeat when grasses are less treatments later in summer; no in- than 3 in. tall. jury to trefoil; do not feed first year's growth to dairy cows or animals being finished for slaughter. SUGGESTED GUIDE FOR WEED CONTROL 19619 49 TABLE 11.—Weed control in forage crops, pastures, and rangelands—Continued Crop and treatment Time of application Weeds controlled Remarks FORAGE CROPS—continucd DNBP (0.75-1.5)___ When weeds are small Chickweed, henbit, Often injures birdsfoot trefoil; use in and legume seedlings pepperweed, weed alfalfa or alfalfa-grass mixtures only; have 2 or more true bromegrass. do not use forage for livestock for leaves. 60 days after treatment. DNBP amine salts After emergence of Bitterweed, lambs- Injures trefoil. (0.75-1.5) in 20- alfalfa seedlings when quarters, mustard, 40 gal. water. weeds are small. pigweed, ragweed, sneezeweed, tarweed. EPTC (2-4) Immediately before Weed grasses, some Mix with soil by disking or vigorous planting alfalfa or broadleaf weeds. harrowing; herbicide volatile, lost birdsfoot trefoil. if applied on wet soil or allowed to remain on surface for short time; highest rate required for nutsedge control. 2.4-DB amine salt Postemergence when Broadleaf weeds Can be applied at later stage of or esters (0.75- weeds are less than 3 growth than DNBP; do not graze or 1.5) in 5-20 gal. in. tall, feed treated plants to livestock water. within 30 days after application. Estabhshed stands: CIPC (2) In fall when legumes are Ohickweed dormant and weeds small. Diuron (1.6-2) In fall after crop is Annual weeds in North- Stands must be at least 1 year old. dormant or early western States, spring. Diuron (3) do Downy bromegrass Do. DNBP amine salts In fall when legumes are Chickweed, henbit, yel- Re-treatment in late winter or early (2) in 20-40 gal. dormant and weeds low rocket seedlings, spring necessary for heavy water. small. ^ . . , „ ^ infestations. 2,4-D or MCPA Early dormant stage of sensitive broadleaf Use only as emergency measure if ' (0.1-0.25). legume. weeds. weed infestation threatens crop. Alfalfa: ^ ^_, CIPC (6) (granular) _ _ Before or during dodder Dodder Timing critical.^ emergence and/or after first cutting. Weed burner Stubble following first do Kill top growth with light flame; burn cutting. patches clean when vegetation has dried. Clovers—alsike, crim- son, ladino, red, and white—new seedings : CIPC (2) Late fall or early winter. _ Chickweed. Do not use if grass is mixed with clover. CIPC, EPTC, or Immediately before Weed grasses, some Disk into soil before weed germina- IPC (4). planting clover. broadleaf weeds. tion. IPC (4) Postemergence when do Do not use if grass is mixed with clover has at least 3 clover. true leaves. Clovers—ladino, red, and sweet: New seedings: DNBP (0.75-1.5) When weeds are small Chickweed, henbit, Do not graze treated areas or feed in 20-40 gal. and clovers have 2 or pepperweed, weed treated forage to livestock before water. more true leaves. bromegrass. first cutting. DNBP amine salts After emergence of clover Bitterweed, lambs- Do. (0.75-1.5) in 20- seedlings when weeds quarters, mustard, 40 gal. water. are small. pigweed, ragweed, sneezeweed, tarweed. 2,4-DB (1-1.5) in Postemergence when Broadleaf weeds Can apply at later stage of legume 20-40 gal. water. weeds are less than 3 growth than DNBP. in. tall. See footnote at end of table. 50 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 11.—Weed control in forage crops, pastures, and rangelands—Continued Crop and treatment Time of application Weeds controlled Remarks FORAGE CROPS—continued Established stands: CIPC (2) In fall when clovers are Chickweed. dormant and weeds small. DNBP amine salts do Chickweed, henbit, Re-treatment in late winter or early (2) in 20-40 gal. yellow rocket seedlings. spring necessary for heavy infesta- water. tions. 2,4-D or MCPA Early dormant stage of Sensitive broadleaf Use only as emergency measure if (0.1-0.25). clover. weeds. weed infestation threatens seed crop. PASTURES AND GRASS-SEED FIELDS Grasses : New seedings: Summer fallow 1 year before planting Perennial weeds including Reduce or eradicate these species grass. bermudagrass, Canada before planting grasses. thistle, Johnsongrass, quackgrass. Thorough tillage in 1-2 years preceding Annual broadleaf weeds, Where winter annual grasses are intertilled crops. planting grass. annual grasses. problem, delay grass seeding until after last hard freeze in spring if rainfall or irrigation is sufficient to establish seedlings before heat and summer drought start. Sil vex (0.5-0.75) After grass seedlings Chickweed, henbit, Do not exceed 0.5 lb. per acre until have reached 2-4 leaf knotweed. grasses become well established. stage. 2,4-D amine salts do Broadleaf weeds If land is heavily infested with seeds or esters (0.75). of annual grasses, delay application until broadleaf weeds are 12-15 in. tall to aid in preventing germination of weedy grasses; do not add surfactants. Sprigged stands of Just before or just after Annual broadleaf and Use 1.5 lb. of herbicide per acre on bermudagrass, sprigging before weeds weed grasses. sandy soil; delay grazing or hay simazine or diuron emerge. harvest at least 5 months after (3.2). treatment. Seed fields: CIPC or IPC (3-4) _ Late fall (before Oct. 15) Winter annual weeds in Especially effective on winter annual Northwestern States. grasses; too late application will reduce seed yields. Dicamba (0.25-0.75) Single leaf. Most winter and spring Grass may be temporarily injured; use broadleaf weeds. on seed crop only. Diuron (2-3) Late fall, established Winter annual weeds in- Do not use on light sandy soils. fields. cluding bromegrass. Pastures : Renovation on soils Late summer Sod, weed grasses Graze turf heavily during summer, too hilly or stony then kill undesirable grasses; disk to be plowed, dead sod 3-5 weeks after treatment dalapon (7.4). and seed; control broadleaf weeds by selective herbicides in new seed- ing with 2,4-D or 2,4,5-T. PERMANENT PASTURES AND RANGELANDS Pastures : Fertilize adequately, Broomsedge_ Consult local authorities for recom- mow when grass mended rates and times of fertilizer becomes coarse, application. graze area in- tensively. SUGGESTED GUIDE FOR WEED CONTROL 19 619 51 TABLE 11.—Weed control in forage crops, pastures, and rangelands—Continued Crop and treatment Time of application Weeds controlled Remarks PERMANENT PASTURES AND RANGELANDS Continued 2,4-D amine salts or Usually late spring. Burdock, Canada thistle, Spray while weeds are actively grow- esters (0.5-1). chicory, common ing; in humid area where legumes broomweed, dandelion, are in pasture, delay treatments ironweed, pigweed, until initial rapid growth of legumes ragweed, sneezeweed, has passed; remove milk cows from tarweed. pasture for 7 days after spraying. 2,4-D esters (1-2) _. Between February and Common broomweed, If second application is necessary, May. curly dock, hore- treat between October and Decem- hound, wild garlic, ber; remove milk cows from pasture wild onion. for 7 days after spraying. 2,4,5-T amine salts Fall, winter, or spring. _ Bedstraw, chickweed, These herbicides kill lespedeza and or sil vex (1-2). henbit, knawel. seriously injure true clovers; remove milk cows from pasture 7 days after spraying. Rangelands : Silvex low-volatile May 15-June 30_ Yucca esters (0.7). Silvex low-volatile Early bloom Dalmatian toadflax Seedlings may require re-treatment in esters (3). 2-3 years. Silvex or 2,4,5-T low- Full leaf stage and grow- Shinnery oak Tops killed with 1 application ; to volatile esters ing actively. reduce stands make 2-3 annual ap- (0.5-1). plications; in drought years or if foliage damaged by frost, defer spraying until next year. Cultivation by disk After emergence of full Downy brome and as- Treatment in preparation for spring harrow or disk stand of weeds in sociated broadleaf seeding or for fallow and fall seeding plow. spring. weeds, e.g., Russian of perennial grasses, e.g., crested thistle, tansymustard, and intermediate wheatgrasses ; tumble mustard. seeding in furrows will increase seed- ing success; spring seeding should not be attempted after Apr. 15. 2,4-D, undiluted Any time. Hardwood species more Tree injector or other injecting equip- than 1 in. in diameter. ment; apply in cuts 2 in. apart at base of tree. 2,4-D (1.5-2) in 3-5 After spring growth and Big sagebrush, low sage- Properly timed mowing also controls gal. oil, water, or before soil moisture is brush. sagebrush; can be done where ter- oil-water emulsion. depleted in upper rain is not too rough or rocky. 8-10 in. 2,4-D (3) in 5 gal. oil New twig growth 3 in. Rabbitbrush. More difficult to control than sage- or oil-water or longer and before brush; do not apply when soil emulsion. soil moisture is de- moisture is critically low. pleted in upper 8-10 in. 2,4-D esters (1) in In May or early June Sand sagebrush Diesel oil preferred for lowest 1-4 gal. water, with 6-8 in. of new gallonage. diesel oil, or oil- growth. water emulsion. 2,4-D esters (1-2) in After full foliage (usu- Buckbrush Repeated annual sprayings may be 3-4 gal. water, ally last part of May). necessary; correct timing important. diesel oil, or oil- water emulsion. (Early spring, 3- to 5- Deathcamas Spraying ineffective if treatment is leaf stage. delayed. 2,4-D esters (1.5-3). Fully emerged but be- Low larkspur Do not graze sprayed areas for at fore flower stems least 3 weeks after treatment. appear. 'Bud to early bloom Locoweed, princesplume. Repeated annual applications may be stage. silvery lupine, two- necessary; do not graze sprayed grooved milk vetch, areas for at least 3 weeks after 2,4-D esters (2). waterhemlock, woody treatment, aster. .Early bolting stage. _ Tansy ragwort 2,4-D esters (3) Prebloom stage Orange sneezeweed 2,4-D low-volatile Early branching, pre- Halogeton Provides 1-year control ; halogeton esters (2). bloom stage. reinfests next year unless other plants occupy site; near trails and bed grounds. 52 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE TABLE 11.—Weed control in forage crops, pastures, and rangelands—Continued Crop and treatment Time of application Weeds controlled Remarks PERMANENT PASTURES AND RANGELANDS Continued 'Full leaf stage after Post oak_ Mixture may be used if 2,4,5-T makes rapid growth. up at least % of mixture and use of 2,4-D is not hazardous; re-treatment 2,4,5-T esters (1) within 2 years is necessary ; re-treat plus2,4-D (2). for 1 or 2 consecutive years. Actively growing plants Timberline milkvetch__ in late vegetative or early bud stage. 2,4,5-T esters or Full leaf stage after Blackjack oak, post oak__ Re-treat for 2-3 consecutive years. silvex (2). rapid growth. 2,4,5-T esters or Late vegetative growth Tall larkspur Repeated annual applications neces- silvex (3-4). but before flower buds sary; do not graze sprayed areas for form. at least 3 weeks after treatment. 2,4,5-T low-volatile After leaves full size and Velvet mesquite Re-treat within 2 years. esters (0.3). terminal elongation stopped. 2,4,5-T low-volatile 50-90 days after first Honey mesquite Tops killed ; re-treatment necessary in esters (0.5). leaves appear in spring. 5-7 years. 2,4,5-T low-volatile When soil is dry Agarita, catclaw, elbow- Apply to frills, stumps, or basal esters (8) in 100 gal. bush, huisache, mes- trunks. diesel oil. quite. 2,4,5-T low-volatile Basal spray summer or Baccharis, bay berry. Do. esters (12-20) in winter. beech, birch, Ceano- 100 gal. diesel oil. thus, chestnut, chinka- pin, cottonwood, hack- berry, honeylocust, hydrangea, madrone, manzanita, mescal- bean, mulberry, nar- rowleaf spirea, osage- orange, pecan, prick- lyash, red haw, retama, sassafras, silver maple, spicebush, sumac, tree- of-heaven, walnut, wild chinaberry, willow. 2,4,5-T low-volatile Summer or winter. Ash, blackgum, blackjack Do. esters (16) in 100 oak, bur oak, elm, gal. diesel oil. hickory, pin oak, post oak, red maple, red oak, sweetgum, sycamore, water oak, white oak, willow oak. 2,4,5-T low-volatile Any time- Hardwood species more Tree injector or other injectmg equip- esters (32) in 100 than 1 in. in diameter. ment; apply in cuts 2 in. apart at gal. diesel oil or base of tree. undiluted. 2,4,5-T or silvex low- When plants are growing Cholla cactus, prickly- Wetting spray, volatile esters (8) rapidly. pear, tasajillo. in 100 gal. diesel oil. 1 See U.S. Department of Agriculture Farmers' Bulletin 2211, ''Controlling Dodder in Alfalfa." WEED CONTROL IN LAWNS AND OTHER TURF AREAS Good turf care, including proper liming, fertil- lems will usually be disappointing. Vigorous turf ization, watering, proper height and time of is required to fill in the bare spots remaining after cutting, and control of insects and diseases, weeds are controlled. In addition, a vigorous should accompany any program of weed control dense turf will greatly aid in preventing rein- in lawns and other turf areas. Controlling weeds festation. without correcting other lawn management prob- Table 12 contains information about herbicides SUGGESTED GUIDE FOR WEED CONTROL 196i9 53 that may be used to control weeds in lawns and to phenoxy herbicides, see U.S. Department of other turf areas. Follow explicitly all directions Agriculture Home and Garden Bulletin 123, on the container label. For further information 'iawn Weed Control With Herbicides,'^ and on controlling 1-awn weeds with herbicides and Farmers' Bulletin 2183, ''Using Phenoxy Her- for data on the susceptibility of many lawn weeds bicides Effectively.'' TABLE 12.—Weed control in lawns and other turf areas [Numbers in parentheses = pounds of active ingredient] Crop and treatment Time of application Weeds controlled Remarks NEW SEEDINGS Methyl bromide (1) When soil temperature is Weed grasses and broad- Well-prepared, moist seedbed; apply per 100 sq. ft. above 65° F. leaf weeds—all plant under gastight cover; follow manu- parts including seeds facturer's instructions; seed lawn and seedling parts; 2-3 days after application; this soil also disease organisms, fumigant is deadly poison; follow nematodes, insects. directions on label. Siduron (0.25) per 1,000 Before weed-grass germi- Crabgrass, other annual Treat before, during, or after seeding; sq. ft. nation. grasses. water within 3 days if no rain; use only on bluegrass and fescue lawns. ESTABLISHED LAWNS (wiTH WEED GRASSES) Benefin (1.5) per acre. Before weed emergence Crabgrass _ Do not overseed within 3 months after treatment. Bensulide, 4-5 oz. per do do____ Do not overseed within 6 months 1,000 sq. ft. after treatment. ('Spot treatment when Clumps of nimblewill, Will injure all grasses in treated spot; grasses are actively orchardgrass, quack- carefully treat weeds ; if applied in Dalapon (0.25) in 1 gal growmg. grass, timothy. warm moist soil, possible to reseed water per 1,000 sq. < in 3-6 weeks. ft. July; repeat 3-4 weeks Bermudagrass Lawn grasses also killed by treatment; later; water between reseed 3 weeks after second appli- applications. cation if temperatures are high, 6 weeks if temperatures are low; if soil is dry, water thoroughly before seeding. DCPA (0.25) per 1,000 Early April before weed Crabgrass. Follow instructions on label. sq. ft. emergence. DSMA and similar After weed-grass emer- Crabgrass, dallisgrass, Follow instructions on label; may arsonates (1.5-2.5) gence; re-treat at 7- to goosegrass, sandbur. slightly discolor turf. per acre. 10-day intervals until control is obtained. Petroleum naphtha, 1 Spot treatment when Clumps of nimblewill, Carefully treat weeds; also will kill gal. per 1,000 sq. ft. grasses are actively orchardgrass, quack- lawn grasses. (use full-strength growing. grass, timothy. coarse spray). SMDC (0.5-1) per 100 Early August; repeat Bermudagrass Follow manufacturer's directions; sq. ft. 4-6 weeks later. reseed 3-4 weeks after second application. ESTABLISHED LAWNS (WITH BROADLEAF WEEDS) Dicamba (0.25) per acre. When weeds are actively Chickweed, clover, Do not exceed recommended rate; growing. henbit, knotweed, stay away from shrubs and other purslane, red sorrel. ornamental plants. Endothall (2) in 50-100 When plants are small Burclover, henbit, knot- May discolor foliage of ryegrass and gal. water per acre. weed, pennywort. bluegrass; keep children and animals off sprayed areas until after first rain or sprinkling. Silvex (1-1.5) per acre Actively growing weeds. Burclover, chickweed, Spray area overall; or to spot treat, or 0. 4-0. 5 oz. per ground ivy, henbit, fasten piece of kitchen sponge to 1,000 sq. ft. knotweed, pennywort, end of stick or broom handle, dip violet, white clover, sponge into solution, spot treat woodsorrel. broadleaf weeds by pressing moist sponge against crown of each plant; delay mowing 24-48 hours. 54 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 12.—Weed control in lawns and other turf areas—Continued Crop and treatment Time of application Weeds controlled Remarks ESTABLISHED LAWNS (WITH BROADLEAF WEEDS) Continued 2,4-D (0. 5) plus silvex When weeds are small Chickweed, clover, Do not allow spray to drift onto (0. 5) low-volatile in cool weather or henbit, knotweed, red trees and shrubs. esters per acre. early spring. sorrel. 2,4-D (1) plus dicamba When weeds are small. do Do not exceed recommended rate and (0.25) amine salts per avoid flowers and shrubs; esters and acre. amines not compatible. 2,4-D amine salts or Actively growing weeds. Buckhorn plantain, Spray area overall; or to spot treat, low-volatile esters curly dock, dandelion. fasten piece of kitchen sponge to (1) per acre (liquid end of stick or broom handle, dip or granular). sponge into solution, spot treat broadleaf weeds by pressing moist sponge against crown of each plant; delay mowing 24-48 hours; fall treatments allow cool-season lawn grasses to take over space left by dead weeds. 2,4-D amine salts or Late fall ; repeat in late Knotweed, wild garlic, Follow directions on label; several low-volatile esters winter or early spring wild onion. successive fall and spring treatments (1-2) per acre plus each year. necessary for control. detergent. WEED CONTROL IN NONCROPLAND CONSTRUCTION AIDS other desirable plants usually provides sufficient Ditchbanks; fence rows, floodways, road and competition to reduce greatly the weed problem utility rights-of-way, and other uncultivated areas and increase the effectiveness and economy of should be designed, constructed, and managed in grazing, mowing, or selective herbicides used for a manner to enhance efficient vegetation control. vegetation control. Establishment of suitable Ditchbanks should be shaped to provide uniform stands of the desired competitive vegetation is crowns and slopes, and a roadway should be much easier on recently constructed ditchbanks or maintained on one bank or each bank for efficient road rights-of-way than on those already heavily and economic use of mowers, burners, and spraying infested with weeds. Frequently weed growth can machinery. Shaping ditches, grades, and back be eliminated by repeated burning or by spraying slopes along highways to avoid steep or irregular with a nonpersistent herbicide and then grass or contours provides similar advantages. Fencing other revegetation mixture can be successfully ditch rights-of-way and providing suitable live- established. stock guards in lieu of gates greatly facilitate Grazing by livestock, where practicable and livestock grazing for weed control on ditchbanks. safe, usually provides effective and often the most The livestock must be managed to avoid over- economical means of vegetation control on ditch- grazing. banks and floodways. Other than grazing by live- Using metal fenceposts and metal or concrete stock, only a few biological agents effectively structures in or along ditches and highways greatly control weeds on noncropland. Examples are facilitates the use of weed burners without damage insects that control Scotch broom, gorse, and to the posts and structures. Set corner posts and St. Johnswort in fence rows and other uncultivated utility line poles in concrete to eliminate brace areas. rods and wires, which are obstacles to weed-control Repeated mowing or burning with a butane, treatments. liquid propane, or petroleum burner tends to eliminate or reduce tall weed species and encour- CULTURAL, BIOLOGICAL, AND ages the dominance of more desirable low-growing MECHANICAL CONTROL vegetation. Mowing or burning must be repeated Seeding ditchbanks, fence rows, and rights-of- three to eight times each growing season to main- way to adapted species of low-growing grasses or tain effective control of undesirable plants. SUGGESTED GUIDE FOR WEED CONTROL 19619 55 CONTROL WITH HERBICIDES were used alone, and the total rate of the mixture is usually less than that of the major component Choice of Herbicides and Rates herbicide if used alone. The herbicides most In choosing an herbicide or a mixture of herbi- commonly used in mixtures are the sodium bo- cides and the rate of appHcation for weed control in rates, sodium chlorate, simazine, and the phenyl- a noncrop area, the user should consider several urea compounds. However, most of the other environmental and site characteristics. They in- herbicides suitable for weed control on noncrop clude (1) the dominant kind of vegetation pres- areas are available in one or several mixtures. ent—annuals, deep-rooted herbaceous perennials, Soil sterilization is expensive and is practical grasses, broadleaf weeds, mixed vegetation, or only where complete vegetation control is desir- woody plants; (2) the objective—total vegetation able and soil erosion is not an important factor. control (soil sterilization—bare soil), selective Such areas are around signposts, bridge abut- control of broadleaf weeds and tall coarse ments, trestles along highways and railroads, grasses from short competitive and soil-binding utility poles, and buildings, under guardrails and grasses, or control of tall woody plants; (3) the transformer cages, along pipelines, on tank farms, type and fertility of soil—medium loam, heavy near structures, above concrete linings along clay, or light sandy or gravelly loam with high or canals, and in parking lots and other nonculti- low organic matter content; and (4) the amount vated land where accessibility, visibility, fire pre- and distribution of precipitation. vention, and other considerations justify the Many herbicides that are effective on broad- expense. leaf weeds are not effective on weedy grasses and vice versa, but some herbicides are effective Use of Herbicides for Woody Plants in Non- on both types. Usually the herbicides that are cropland most soluble in water or oil and are applied in The control of undesirable woody plants with sprays give the most rapid kill of top growth. herbicides along ditchbanks, roadsides, and utility Herbicides that are less soluble in water usually lines or on flood plains and other noncrop areas remain in the soil longer and provide weed control differs from that on pastures and rangelands in during a longer time. The minimum amount of the following respects: (1) The noncrop areas of precipitation required to leach soil-applied chem- woody plants frequently are in narrow strips so icals into the soil around weed roots to make the that aerial spraying often is not possible or feasible. herbicide effective ranges from 2 to 5 inches. (2) These areas usually are adjacent to or near Persistence of an herbicide in soil tends to be crops or ornamentals that are sensitive to phenoxy- longer under conditions of low precipitation, fine type herbicides. (3) Much greater care must be or tight texture of soil, low organic content, non- used in spraying woody plants. Dormant basal submergence by water, and low micro-organism spray, frill, or stump treatments frequently must content of the soil. Higher rates of application be substituted for foliage sprays along irrigation are usually required on heavier soils and soils canals, reservoirs, lakes, and ponds to avoid con- high in organic matter and in regions of greater tamination of water with herbicides not registered precipitation. More frequent application of her- for use in water. (4) Noncrop areas generally are bicides may be required to maintain weed control closer to adequate supplies of water so that use of on lighter soils and in areas of greater precipitation. high-volume drenching sprays is more economical Generally, repeated annual applications of soil and feasible than on rangelands. (5) Rapid con- sterilant herbicides at relatively light rates are trol or elimination of undesirable woody plants m more effective and economical than less frequent noncrop areas frequently is more critical and applications at heavier rates, especially for control economically feasible than it is in rangeland. of annual and shallow-rooted perennial weeds and Consequently, higher rates of herbicides and more seedlings of deep-rooted perennial weeds. expensive application methods, such as drenching Few chemicals used alone w411 kill all species of foliage sprays, aerial spraying with a helicopter, plants under all climatic and soil conditions and basal sprays, and cut-surface treatments, are com- at rates that are economically feasible. Mixtures monly used on noncrop areas. of herbicides with different solubilities in water and different weed specificities are used much Special Precautions in Use of Herbicides in more commonly for complete vegetation control Noncropland in noncrop areas than are used for selective weed control on either cropland or noncrop areas. Mix- Despite the absence of food or feed crops and tures are being widely used for soil sterilization usually of desirable ornamental plants in noncrop where the soil is unproductive and remains bare areas, all general precautions for safe use of her- for varying lengths of time. Usually each herbi- bicides described on page 3 should be followed. cide component in a mixture is applied at a rate Do not allow livestock to graze ditchbanks, rights- lower than the rate that would be required if it of-way, or similar noncrop areas sprayed with 56 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE herbicides not registered for use on pastures and Suggested Uses of Herbicides in Noncropland do not feed hay harvested from such areas. Examples of herbicide treatments that have Avoid contamination of water to be used for been used successfully in noncropland are given irrigation in canals, ponds, or reservoirs by her- in table 13. These examples show the scope of bicides not registered for use in aquatic areas or on herbicide usage in noncropland. They are also irrigated crops. Apply such herbicides on banks guides for the use of herbicides under local condi- of irrigation and drainage canals, ponds, and res- tions. However, rate ranges rather than specific ervoirs only when there is no water in the canal. rates are given. Times of application are given Use only amine or low-volatile esters of 2,4-D, in general terms because local climate, soil com- silvex, or 2,4,5-T for spray applications in noncrop position, and slope of land, proximity to canals or areas that are near sensitive crops or other desir- ponds or desirable plants, and other site conditions able plants and prevent spray drift onto the affect the performance and persistence of herbi- desirable plants. Use of low spraying pressure cides and methods required for their safe use. and higher volumes of water or oil reduces the Spot treatments for control of perennial weeds should be used where possible, especially where danger of spray drift. Additional protection there is likelihood of contaminating water or in- against spray drift onto desirable plants is pro- juring nearby desirable plants. Specific details vided by using invert emulsions of ester formula- for the safe and effective local use of herbicides tions and of particulating or other thickening can be obtained from weed specialists in the State agents with water-soluble herbicides. agricultural experiment stations. TABLE 13.—Weed control in noncropland {ditchbanks^ fence rows,floodways, industrial sites, and railroad, highway, and utility line rights-of-way) ^ [Numbers in parentheses=pounds of active herbicide per acre] Weed and treatment Time of application Remarks BROADLEAF HERBACEOUS WEEDS (SELECTIVE CONTROL IN DESIRABLE GRASSES) Annuals, shallow-rooted perennials, and seedling perennials : Dicamba (0.5-1) Early weed growth in spring. Kills only top growth of most perennials. 2,4-D (1-2) Early growth to first bloom__ Repeat as necessary to maintain control during growing season. 2,4,5-T (1-2) do_ Use for weeds difficult to control with 2,4-D, e.g., nightshade. Deep-rooted and other hard-to-kill perennials : PBA (20-60) Spray succulent foliage growth, Some grasses injured by heavier rates. preferably during period of adequate rainfall. Picloram (2-3) _ Rapid vegetative growth to early Use special care to avoid spray drift on bloom in spring or summer, vigor- desirable plants or contamination of ous rosette growth in fall, or soil water to be used for irrigation; apply application in fall. only as thickened spray; picloram persists for 3 years in some soils. Picloram plus 2,4-D mixture (follow Rapid vegetative growth to early Do. instructions on label). bloom in spring or summer, vigor- ous rosette growth in fall. TBP (8-16) During early growth or in fall when Repeat as necessary to eliminate or ground is not frozen. reduce stand. 2,3,6-TBA (10-30) Spray succulent foliage growth, Some grasses injured by heavier rates. preferably during period of adequate rainfall. 2,4-D (2-4) Rapid vegetative growth to early Repeat as necessary to eliminate or bloom in spring or summer, vigor- reduce stand. ous rosette growth in fall. 2,4,5-T (2-4) do Use for weeds diflacult to control with 2,4-D, e.g., perennial horsenettle. See footnotes at end of table. SUGGESTED GUIDE FOR WEED CONTROL 19619 57 TABLE 13.—Weed control in noncropland (ditchbanks, fence rows, floodways, industrial sites, and railroad, highway, and utility line rights-of-way) ^—Continued Weed and treatment Time of application Remarks WEEDY GRASSES WHERE CONTROL OF BROADLEAF WEEDS NOT NECESSARY Annuals and seedling perennials : Aromatic oil, 40-80 gal. per acre Spray young growth Repeat as necessary to maintain control. Dalapon (5-10) Spray young growth 4-8 in. tall. Do. DNBP or PCP fortified fuel oil, Spray young growth Use 2-3 pt. DNBP or 2-3 qt. PCP 40-80 gal. per acre. per 100 gal. fuel oil. Established perennials (bermudagrass, Johnsongrass, paragrass, quack- grass, reed canarygrass) : Aromatic oil (120-160 gal. per acre) do Repeat every 3-4 weeks during growing season to eliminate or reduce stand. Dalapon 2 (10-15) Spray young growth 6-18 in. tall Repeat as necessary to suppress growth. Dalapon 2 (20-30) Early growth to early heading. _ _ Repeat every 6-8 weeks or as necessary to eliminate or reduce stand; lighter rates repeated more frequently sometimes more effective. DNBP fortified fuel oil, 120-160 gal. Spray young growth Same as with aromatic oil; use 2-3 per acre. pt. DNBP per 100 gal. fuel oil. DSMA or MSMA, 2.5-5 lb. per When weeds are actively growing. Add 1-2 pt. surfactant and spray 100 gal. water per acre. until thoroughly wet. Sodium TCA (100-150) On aftermath growth in fall or as More effective when adequate pre- soil treatment. cipitation follows ; may seed desira- ble grasses next season. Established perennials (Phragmites, reed canarygrass) : Amitrole (8-12) On young growth before heading. Repeat 2-3 times each growing season to eliminate or reduce stand; lighter rates will suppress growth; use only in drainage ditches and marshes. Amitrole-T (4-6) do_ Do. PERENNIAL SEDGES ON IRRIGATION AND DRAINAGE DITCHBANKS Tall sedges along irrigation and drain- age ditches, around ponds (e.g., Nebraska sedge) : Amitrole or amitrole-T (5-10) On young growth 10-15 in. tall Repeat 2-3 times each growing season to suppress growth; use only in . . . _, . drainage ditches and marshes. Amitrole or amitrole-T (10-20) On young growth before heading Repeat every 6-8 weeks as necessary to eliminate stand; use only in drainage ditches and marshes. Dalapon (15-30) On young growth 10-15 in. tall Repeat as necessary to suppress growth to desired extent; use only i^xTüT-» r j.'i2 j, r 1 ., -.^^ in drainage ditches and marshes. DNBP fortified fuel oil, 120-160 do Repeat every 4-6 weeks as necessary gal. per acre. to eliminate stand; use 2-3 pt. DNBP per 100 gal. fuel oil; avoid contamination of irrigation or potable water. 2,4-D (60-80) do_ Repeat as necessary to eliminate stand; permits survival and spread of Kentucky bluegrass; avoid con- tamination of irrigation or potable water. MIXED HERBACEOUS BROADLEAF AND GRASS WEEDS Annuals, biennials, shallow-rooted perennials, and seedling perennials (lower rates) ; estabhshed deep- rooted and other hard-to-kill perennials (higher rates) : See footnotes at end of table. 58 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 13.—Weed control in noncropland (ditchbanks, fence rows, floodways, industrial sites, and railroad, highway, and utility line rights-oj-way) ^—Continued Weed and treatment Time of application Remarks MIXED HERBACEOUS BROADLEAF AND GRASS WEEDS continued Amitrole or amitrole-T (3-5; 6-12)___ Early growth to first bloom Repeat as necessary to maintain con- trol or to eliminate or reduce stand; do not use along irrigation canals, reservoirs, lakes, ponds. Amitrole plus simazine mixture do Gives longer lasting control than (follow instructions on label). amitrole alone; do not use along irrigation canals, reservoirs, lakes, ponds. AMS (50-100; 400-1,000) do Mix 3^-2 lb. per gal. water and spray to wet foliage; 1 formulation regis- tered for use adjacent to reservoirs, lakes, ponds, canals, and streams including domestic water supplies at rates up to 200 lb. per acre. Aromatic oil, 40-80 and 120-160 Spray young growth Repeat as necessary to maintain con- gal, per acre. trol or every 3-4 weeks to eliminate or reduce stand. Borate (sodium), 30-120 lb. per Before period of adequate precipita- Apply broadcast as soil treatment. 1,000 sq. ft.; (1,300-5,200). tion. Borate mixtures with sodium Soil applications before period of Use where soil sterilization (bare soil) chlorate and/or other chemicals adequate precipitation; spray ap- desired. (follow instructions on label). plications on early growth to first bloom. Bromacil (3-6; 10-25). Early growth to first bloom or be- Apply higher rates before period of fore period of adequate precipita greatest precipitation or when tion. bottom or margins of canals, ditches, or ponds are not submerged by water. Chlorate (sodium) (300-600; 700- Spray foliage and make soil appli- Observe all precautions to avoid fire 1,300). cations before period of adequate hazard. precipitation. Chlorate mixtures with borates or do Fire hazard usually less but caution other chemicals (follow directions necessary. on label). Dalapon plus 2,4-D or 2,4,5-T or Early growth to early bloom or Use 2,4,5-T where broadleaf weeds silvex (5-10 plus 1-2; 15-30 plus heading. resistant to 2,4-D are present. 2-4). Dicamba (1-4; 4-8) When weeds in active growth stage- Higher rates equally effective as soil application before period of ade- quate precipitation. Diuron or monuron (5-20; 20-80) _ Before period of adequate precipita- Diuron gives longer soil sterility; tion. monuron more effective on deep- rooted weeds. DNBP or PCP fortified fuel oil, Young growth to first heading Repeat as necessary to maintain con- 40-80 and 120-160 gal. per acre. trol or every 3-4 weeks to eliminate or reduce stand; use 2-3 pt. DNBP or 2-3 qt. PCP per 100 gal. fuel oil. Erbon (120-160). When weeds are young and suc- Make soil applications in late fall or culent or during period of ade- winter in regions of wet winters and quate precipitation. dry summers. Ethylene glycol bis(trichloroacetate) Spray when weeds are about 12 in. Apply in fuel oil in sufficient volume (10-20). tall. to give complete coverage of all foliage. Monuron-TCA (20-40; 40-66) When weeds are young and suc- Make soil applications in late fall or culent or during period of ade- winter in regions of wet winters quate precipitation. and dry summers. Oil, 40-50 gal. per acre aromatic Young growth to first heading Apply same as for aromatic or forti- or fortified fuel oil, plus 2,4-D fied fuel oil; more economical and ester (2-3). often more effective than oil alone. Paraquat (cation) (0.5-2) Spray young growth Repeat as necessary to maintain con- trol ; kills top growth only of peren- nials. Prometone (10-15; 20-60). Spray early growth to first heading- Mix in water or oil; oil spray kills top growth quicker. See footnotes at end of table. SUGGESTED GUIDE FOR WEED CONTROL 19619 59 TABLE 13.—Weed control in noncropland {ditchbanks, fence rows^floodways, industrial sites, and railroad, highway, and utility line rights-qf-way) ^—Continued Weed and treatment Time of application Remarks MIXED HERBACEOUS BROADLEAF AND GRASS WEEDS Continued Simazine or atrazine (5-20; 20-40) _ __ Spray early growth to first heading; Simazine requires more precipitation soil applications before period of for effective root kill; remains ample precipitation. effective in soil longer. UNDESIRABLE WOODY PLANTS Alder, Baccharis, boxelder, cotton- At full leaf in spring or early Apply in 100-300 gal. water per acre wood, poplar, sycamore, willow, summer. with ground equipment, or in 5-10 and other species susceptible to gal. water per acre or oil-water or 2,4-D, 2,4,5-T (2-4). invert emulsion by airplane or helicopter. Mixed species including some sus- _do_ Do. ceptible to 2.4-D, 2,4-D plus 2,4,5-T (brush-killer mixture) (2-4) of 2:1 or 1:1 mixture. Species resistant to 2,4-D or in areas near crops susceptible to 2,4-D: AMS (7-10) in 2 gal. water Spray over freshly cut stump or in Cut notches every 6 in. around frills or notches cut around base circumference of tree; crystals may of tree. be sprinkled liberally over cut stumps or in frills or notches. AMS (60) in 100 gal. water At full leaf in spring or summer_ Spray to thoroughly wet foUage ; with airblast mist-spray equipment use 100-400 lb. per 100 gal. water and apply at lower volume; to apply in oil-water emulsion follow directions on label; use mist spray only in areas far removed from crops. Fenuron (east of Rocky Moun- Just before or during period of Apply broadcast or in grid pattern at tains) (12-25). adequate precipitation in spring 1-2 teaspoonfuls 3 ft. apart; apply from bud growth to full leaf. same rate around base of individual trees or clumps of brush for spot treatments; increase rate 50 percent for cherry, dogwood, elderberry, osageorange, persimmon, sassafras. Fenuron TCA (12-25) Spray at full leaf stage or broad- Available in liquid, granular, and cast before or during period of pelleted formulations for spray or adequate precipitation in spring. broadcast applications. Picloram (6-8.5) Broadcast granules just before or Highest rate is necessary for ash, during period of adequate blackgum, and oak ; for spot precipitation. treatments under individual trees or clumps of brush broadcast 1-2 tablespoonsful per 30 sq. ft. of soil surface; picloram persists for 3 years in some soils. Picloram plus 2,4-D mixture (follow Spray at full leaf during vigorous Use extreme care to avoid drift of instructions on label). growth. spray to nearby desirable plants; spray solution may be applied to cut stumps or in frills; apply only in thickened spray; picloram persists in some soils for 3 years. Silvex (2-4) Spray at full leaf during active Silvex especially effective on maple, growth; spring treatments best mulberry, palmetto, redbud, salt- for some species (e.g., saltcedar). cedar (Tamarix sp.), trumpetyine. 2,3,6-TBA (10-20) Spray foliage and soil when condi- Especially effective on woody vines. tions suitable for active growth. 2,4,5-T (2-4) Spray at full leaf during active Especially effective on brambles, growth; spring treatments best mesquite, oak, osageorange. for some species (e.g., saltcedar). 1 All herbicides listed are registered under the Federal 2 When stand of perennial grass or sedge weakens, Insecticide, Fungicide, and Rodenticide Act for suggested herbicide treatments are less frequent, and broadleaf uses at time of publication, but some herbicides registered weeds begin to invade, add amine or low-volatile ester for use may not be included. Rates are in terms of acid formulation of 2,4-D at 1 to 2 lb. per acre. equivalent or active ingredient of herbicide and not neces- sarily or usually of commercial formulation. 60 AGRICULTURE HANDBOOK 3 32, U.S. DEPT. OF AGRICULTURE CONTROL OF AQUATIC WEEDS CONSTRUCTION AIDS Flooding.—Maintain the water level at a depth of 3 feet or more for several months to control Deepening the edges of ponds, lakes, and cattails and certain other emersed weeds. reservoirs to 2 or more feet and filling in marshy Fertilization.—Frequent application of NPK spots prevent or reduce growth of emersed weeds (nitrogen, phosphorus, potassium) mineral fertil- such as cattail and waterprimrose. Also, fertilizers izers in ratios of 8-8-2, 10-10-5, or higher stimu- and herbicides control submersed weeds at the lates a dense growth or ''bloom'' of microscopic shoreline more effectively when the water is not algae, which shades the pond bottom and prevents shallow. Removal of stumps, logs, and other or reduces the growth of rooted submersed weeds obstructions from ponds, lake margins, and access in the Southern States. To control rooted sub- channels facilitates the use of underwater weed mersed weeds and waterlilies in ponds with stable mowers. water levels, apply 100 to 200 pounds per acre of A uniform gradient and absence of high or low NPK mineral fertilizer (analysis 8-8-2) beginning spots in the bottom of an irrigation canal permit in late winter or early spring and at 10-day inter- thorough draining of water and effective and vals thereafter until a white disk placed 12 to 14 economical control of submersed waterweeds in inches below the water surface is invisible. Sub- 3 or 4 days of drying. Deep canals with steep sequently apply fertilizer as necessary to maintain gradients and rapid waterflow provide less favor- the algae ''bloom.'' Fertilization does not control able conditions for growth of rooted submersed submersed weeds where the outflow or change of weeds. water in a month exceeds the water storage ca- Lining irrigation and drainage canals with con- pacity of the canal or pond or in cooler waters of crete or asphalt usually prevents or reduces the the Central and Northern States. growth of rooted submersed weeds. However, Livestock Grazing.—Intensive grazing by live- filamentous algae may grow on concrete linings stock, where practicable and safe, provides effec- and structures and greatly reduce waterflow ca- tive and economical control of most kinds of pacity. Also, silt deposits on the bottom of lined emersed and marsh species, including aquatic canals will support obstructive growth of rooted grasses, sedges, rushes, reeds, cattails, alligator- submersed weeds in water as deep as 8 or 10 feet. weed, watercress, and willows. Avoid grazing A few species will grow at depths of 25 or 30 feet. where it causes serious erosion of steep banks or Careful designing and spacing of checks, weirs, loose soil. Ducks often effectively control duckweed turnouts, bridges, and other structures along in small ponds. canals minimize interference with the operation of equipment for mechanical or chemical control of HAND AND MECHANICAL CONTROL aquatic weeds. Shaping ditchbanks to provide uniform crowns and slopes and maintaining road- Although the traditional hand and mechanical ways on one or both banks are essential for efficient methods of controlling aquatic weeds have re- chaining, dragging, mowing, or spraying operations cently been replaced to a considerable extent to control aquatic weeds. by herbicides, the hand and mechanical methods are still advantageous in many situations. MANAGEMENT PRACTICES Control of submersed weeds by mechanical methods often is less costly than chemical methods As supplements to proper design and construc- in canals with flows of water greater than 70 c.f.s. tion of canals, ponds, lakes, and reservoirs, a However, in canals that supply water for sprinkler number of management practices can be utilized irrigation, mechanical methods are undesirable to control aquatic weeds or prevent them from because fragments of dislodged weeds that remain becoming a problem. These practices include in the water often clog sprinkler heads, valves, draining, flooding, fertilization, and livestock screens, and other irrigation equipment. grazing. Hand Pulling.—^Young plants of cattail, button- Draining.—^For control of submersed weeds in bush, willow, and certain other emersed or marsh irrigation canals with uniform bottom gradients, species can be eliminated by hand pulling. How- drain completely and let canals dry for 3 or 4 days. ever, frequent inspection of the channel, pond, or Repeat as necessary when water is not critically needed for irrigating crops. marsh and pulling when plants are young and few To control cattails and certain other emersed in number are necessary for effective and economi- weeds in ponds, marshes, and wet lands, drain cal control. water off, plow the ground, and let it dry for a Underwater Mowing.—Self-propelled and boat- few weeks. mounted mowers that cut off submersed or SUGGESTED GUIDE FOR WEED CONTROL 19619 61 emersed weeds below the water surface at depths waterhyacinth in 1902 and submersed weeds in of 6 inches to 6 feet are available. 1927. However, most of the herbicides now To eliminate cattails, cut the stems off below registered by the U.S. Department of Agriculture the water surface during the early heading stage for use in controlling one or more aquatic weeds and again 1 to 2 months later when all regrowth were discovered since 1945. Herbicides often give is emersed. A third cutting is necessary when more effective, longer lasting, and less expensive regrowth occurs a second time. control of aquatic weeds than do mechanical or For killing small patches of waterlilies and hand methods. watershield, cut leaves off below the water surface at frequent intervals. Five or six cuttings a year may be necessary. For temporary control of submersed waterweeds Special Precautions in Use of Aquatic Herbicides in large canals, around boat docks, and in fishing A few aquatic herbicides are poisonous to hu- and swimming areas of ponds and lakes, mow off mans and warmblooded animals and must be as deeply as possible and remove dislodged weeds. handled and used with great care and according In canals the dislodged weeds should be trapped to special procedures. Some herbicides are toxic downstream and removed by dragline or other to fish, but several do not injure fish at concen- device to prevent them from lodging against trations required to kill weeds. Most aquatic structures, clogging the canal, and causing over- herbicides do not injure crops irrigated with water flows, canal breaks, or washed-out structures. at concentrations required for weed control, but In ponds and lakes weed debris accumulating in a few may injure crops at low concentrations. shallow water along the shoreline because of Only limited information is available on the wave action can be removed by draglining, persistence and fate of herbicides in water, aquatic cabling, conveying, or other mechanical means. soil, fish, aquatic plants, and crops irrigated with Chaining and Dragging.—For removal of sub- treated water. Therefore, in addition to following mersed waterweeds from irrigation or drainage all general precautions for the safe use of herbicides canals, pull a heavy chain, drag, or disk upstream described on page 3 and the special precautions along the bottom of the canal with a tractor on in table 14, the user of an aquatic herbicide each bank. Several trips are usually necessary to must follow carefully all label instructions and dislodge all weed growth. Trap the floating restrictions regarding aquatic situations in which masses of weeds at strategic places downstream the herbicide should not be used, including treated and remove mechanically or by hand. water for livestock, potable purposes, and irriga- tion of crops. He must know how much time should elapse after herbicide treatment and before BIOLOGICAL CONTROL treated water may be used for drinking, fishing, swimming, and irrigating crops. A few species of fish (e.g., Israeli carp, Tilapia) are the only organisms that can be recommended to control certain species of submersed weeds. Other organisms under study include certain Suggested Uses of Herbicides for Control of insects to control alligatorweed and waterhyacinth ; Aquatic Weeds a large fresh-water snail to control algae, sub- mersed weeds, waterfern, and possibly water- Examples of herbicide treatments that have hyacinth; and several low-growing submersed been used successfully and safely for control of species, such as waterplantain and dwarf sagittaria, aquatic weeds are given in table 14. These examples as effective competitors with ranker growing, more show the scope of herbicide usage for aquatic troublesome pondweeds in large irrigation canals. weed control. They are also guides for the use To control branched filamentous algae {Pitho- of herbicides under local conditions. However, phora) in southern ponds, stock with fifty 5-inch rate ranges rather than specific rates are given or larger fingerling Israeli carp per acre. Under and times of application are given in general these temperature conditions the Israeli carp will terms, because local climate, altitude, water not muddy the water and will not spawn success- temperature, water uses, and site conditions fully. affect the performance and persistence of herbi- cides and procedures required for effective and safe use. Specific details for the safe and effective CHEMICAL CONTROL local use of aquatic herbicides can be obtained from aquatic weed specialists of State and Federal Copper sulfate was first used to control algae in agencies familiar with the particular local 1904, and sodium arsenite was used to control situation. 62 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE TABLE 14.—Control of aquatic weeds (irrigation canals, drainage ditches, streams, lakes, ponds, reservoirs, marshes) Type and kind of aquatic Herbicide ^ Rate or Remarks weed or aquatic site concentration 2 FLOATING WEEDS (UNATTACHED, TOPS ABOVE WATER) AUigatorweed (floating mats), duckweed, waterfern (Salvinia), waterhyacinth, waterlettuce : General control (all 2,4-D amine salts or 2-4 lb. per 100 gal. Spray to uniformly wet foliage when weeds weeds). low-volatile esters. diluent. actively growing; include 10 gal. fuel oil and 1 pt. emulsifier for waxy hard-to-wet foliage or in rainy season; repeat every 4-6 weeks. Near crops sensitive to 2,4-D: Duckweed (nonflowing Diquat (cation)- 0.5-1 p.p.m.w ._ Inject into water or spray on foliage when water). actively growing; much less effective in muddy water. Waterhyacinth. Amitrole-T 1-1.5 lb. per acre. ._ Apply as surface spray in 150-200 gal. water or as aerial spray in 7.5 gal. water per acre when actively growing; add 0.1 lb. fenac per acre for more rapid foliage kill; use only in drainage ditches and marshes. Waterhyacinth and Diquat (cation). 1-1.5 lb. per acre. ._ Apply as surface spray in 150-200 gal. water waterlettuce. or as aerial spray in 7.5 gal. water per acre when actively growing. More positive eradica- Ester of silvex _ _ 8 lb. per acre____ . _ Apply as spray in 150-200 gal. water per acre tion—alligatorweed at ñrst bloom; re-treat when regrowth floating mats. 2-4 in. above water; 2-4 applications re- quired for control; do not use for irriga- tion or domestic purposes. EMERSED AND MARGINAL WEEDS (ROOTED UNDER WATER, TOPS ABOVE WATER, OR GROWING ON WET SOIL) Broadleaf species: General control Silvex, 2,4-D, or 2-4 lb. per acre_ Apply as spray in 200 gal. water per acre to 2,4,5-T. uniformly wet foliage when weeds actively growing; reduce volume but not rate when foliage wet; repeat as necessary. Arrowhead, lotus, 2,4-D (low-volatile 1-4 lb. per acre_ Apply in oil or in oil-water emulsion (1:10 pickerelweed, smart- ester). or 1:20) in sufficient volume to give weed, spatterdock, uniform coverage; spray when plants spikerush, water- actively growing. primrose, white waterlily, other plants with waxy leaves. Rooted, emersed alligator- Ester of silvex 8 lb. per acre. Apply as spray in 150-200 gal. water per weed. (spray). acre at ñrst bloom; re-treat when regrowth 2-4 inches above water; 2-4 applications required for elimination. Grass and grasslike species : Perennial grasses and /'Amitrole or 8-16 lb. per acre Apply in 100-400 gal. water per acre as sedges, e.g., common amitrole-T. ground spray or in 10-15 gal. water per reed (Phragmites), cut- acre as aerial spray when plants 6-18 in. grass, Johnsongrass, tall and before heading; some grasses, e.g., knotgrass, paragrass, reed canarygrass, require 50 percent less quackgrass, ripgut sedge. amitrole-T than amitrole; use only in drainage ditches and marshes. .Dalapon 20-30 lb. per acre Apply in 100-400 gal. water per acre as ground spray or in 5-15 gal. water per acre as aerial spray when grasses 6-18 in. tall and before heading; add 3-4 pt. wetting agent per 100 gal. water; repeated light applications at 5-10 lb. per acre are more effective on some species, e.g., paragrass; use only in drainage ditches and marshes. See footnotes at end of table. SUGGESTED GUIDE FOR WEED CONTROL 19619 63 TABLE 14.—Control oj aquatic weeds {irrigation canals, drainage ditches, streams, lakes, ponds, reservoirs, marshes)—Continued Type and kind of aquatic Herbicide ^ Rate or Remarks weed or aquatic site concentration ^ EMERSED AND MARGINAL WEEDS (ROOTED UNDER WATER, TOPS ABOVE WATER, OR GROWING ON WET SOIL) Continued Amitrole 6-12 lb. per acre. Apply at fully headed or postheading stage in late summer or early autumn in suffi- cient volume of spray to give uniform coverage by ground or aerial equipment; apply at earlier growth stage for control during current season and repeat as necessary to eradicate regrowth; use only Bulrushes and cattails in drainage ditches and marshes. Dalapon 15-30 lb. per acre. Same as for amitrole except include 3-4 pt. wetting agent or 5-10 gal. diesel oil plus 1 pt. emulsifier per 100 gal. spray. 2,4-D (low-volatile 4-6 lb. per acre- Apply in 1:20 oil-water emulsion at 150-300 esters) . gal. per acre; make initial application at first heading and repeat on regrowth before heading; 3-4 applications necessary for elimination. SUBMERSED WEEDS (TOPS MOSTLY UNDER WATER, USUALLY ROOTED OR ANCHORED) Ponds, lakes, and reser- voirs: 'Copper sulfate 0.1-0.5 p.p.m.w _ Apply crystals or powder at early stage of (pentahydrate, algae growth by any method to give rapid dark blue). and uniform dispersion; repeat as neces- Algae, blue-green- sary to maintain control; safe in potable water. Dichlone 0.02-0.05 p.p.m.w. _ Same as copper sulfate except not safe in potable water. 'Copper sulfate 0.5-1 p.p.m.w _ In soft water safe on most fish except trout; (pentahydrate, safe in potable water. Algae, filamentous. dark blue). 1-2 p.p.m.w _ In hard water injurious to most fish; safe in potable water. Endothall (dimeth- 0.05-0.2 p.p.m.w-_ _ Apply uniformly over surface or inject below ylamine salts). water surface. Endothall (dimeth- 0.5-2.5 p.p.m.w _ Use only for spot treatments or where some ylamine salts). fish kill is not objectionable. Rooted or anchored Endothall (disodium 1-4 p.p.m.w. _ _ Consult weed specialists in State agricultural weeds, e.g., bladder- salt). experiment stations or extension service wort, cabomba, coon- or fish and wildlife specialists for necessary tail, Elodea, naiad, use permit and regulations ; apply at early pondweeds, water- stage of weed growth; use lower concen- chestnut, water crow- trations in total area treatments and foot, watermilfoil, higher concentrations for margins, spot water pennywort, treatments, or cold water; follow label waterprimrose, water- directions on use of treated water; increase stargrass, wild celery. concentration to 5 p.p.m.w. for spot treat- ments. Fenac 15-20 lb. per acre- _ Apply to temporarily exposed lake or pond bottoms and shorelines when soil is not frozen; keep water down at least 3 weeks; follow label directions on use of treated water. '7-10 lb. per acre. - Apply to temporarily exposed lake or pond bottoms and shorelines; follow label direc- tions on use of treated water. Same weeds plus algae Dichlobenil , 10-15 lb. per acre. _ Broadcast over water surface before or as and chara. soon as new growth begins in spring; in- crease rates in water deeper than 3 ft. and for spot treatment. See footnotes at end of table. 64 AGRICULTURE HANDBOOK 3 3,2, U.S. DEPT. OF AGRICULTURE TABLE 14.—Control of aquatic weeds (irrigation canals, drainage ditches, streams, lakes, ponds, reservoirs, marshes)—Continued Type and kind of aquatic Herbicide ^ Rate or Remarks weed or aquatic site concentration 2 SUBMERSED WEEDS (TOPS MOSTLY UNDER WATER, USUALLY ROOTED OR ANCHORED) Continued '0.25-0.5 p.p.m.w- Low concentrations sufficient for some weeds, e.g., naiad in small ponds. Same weeds except Diquat (cation). 0.5-1.5 p.p.m.w-- Apply over surface or inject below water Elodea and wild surface; double rates for spot treatments; celery. follow label directions on use of treated water. Ester of 2,4-D 20-40 lb. per acre, Apply uniformly over water surface by boat (granule or pellet or helicopter at early stage of weed growth; Same weeds except form). use heavy rates for more resistant species curlyleaf pondweed, or extremely acid or alkaline water; esters some other pond- of 2,4-D toxic to some species of fish at weeds, Elodea, wild these rates. celery. Potassium salt of 1.5-2 p.p.m.w. or 5 Apply uniformly oyer surface of water or silvex (granule or lb. per acre-ft. inject liquid below surface at early stage liquid form). of weed growth; not effective in spot treatments. 1-2.5 gal. per c.f.s_ Inject into canal at beginning of weed infes- tation during 3^-4 hours using especially adapted equipment; effective kill 6-20 miles downstream depending on weed Irrigation and drainage density. canals with flowing Acrolein. 0.1-0.6 p.p.m.v- Inject in large canals (200-2,000 or more water—most submersed c.f.s.) at one location during period of species except water- 8-48 hours; within this range use lower plantain. concentrations and longer periods of ap- plication as size of canal increases; apply from special cylinders under nitrogen gas pressure. Aromatic solvents 8-10 gal. per c.f.s. Add 1-1.5 percent emulsifier and inject into (xylene). (600-740 p.p.m.v. canal at one station during 30-60 minutes in 30 minutes or before weeds become matted at surface; 300-370 p.p.m.v. add 4-5 gal. per c.f.s. to moving ''zone" of in 60 minutes). treated water at intervals of 2-4 miles down canal depending on weed density; avoid fire hazard. ^Acrolein. 4-7 p.p.m.v Apply below water surface continuously along canal with specially adapted equip- ment; toxic to fish. Drainage and irrigation Diquat (cation). 0.25-1 p.p.m.w Apply above or below water surface con- canals with flow stopped < tinuously along canal; allow at least 12 or greatly reduced. hours' exposure of weeds to treated water. Endothall (di- 1.5-4 p.p.m.w Same as diquat except toxic to fish. methylamine salt). Reservoirs and large canals carrying flowing water for potable use: Continuous feed method__- Copper sulfate 0.6-1 p.p.m.W- Begin applications early in season at 1 (pentahydrate). p.p.m.w.; gradually reduce to 0.6 p.p.m.w. in late summer as water temperature rises. Repeated ^^slug" treat- -do___L 0.3-2 lb. per c.f.i Make initial application early in growing ments. season and repeat as necessary to main- tain control; use light rates for soft water and heavier rates for water high in salts, especially carbonates; apply large crystals on concrete bottom or apron or suspend in water in burlap bags; crystals dissolve very slowly. 1 All herbicides listed are registered under Federal 2 Rates and concentrations are in terms of acid equiva- Insecticide, Fungicide, and Rodenticide Act for suggested lent or active ingredient of herbicide and not necessarily uses at time of publication, but some herbicides registered or usually of commercial formulation. for use in control of aquatic weeds may not be included. SUGGESTED GUIDE FOR WEED CONTROL 19 619 65 APPENDIX HERBICIDE TOLERANCES FOR CROPS Crop and herbicide P.p.m. Diuron: Croy and herbicide P.p.m. Forage 2. 0 Alfalfa: Grain 1. 0 Diuron 2. 0 Linuron, ears or grain .25 Simazine 15. 0 Propachlor, forage 1.5 Apples : Corn, sweet: AMS 5.0 Atrazine : Dalapon 3. 0 Fodder or forage 15. 0 Dichlobenil . 15 Grain (cobs, with husks removed, and Diuron 1. 0 kernels) .25 Terbacil . 1 Dalapon: 2,4-D (acid or oil-soluble amine) 5. 0 Dry ears (cobs and kernels) and grain 5. 0 Apricots, dalapon__ 1. 0 Fodder and forage 5. 0 Artichokes, diuron 1. 0 Linuron: Asparagus : Ears or grain .25 Dalapon 30. 0 Fodder or forage 1. 0 Monuron 7. 0 Propachlor: Sesone 2. 0 Forage 1. 5 2,4-D (sodiura salt) 5. 0 Grain (cobs, with husks removed, and Avocados: kernels) . 1 Dichlobenil . 15 Cotton: Monuron 1. 0 Dalapon, cottonseed 35. 0 Bananas, diuron . 1 DCPA, cottonseed . 2 Barley, 2,4-D: Diuron, cottonseed 1. 0 Forage 20. 0 Linuron, cottonseed . 25 Grain . 5 Monuron, cottonseed 1. 0 Beans, lima, trifluralin .05 Prometryne : Beans, snap: Cottonseed .25 DCPA 2.0 Forage 1. 0 Trifluralin . 05 Trifluralin, cottonseed .05 Bermudagrass, sprigged : Cranberries : Diuron, grass and hay . 7 Dalapon 5. 0 Simazine 15. 0 Dichlobenil . 15 Blackberries, diuron 1. 0 Eggplant, DCPA \. 0 Blueberries, diuron 1. 0 Flax, dalapon, seed 75. 0 Boysenberries, diuron 1. 0 Garlic, DCPA L 0 Broccoli : Gooseberries, diuron 1. 0 DCPA 1.0 Grapes : FW-925 . 75 Dalapon 3. 0 Trifluralin . 05 Diuron 1. 0 Brussels sprouts: Grasses, diuron, seed ñelds 2. 0 DCPA 1.0 Kale, DCPA 2.0 Trifluralin . 05 Lettuce: Cabbage: Benefin .05 DCPA 1.0 DCPA, head and leaf 2. 0 FW-925 . 75 Loganberries, diuron 1.0 Cantaloup, DCPA 1. 0 Macadamia nuts, diuron .1 Carrots, linuron 1. 0 Mangoes, dichlobenil . 15 Mint, diuron, hay 2.0 Cauliflower : Mustard greens, DCPA 5.0 DCPA 1.0 Oats, 2,4-D: FW-925 J . 75 Forage 20.0 Trifluralin . 05 Grain .5 Cherries, dichlobenil . 15 Okra, trifluralin .05 Citrus (grapefruit, lemons, oranges) : Olives, diuron 1.0 Bromacil, grapefruit, lemons, oranges . 1 Onions: Dalapon, grapefruit, limes, oranges, tan- DCPA 1.0 gerines 5. 0 Monuron, dry bulbs 1.0 Dichlobenil . 15 Parsnips, with or without tops, linuron .5 Diuron : Peaches: Pulp 4. 0 Dalapon 15. 0 Whole fruit 1. 0 Dichlobenil . 15 Terbacil . 1 Terbacil . 1 Collards, DCPA 2. 0 Peanuts : Corn: Benefin .05 Atrazine : Sesone J6. 0 Fodder and forage 15. 0 Vernolate, forage and hay .1 Grain (cobs with husks removed, and Pears : kernels) .25 AMS 5.0 Dalapon: Dalapon 3.0 Dry ears (cobs and kernels) and grain 10. 0 Diuron 1. 0 Fodder and forage 5. 0 2,4-D (acid or oil-soluble amine) 5. 0 66 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE Crop and herbicide P.p.m. Crop and herbicide P.p.m. Peas, dalapon, forage and peas 15.0 Linuron, dry and succulent forage and hay 1. 0 Peas, southern: Nitralin . 1 DCPA 2.0 Trifluralin . 05 Trifluralin .05 Squash, summer and winter, DCPA 1.0 Peppermint: Strawberries : Diuron, hay 2. 0 Chloroxuron . 1 Terbacil, hay .1 DCPA 2. 0 Peppers: Diphenamid 1. 0 DCPA 2.0 Sesone 2. 0 Trifluralin . 05 Pineapples : Sugar beets: Bromacil . 1 Dalapon, roots and tops 5. 0 Diuron 1. 0 Pebulate, roots and tops . 1 Monuron 1.0 Sugarcane: Plums: Diuron 1. 0 Dalapon 1. 0 Monuron 1. 0 Dichlobenil . 15 Terbacil . 1 Potatoes : Sweetpotatoes, DCPA 2. 0 Dalapon 10. 0 DCPA 2.0 Tomatoes : Linuron 1. 0 DCPA 1. 0 Sesone ^ 6. 0 Pebulate . 1 Raspberries, diuron 1. 0 Trifluralin . 05 Rice, molinate, grain and straw .1 Trefoil, birdsfoot, diuron. forage and hay 2. 0 Sorghum: Turnip greens, DCPA 5. 0 Atrazine: Turnips, DCPA, roots 2. 0 Fodder and forage 15. 0 Walnuts, English, diuron . 1 Grain . 25 Propachlor: Wheat: Forage 3. 0 Diuron: Grain . 25 Forage, hay, straw 2. 0 Soybeans : Grain - 1. 0 Chloroxuron : 2,4-D: Dry . 15 Forage 20. 0 Hay . 15 Grain • 5 SUGGESTED GUIDE FOR WEED CONTROL 19619 67 CROP INDEX FIELD, FRUIT, AND VEGETABLE CROPS Page Mustard greens 39, 65 Page Oats "33, 34^65 Alfalfa 27,34,48,49, 65 Okra 39,65 Almonds 41 Olives 41,43,65 Apples 40, 65 Onions 39^65 Apricots 41, 65 Oranges 42,43,65 Artichokes 37, 65 Orchardgrass 29, 34, 52 Asparagus 38,' 65 Parsley 39 Avocados 42, 65 Parsnips _ 39,65 Bananas 42,' 65 Peaches 41, 65 Barley 22, 33, 34^ 65 Peanuts "'/_ 22,'65 Beans: Pears 41, 65 Lima 37, 65 Peas 39,65 Pole 37 Peas, southern 39, 65 Snap 37, 65 Peppermint 39, 65 Beets 37 Peppers 39,46,65 Bentgrass- 34 Pineapples 42, 43, 65 Bermudagrass 45 Plums 41,65 Blackberries 44, 65 Potatoes 39, 65 Blueberries 44, 65 Pumpkins 40 Bluegrass 34 Radish 40 Boysenberries 44, 65 Raspberries 44, 65 Broccoli 37, 65 Rice iö, 30-33,65 Brussels sprouts 37' 65 Ryegrass 29,34 Cabbage 38, 65 Saflflower 22, 30 Cantaloup 38, 65 Sorghum 22, 23, 30, 36,' 65 Caraway 38 Soybeans 10, 15, 23-25, 30, 36 Carrots 10, 11,38,65 Spinach 40 Cauliflower 38, 65 Squash 40, 65 Celery 38', 46 Strawberries 43, 44, 65 Cherries 41, 65 Sugar beets 25, 35^ 65 Chicory 38 Sugarcane 26, 65 Clover : Sweetpotatoes 36, 40, 65 Alsike 28, 34, 49, 50 Tangerines 65 Crimson 28, 34,49, 50 Tobacco ii, 18,26,40,65 Ladino 28, 34, 49, 50 Tomatoes 12, 18, 46 Red 28,34,49,50 Trefoil 28,34,49,65 Subterranean 28, 34, 49, 50 Trefoil, birdsfoot 48 Sweet 28, 49, 50 Turnip greens 40, 65 White 28, 34, 49, 50 Turnips 40, 65 Collards-- 38, 65 Walnuts, English 41,65 Corn 11, 18, 19, 35, 65 Watermelons 40 Corn, sweet 11, 18, 19, 38, 65 Wheat 33,34,65 Cotton 10, 15, 18-20, 30, 65 Wheat, durum 33, 34 Cranberries 43, 44, 65 Wheat, hard red spring 33, 34 Cress, upland 38 Cucumbers 38 Dates 42 ORNAMENTALS AND SHADE TREES Dill 38 Page Eggplant 38,46,65 Ageratum 45 Endive 38 Almond, flowering 46 Escarole 38 Alyssum 45 Fescue, creeping red 34 Amur corktree 46 Fescue, tall 34 Arborvitae 45, 46 Flax 29,65 Ash 46 Garhc 38, 65 Aster 45 Gooseberries 44, 65 Astilbe 45 Grapefruit 42, 43, 65 Azalea 45, 46 Grapes 12, 18, 43, 44, 65 Babysbreath 45 Grasses 50,65 Balsam 45, 46 Hanover salad 38 Barberry 45, 46 Kale 38, 65 Bayberry 46 Legumes 28, 33, 48, 49, 51 Beautybush 46 Lemons 42, 43, 65 Birch 45,46 Lentils 38 Birch, white 45, 46 Lespedeza 28, 34, 51 Bleedingheart 45 Lettuce 39, 65 Bluebell 45 Limes 43, 65 Boxelder ^ 46 Loganberries 44, 65 Boxwood 45, 46 Macadamia nuts 42, 43, 65 Bush-honeysuckle 45, 46 Mangoes 43,65 Camellia 45,46 Mint 39, 65 Caragana ^ 46 68 AGRICULTURE HANDBOOK 3 3 2, U.S. DEPT. OF AGRICULTURE Page Page Carnation 45 Maple 45,46 Cedar 46 Marguerite, golden 45 Cedar, eastern red 45, 46 Marigold 46 Chamaecyparis 46 Mockorange 45, 46 Chrysanthemum 45 Moss rose 45 Cleyera japónica 46 Mountain-ash 46 Coleus 45 Mourning bride 45 Columbine 45 Nandina 46 Coneflower, purple 45 Narcissus 45, 46 Coralbell 45 Oak 46 Cotoneaster 46 Oak, red 46 Cottonwood 46 Osmanthus (hoUyolive) 46 Crabapple 46 Pachistima 46 Cypress, Elwood 46 Pachy sandra 45 Daffodil 46 Peony 45 Dahlia 45,46 Periwinkle 45 Delphinium.--: 45 Petunia 45, 46 Deutzia 46 Photinia 46 Dianthus 45 Picea 46 Dogwood 46 Pine 46 Douglas-fir 46 Pine, Austrian 46 Elm 46 Pine, mugo 46 Elm, American 46 Pine, red 46 Elm, Chinese 46 Pine, Scotch 46 Elm, Siberian 46 Pine, white 46 Euonymus 45, 46 Pinks, mourning 45 Evening-primrose 45 Pittosporum 46 Feverfew 45 Plum 46 Fir, Fraser 46 Podocarpus 46 Firethorn 46 Pokerplant 45 Forget-me-not 45 Poplar 45, 46 Forsythia 45,46 Potentilla 45 Fuchsia 45 Privet 45,46 Gardenia 46 Privet, variegated 45 Gladiolus 45,46 Pyracantha 46 Golden-rain-tree 46 Quince, flowering 46 Hackberry 46 Redcedar 46 Heather 46 Rhododendron 45, 46 Hemlock - - 46 Rockrose 46 Holly 46 Rose 45, 46 Honeylocust 46 Rose, multiflora 45, 46 Honeysuckle 45, 46 Russian-olive 46 Hydrangea 45, 46 Sage, scarlet 45 Iris__-__ 45,46 Salvia 45 Iris, Dutch 45,46 Snapdragon 45 Ivy 46 Spirea 45,46 Ivy, English 45 Spruce 4 46 Juniper 45, 46 Spruce, blue I 46 Juniper, creeping 45, 46 Spruce, Norway -. 46 Kinnikinnick 46 Spruce, red i 46 Lantana 45 Spruce, white I 46 Larkspur, candle 45 Squawcarpet 46 Laurel 45, 46 Tulip 45,46 Leucothoe 46 Verbena 45 Lilac 45,46 Viburnum 45,46 Lily 45,46 Weigela 46 Linden 46 White-cedar 46 Locust 46 Willow 46 Lupine 45 Wintercreeper 45 Magnolia 45,46 Yew - 45,46 Mahonia 45, 46 Zinnia 45 SUGGESTED GUIDE FOR WEED CONTROL 19619 69 WEED INDEX Page Page Agarita {Mahonia trifoliolata (Moric.) Fedde) 52 Cockle, cow (Saponaria vaccaria L.) 34 Alder (Alnus spp.) 57 Cocklebur (Xanthium spp.) 7, 21, 24 Algae: Coffeebean. (See Sesbania.) Blue-green (many genera) 5, 30, 61, 63 Coontail (Ceratophyllum spp.) 63 Filamentous green (many genera) 5, 30, 60, 61, 63 Cottonwood (Populus spp.) 52, 57 Pithophora spp 5^ 30 Crabgrass (Digitaria spp.) 1, 5, 7, 9-11, 48, 52 Alligatorweed (Alternanthera philoxeroides (Mart.) Crabgrass, hairy (Digitaria villosa (Walt.) Pers.) _ 4, Griseb.) 2, 60-62 5, 7, 9, 1Ö, 48, 52 Arrowhead (Sagittaria spp.) 31, 62 Crabgrass, smooth (Digitaria ischaemum (Schreb.) Ash (Frazinus spp.) 52, 59 Muhl.) 1,5,7,9-11,48 Ash, white {Fraxinus americana L.) 5, 52, 59 Cress, hoary (Cardaria draba (L.) Desv.) 5, 34, 35 Aster, woody (Aster parry i A. Gray) 51 Crowfoot, water (Ranunculus spp.) 63 Baccharis (Baccharis spp.) 52, 57 Cutgrass (Leersia spp.) 62 Barley, wild (Hordeum leporinum Link) 22, 33, 65 Daisy (Chrysanthemum spp.) 6 Barnyardgrass (Echinochloa crusgalli (L.) Beauv.)__ 5, Dallisgrass (Paspalum dilatatum Poir.) 9, 53 7, 10, 30-32 Dandelion (Taraxacum officinale Weber) 51, 54 Bayberry (Myrica pensylvanica Loisel.) 52 Deathcamas (Zigadenus spp.) 48, 51 Beakrush (Rhynchospora spp.) 30 Dock, curlv (Rumex crispus L.) 5, 10, 47, 51, 54 Bedstraw {Galium spp.) 51 Dodder (Cuscuta spp.) 49 Bedstraw, smooth (Galium mollugo L.) 35, 51 Dogbane (Apocynum spp.) 35 Beech (Fagus grandifolia Ehrh.) 52 Dogfennel (Eupatorium capillifolium (Lam.) Small) _ 7, Bermudagrass (Cynodon dactylon (L.) Pers.) 5, 26,34 8, 10, 50, 52, 57 Dogwood (Cornus spp.) 59 Bindweed (Convolvulus spp.) 8, 10, 12 Ducksalad (Heteranthera limosa (Sw.) Willd.) 30-33 Bindweed, field (Convolvulus arvensis L.)___ 7, 8, 10, 12, 35 Duckweed (Lemna spp.) 62 Birch (Betula spp.) 52 Elbowbush (Forestiera pubescens Nutt.) 52 Bitterweed (ß'eienmm awarwm (Raf.) Rock) 49 Elderberry (Sambucus spp.) 59 Blackgum (Nyssa sylvatica Marsh.) 52, 59 Elm ( Ulmus spp.) 52 Bladderwort ( Utricularia spp.) 63 Elodea (Elodea spp.) 63, 64 Bluegrass (Poa spp.) 29, 53 Fescue, red (Festuca rubra L.) 10, 29, 34 Bluegrass, Kentucky (Poa pratensis L.) 10, 53, 57 Fescue, tall (Festuca spp.) 53 Boxelder (Acer negundo L.) 57 Fimbristylis (Fimbristylis spp.) 31,32 Brackenfern (Pteridium spp.) 7 Flatsedge (Cyperus spp.) 30-33 Bramble (Rubus sp.) 59 Foxtail, giant (Setaria faberii Herrm.) 7, 10, 25 Brome, downy (Promus tectorum L.) 10, 51 Foxtail, green (Setaria viridis (L.) Beauv.) 7, 10, 25 Brome, Scotch (Cytisus scoparius (L.) Link) 2, 54 Foxtail, yellow (Setaria glauca (L.) Beauv.) 7, 10, 25 Bromegrass (Promus spp.) 49 Garlic, wild (Allium vineale L.) 10, 12, 48, 51, 54 Bromegrass, downy (Bri/mus tectorum L.) 49 Goldenrod (Solidago spp.) 6 Broomsedge (Andropogon virginicus L.) 50 GoosQgvSiss (Eleusine indica (IJ.) Gaertn.) 53 Broomweed, common (Gutierrezia dracunculoides Gooseweed (Sphenoclea zeylanica Gaertn.) 31-33 (DC.) Blake) 51 Gorse ( JJlex europaeus L.) 2, 54 Buckbrush (Symphoricarpos spp.) 48,51 Groundcherry (Physalis spp.) 26 Buckwheat, wild (Polygonum convolvulus L.) 25, 34 Hackberry (Celtis spp.) 52 Bulrush (Scirpus spp.) 5, 30, 63 Halogeton (Halogeton glomeratus (M. Bieb.) C. A. Burclover (Medicago polymorpha var. vulgaris Mey.) 2,51 (Benth.) (Shinners) 53 Haw, red (Crataegus spp.) 52 Burdock (Arctium spp.) 1, 51 Henbit (Lamium amplexicaule L.) 10, 26, 49-51, 53, 54 Burhead (Echinodorus cordifolius (L.) Griseb.) 31 Hickory (Carya spp.) 52 Buttonbush (Cephalanthus occidentalis L.) 60 Honeylocust (Gleditsia triacanthos L.) 52 Cabomba (Cahomba caroliniana Gray) 63 Horehound (Marrubium vulgäre L.) 51 Cactus, cholla (Opuntia spp.) 2, 52 Horsenettle (Solanum carolinense L.) 56 Canary grass, reed (Phalaris arundinacea L.) 5, 57, 62 Horsetail rush (Equisetum spp.) 5 Cane, wild (Sorghum bicolor (L.) Moench) 19 Huisache (Acacia farnesiana (L.) Willd.) 52 Carpetweed (Mollugo verticillata L.) 7 Hydrangea (Hydrangea spp.) 52 Carrot, wild (Daucus carota L.) 1 Indigo, curly (Aeschynomene virginica (L.) BSP.)_- 30-32 Catclaw (Schrankia nuttallii (DC.) Standl.) 52 Ironweed (Vernonia spp.) 51 Cattail (Typha spp.) 1, 5, 7, 30, 60-62 Ivy, ground (Glechoma hederacea L.) 53 Ceanothus (Ceanothus spp.) 52 Ivy, poison (Rhus radicans L.) 5, 34, 40 Celery, wild (Apium leptophyllum (Pers.) F. Muell.)_ 63, Johnsongrass (Sorghum halepense (L.) Pers.) 1, 64 7-9, 11, 20, 21, 24, 26, 35, 50, 57, 62 Chara (Chara spp.) 63 Joint vetch, northern (curly indigo) (Aeschynomene Cheat (Promus secalinus L.) 1 indica L.) 30-32 Cherry (Prunus spp.) 59 Knapweed, Russian (Centaurea repens L.) 5, 7, 35 Chestnut (Castanea spp.) 52 Knawel (Scleranthus annuus L.) 51 Chickweed (Stellaria media (L.) Cyrillo) 6-8, Knotgrass (Paspalum distichum L.) 30, 62 10, 26, 28, 47-52 Knotweed (Polygonum spp.) 7, 50, 53, 54 Chicory (Cichorium intybus L.) 51 Koa haole (Leucaena leucocephala (Lam.) de Wit.)_- 26 Chinaberry, wild (Melia azedarach L.) 52 Lambsquarters (Chenopodium spp.) 5, 7, 10, 49 Chinkapin (Castanea spp.) 52 Larkspur, low (Delphinium nelsonii Greene) 51 Clover (Trifolium spp.) 53, 54 Larkspur, tall (Delphinium barbeyi Huth) 52 Clover, white (Trifolium repens L.) 53 Lettuce, wild (Lactuca spp.) 26 Cockle, corn (Agrostemma githago L.) 7, 34 Locoweed (Astragalus spp.) 51 70 AGRICULTURE HANDBOOK 332, U.S. DEPT. OF AGRICULTURE Page Page Lotus, American (Nelumbo lutea (Willd.) Pers.) 62 Redstem {Anmania auriculata Willd.) 31-33 Lupine, silvery (Lupinus argenteus Pursh) 51 Reed, common {Phragmites communis Trin.) 62 Madrone {Arbutus menziessi Pursh) 52 Reeds {Phragmites spp.) 60 Manzanita (Arct staphylos spp.) 52 Retama {Parkinsonia aculeata L.) 52 Maple (Acer spp.) 52, 59 Rice, red {Oryza sativa L.) 30 Maple, red {Acer ruhrum L.) 52, 59 Rocket, yellow {Barbarea vulgaris R. Br.) 33, 49, 50 Maple, silver {Acer saccharinum L.) 52, 59 Rushes {Juncus spp.)_-_ 35, 60 Mescalbean {Sophora secundiflora (Ort.) Lag.) 52 Sagebrush, big {Artemisia tridentata Nutt.) 48, 51 Mesquite {Prosopis spp.) 48, 59 Sagebrush, low {Artemisia arbuscula Nutt.) 48, 51 Mesquite, honey {Prosopis glandulosa var. glandu- Sagebrush, sand {Artemisia filifolia Torr.) _' 48, 51 /osa (Torr.) Cockerell) 48,52,59 Sagittaria, dwarf {Sagittaria subíala (L.) Buchenau)- 61 Mesquite, velvet {Prosopis velutina (Woot.)) 48, 52 Saltcedar (Tamarix pentandra Pall.) 59 Mexicanweed {Caperonia castaneaefolia (L.) St. Sandbur {Cenchrus spp.) 53 Hil.) 30,31 Sassafras (Sassafras spp.) 52,59 Milkvetch, timberline {Astragalus sp.) 51, 52 Sedge, Nebraska {Carex nebraskensis Dewey) 30, Milkvetch, twogrooved {Astragalus bisulcatus 32, 60, 62 (Hook.) Gray) 51 Sedge, ripgut {Carex lacustris Willd.) 30, 32, 60, 62 Morningglory {Ipomoea spp.) 7, 8, 26 Sedges {Carex spp.) 30, 32, 60, 62 Mulberry {Morus spp.) 52, 59 Sesbania, hemp {Sesbania exáltala (Raf.) Cory)_ 25, 30-33 Mullein {Verbascum spp.) 1 Shepherdspurse {Capsella bursa-pastoris (L.) Mustard {Brassica spp.) 12, 33, 34, 49 Medic.) 1 Mustard, tumble {Sisymbrium altissimum L.) 12, Signalgrass, broadleaf {Brachiaria platyphylla 33, 34, 49 (Griseb.) Nash) 30,32 Naiad {Najas spp.) 63, 64 Smartweed {Polygonum spp.) 2, 5, 7, 31, 34, 62 Nightshade {Solarium spp.) 26 Sneezeweed {Helenium spp.) - 49, 51 Nimblewill {Muhlenbergia schreberi J. F. Gmel.) 53 Sneezeweed, orange (western) {Helenium hoopesii Nutsedge {Cyperus spp.) 1, 7, 20, 21, 24, 36, 49 Gray) 49,51 Nutsedge, purple {Cyperus rotundus L.) .7, Sorrel, red {Rumex acetosella L.) 7, 53, 54 20, 21, 24, 36, 49 Sowthistle {Sonchus spp.) 35 Nutsedge, yellow {Cyperus esculentus L.) 7, Spatterdock {Nuphar advena (Ait.) Ait. f.) 62 20, 21, 24, 36, 49 Spicebush {Lindera benzoin (L.) Blume) 52 Oak {Quercus spp.) : 48 Spikerush {Eleocharis spp.) 30-33, 62 Oak, blackjack {Quercus marilandica Muenchh.) 52, 59 Spirea, narrowleaf {Spiraea alba Du Roi) 52 Oak, bur {Quercus macrocarpa Michx.) 48, 52, 59 Sprangletop {Leptochloa spp.) 30, 32 Oak, pin {Quercus palustris Muenchh.) 48, 52, 59 Spurge, leafy {Euphorbia esula L.) 5, 34, 35 Oak, poison {Rhus toxicodendron L.) 5, 48, 59 St. Johnswort {Hypericum perforatum L.) 2, 54 Oak, post {Quercus stellata Wangenb.) 48, 52, 59 Strawberry, wild {Fragaria spp.) 7 Oak, red {Quercus rubra L.) 48, 59 Sumac {Rhus spp.) 52 Oak, shinnery {Quercus havardii Rydb.) 48, 51, 59 Sweetgum (Liquidambar styraciflua L.) 52 Oak, water {Quercus nigra L.) 48, 52, 59 Sycamore {Platanus spp.) 52, 57 Oak, white {Quercus alba L.) 48, 52, 59 Tansymustard {Descurainia pinnata (Walt.) Britt.)_ 51 Oak, willow {Quercus phellos L.) 48, 52, 59 Tarweed {Madia spp.) 49, 51 Oats, wild {Avena fatua L.) 5, Tasajillo {Opuntia leptocaulis DC.) 52 7, 11, 22, 25, 29,33,34, 59 Thistle, Canada {Cirsium arvense (L.) Scop.) 1, Onion, wild {A Ilium canadense L.) 51, 54 5, 7, 9, 34, 35, 50, 51 Orchardgrass {Dactylis glomerata L.) 29, 34, 52 Thistle, Russian {Salsola kali L. var. tenuifolia Osageorange {Madura pomifera (Raf.) Schneid.) __ 52, 59 Tausch) 8,51 Palmetto {Serenoa repens (Bartr.) Small) 59 Timothy (Phleum pratense L.) 52 Paragrass {Panicum purpurascens Raddi) 57, 62 Toadflax, Dalmatian {Linaria dalmática Mill.) 51 Pecan {Carya spp.) 52 Tree-of-heaven {Ailanthus altissima (Mill.) Swingle). 52 Pennycress {Thlaspi spp.) 1 Trumpetvine {Campsis radicans (L.) Seem.) 59 Pennywort {Hydrocotyle spp.) 53 Tules {Scirpus spp.). {See Bulrush.) Pennywort, water {Hydrocotyle umbellata L.) 53, 63 Velvetleaf {Abutilón theophrasti Medic.) 7 Pepperweed (Lepidium spp.) 49 Violet {Viola spp.) 53 Persimmon {Diospyros spp.) 59 Walnut {Juglans spp.) 52 Phragmites (Phragmites communis Trin.) 7 Waterchestnut ( Trapa natans L.) 63 Pickerelweed {Pontederia cordata L.) 62 Watercress {Nasturtium officinale R. Br.) 60 Pigweed {Amaranthus spp.)___ 1, 5, 7, 10, 12, 20, 26, 49, 51 Waterfern {Salvinia spp.) 61, 62 Plantain, buckhorn {Plantago lanceolata L.) 54 Waterhemlock {Cicuta spp.) 51 Pondweed {Potamogetón spp.) 61, 63 Waterhyacinth {Eichhornia crassipes (Mart.) Pondweed, curlyleaf {Potamogetón crispus L.)__ 61, 63, 64 Solms.) 2,5,31,61,62 Poplar {Populus spp.) 57 Waterhyssop {Bacopa caroliniana (Walt.) Robins.)- 31-33 Pricklyash {Zanthoxylum americanum Mill.) 5, 52 Waterlettuce {Pistia stratiotes L.) 62 Pricklypear {Opuntia spp.) 52 Waterlily {Nymphaea spp.) 61 Princesplume {Polygonum orientale L.) 51 Waterlily, white {Nymphaea tuberosa Paine) 62 Puncture vine {Tribulus terrestris L.) 2, 8 Watermilfoil {Myriophyllum spp.) 63 Purslane {Portulaca olerácea L.) 7, 20, 53 Waterplantain {Alisma spp.) 31, 61, 64 Quackgrass {Agropyron repens CL.). Beauv.) 5, Waterprimrose {Jussiaea spp.) 31, 60, 62, 63 7-12, 18, 35, 50, 52, 57, 62 Watershield {Brasenia schreberi Gmel.) 61 Rabbitbrush {Chrysothamnus spp.) 51 Waterstargrass {Heteranthera dubia (Jacq.) MacM.) _ 63 Ragweed, bur {Franseria discolor Nutt.) 1, Wildrye {Elymus spp.) 5 5, 35, 48, 49, 51 Willow {Salix spp.) 52,57,60 Ragweed, common {Ambrosia artemisiifolia L.)__ 5, 49, 51 Woodsorrel {Oxalis spp.) 53 Ragwort, tansy {Senecio jacobaea L.) 2, 51 Yerba-de-tago {Eclipta alba (L.) Hassk.) 31 Redbud {Cercis spp.) 59 Yucca {Yucca spp.) 51 U.S.GOVERNMENT PRINTING OFFICE : 1969—O-320-446