Guide to chemical weed control in crops discusses stages of growth in field crops and calculating the amount of chemical to apply per acre. Included are safety precautions

Derscheid, Lyle A.

Frost, Kenneth R.

Warner, Lloyd C.

English

Guide to chemical weed control in crops in 1964 discusses stages of growth in field crops, amount of chemicals for weeds, calculating the amount of chemical to apply per acre, and safety precautions

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Chemical Weed Control in Crops 1964

South Dakota State University Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange SDSU Extension Fact Sheets SDSU Extension 1963 Chemical Weed Control in Crops Kenneth R. Frost Lyle A. Derscheid Lloyd C. Warner Follow this and additional works at: https://openprairie.sdstate.edu/extension_fact Recommended Citation Frost, Kenneth R.; Derscheid, Lyle A.; and Warner, Lloyd C., "Chemical Weed Control in Crops" (1963). SDSU Extension Fact Sheets. 1242. https://openprairie.sdstate.edu/extension_fact/1242 This Fact Sheet is brought to you for free and open access by the SDSU Extension at Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. It has been accepted for inclusion in SDSU Extension Fact Sheets by an authorized administrator of Open PRAIRIE: Open Public Research Access Institutional Repository and Information Exchange. For more information, please contact michael.biondo@sdstate.edu. Historic, archived doculllent Do not assume content reflects current scientific knowledge, policies, or practices. SDSU ® Extension For current policies and practices, contact SDSU Extension Website: extension.sdstate.edu Phone: Email: 605-688-4 792 sdsu.extension@sdstate.edu SDSU Extension is an equal opportunity provider and employer in accordance with the nondiscrimination policies of South Dakota State University, the South Dakota Board of Regents and the United States Department of Agriculture. Chemical Weed Control Clean seed, proper seedbed preparation, good rota-tions, and sound soil management practices are prime requisites for controlling weeds in crops. They will eliminate many annual weeds and prevent infestation by most perennial weeds. Herbicides are valuable supplements to these practices. However, if we rely solely on chemicals and neglett standard practices, re-sistant weeds would increase. Once weeds become established, special practices are needed to eliminate them. These practices include the use of special cultivation, competitive crops, and herbicides in addition to the practices already men-tioned. One application of any one method seldom eliminates all perennial weeds. Even thc,ugh the weeds may be eliminated, a new infestation can become established from dormant weed seed in the soil. Some of these seeds remain viable for as long as 20 years and many years of diligent work are required to erad-icate them. Numerous tillage and chemical methods that will control weeds in crops are available. In fact, it is possible to eliminate some of the most persistent perennial noxious weeds while growing crops if the proper combination of crops, cultivation, and herbi-cides is used. For detailed information, see publications that dis-cuss control and elimination of specific noxious weeds or wild oats, pre-emergence weed control in crops, and chemical weed control in trees. By Kenneth R. Frost Jr., Extension Weed Specialist Lyle A. Derscheid, Professor of Agronomy Lloyd C. Warner, Assistant Professor of Agronomy Stages of Growth m Field Crops This plant is in the 5-leaf stage of growth. A plant with 4 leaves and 1 tiller. Also in 5-leaf stage. ~ l -· ID n :::, ft) n a.. :r ID r ... n 3 8~~~ r ~ ;,.; C 0 0 -· i· ~ m o -i -0 :::, n " ~ :I DI m en rt- -... r 0 -When using chemicals for weed control in crops (small grain especially), it is important to do it at the earliest possible time. This is important for two rea-sons: ( 1) the weeds are easier to kill when young and (2) the weeds are competing with the crop for mois-ture and nutrients. If competition is not removed early, weeds will cause yield reductions in the crop. This quite often happens by the time weeds are 6 inches tall. In experimental work weed-free wheat yielded 45 bushels per acre. Wheat infested with mustard sprayed at the 4-leaf stage yielded 43.5 bushels per acre, sprayed at the 6-leaf stage yielded 39.8 bushels per acre, sprayed at the early boot stage yielded 17.l bushels per acre, the same as unsprayed wheat. A plant with 3 leaves and 2 tillers is in the 5-leaf stage. Here's a close-up of the late boot stage. In the early boot stage of development, the stem is swollen between the second and third joint. "II Cit __, UI UI AMOUNT OF CHEMICAL FOR WEEDS The quantity of herbicide required for control varies with the weed species. The same amount of herbicide is less effective as the weed matures. The amount of 2,4-D or MCPA required to control numerous weeds at clif-f erent stages of growth is listed below. ¼ lb./A. Kochia, 2-4 in. Marsh elder, 2-4 in. Ragweeds, 2-4 in. Pennycress, 4-6 in. Pigweeds, 2-4 in. Mustard, 4-6 in. Lambsquarters, 4-6 in. ½ lb./A. Kochia, 4-8 in. Marsh elder, over 4 in. Ragweeds, over 4 in. Pennycress, over 6 in. Pigweeds, over 4 in. Mustard, over 6 in. Lambsquarters, over 6 in. Cocklebur, 2-6 in. Sowthistle, annual, 2-6 in. Sunflower, 2-6 in. Lady's thumb, 2-6 in. Velvet leaf, 4-6 in. Wild lettuce, 4-6 in. Russian thistle, 2-4 in. Wild buckwheat, 2 leaves Morning glory, annual Peppergrass, annual ½ lb./A. Kochia, over 8 in. Cinquefoil Gumweed, 6-12 in. Mare's tail Puncture vine Plantains Cocklebur, over 6 in. Sowthistle, annual, over 6 in. Sunflower, over 6 in. Lady's thumb, over 6 in. Velvet leaf, over 6 in. Wild lettuce, over 6 in. Russian thistle, 4-6 in. ¾ lb./A. Canada thistle Dandelion Field bindweed Perennial sowthistle 1 lb./ A. or more Bur ragweed Blue lettuce Buckbrush Goldenrod Hoary cress Leafy spurge Russian knapweed Sage brush Sagewort Toadflax CONTROLLING WEEDS IN CROPS Listed below is the maximum pounds of 2,4-D and MCPA acid equivalent that can be tolerated by crops without serious injury to the crop under most conditions. Use only enough to control the weed. Do not exceed the recommended rate. Also listed below are the rates of Dalapon, TCA, DATC, Barban, Atrazine, Amiben, and CDAA in pounds of acid equivalent or active ingredient required for each acre of area treated to control the weed under the specified conditions. In band applications the actual area treated will be treated at the same rate as an over-all (broadcast) treatment, but the over-all acreage will have less total chemical applied. Trade or brand names are listed in parenthesis after the chemical name. Trade names for 2,4-D, MCPA, and similar chemicals are too numerous to list here. Crop Weeds Safest time to spray Chemical Rate Remarks (Most tolerant growth lbs./A. stages of crop) Oat Varieties Lamb's quarters 3-leaf to dough 2,4-D ester ½ Mo-0-205 Marsh elder 2,4-D or MCP A ¾ Garry Annual morning amine* glory after dought 2,4-D 1 Dupree Mustards 5-leaf to dough 2,4-D ester ½ Puncture vine Minhafer Ragweed 2,4-D or MCPA ½ Burnett Cinquefoil amine* Cocklebur after dought 2,4-D 1 Ransom Wild lettuce 6-leaf to dough 2,4-D ester ½ These varieties may be injured by Waubay Pennycress 2,4-D or MCPA ½ treatment at 6-leaf to dough stage Newton Peppergrass amine* but weed control should more Andrew False flax after dought 2,4-D 1 than offset yield reductions. Annual vetch Brunker Annual sow 6-leaf to early boot 2,4-D ester ½ Clinton thistle 2,4-D or MCPA ½ Bonda Mare's tail amine* Ajax Pigweed after dought 2,4-D 1 Nemaha Lady's thumb after boot begins to swell 2,4-D ester ½ Cherokee Sunflower 2,4-D or MCP A ½ Velvet leaf amine* after dought 2,4-D 1 Mindo after heading 2,4-D ½ Marion after dought 2,4-D 1 2 u CONTROLLING WEEDS IN CROPS-(Continued) Safest time to spray (Most tolerant growth Rate Crop Weeds stages of crop) Chemical lbs./ A . Remarks . Spring wheat Same as for oats 5-leaf to early boot 2,4-D ester ½ and barley 2,4-D amine ¾ after dought 2,4-D 1 Wild oats 2-leaf stage, not more Barban ½-¾ Use 50-60 lb. pressure than 14 days after (Carbyne) weed emergence Durum wheat Wild oats Pre-emergence DATC (Avadex) 1¼ Apply to a smooth surface and and barley DATC-BW . incorporate into soil no deeper only (Avadex BW) than 2 inches immediately after treatment. DATC-BW formula-tion tends to be somewhat less in-)UflOUS to small grains than DATC Winter wheat Same as for oats Spring, fully stooled 2,4-D ester ½ Do not spray in fall and rye to boot 2,4-D amine ½ after dought 2,4-D 1 Flax Same as for oats Before weeds become 2,4-D or MCP A ~~ 2,4-D may delay maturity from 4 inches tall amine* 3-7 days Broadleaved After bolls turn 2,4-D ½-1 Germination of seed may be re-brownt duced if chemical is applied be-fore boll turns brown Foxtails Before weeds are 2 Dalapon ¾ Barnyard grass inches tall TCA 5 Wild oats Same as for wheat Barban ¼-½ Use 50-60 lbs. pressure and barley (Carbyne) Pre-emergence DATC (Avadex) 1½ Same as for durum wheat and DATC-BW barley (Avadex BW) Corn Same as for oats Before silking after 2,4-D ester ¼-½ Stalks often become brittle and several days of cool 2,4-D amine ½-¾ may suffer damage due to break-weather age After tasselingt 2,4-D 1 Use high-clearance sprayer with drop nozzles Foxtails Pre-emergence Atrazine 2-3 Must have ½ -1 inch of rainfall Barnyard grass within 2 ½ to 3 weeks after ap-Lam bsq uarters plication. Band application will Russian thistles reduce cost. Carryover will dam-age small grain but will not damage corn seeded next year CDAA-T 4 Must have ½ inch of rainfall (Randox T) within the first week after appli-cation. For several reasons gran-ulars maybe preferred over sprays here. Band applications will re-duce cost. Very irritating to skin and eyes, wear protective clothing Sorghum Same as for oats 4-12 inches tall 2,4-D ester ½ Heights are determined by meas-2,4-D amine ½ uring from ground to where a new leaf is emerging After headingt 2,4-D 1 Use high-clearance sprayer with drop nozzles CONTROLLING WEEDS IN CROPS-(Continued} Safest time to spray ' (Most tolerant growth Rate Crop Weeds stages of crop) Chemical lbs./A. Remarks Foxtails Pre-emergence CDAA (Ranclox) 4 As for corn Barnyard grass Soybeans Numerous Pre-emergence Amiben 3 Must have ½-1 inch of rainfall broadleaved after treatment but before weeds and grassy emerge. Band application will re-annuals duce cost CDAA (Randox) 4 As for corn Sugar beets Numerous Just before beets TCA 6 Must have rain or sprinkler irri-broadleaved emerge gation soon after application and grassy annuals Foxtails Postemergence Dalapon 2 Barnyard grass Before weeds are (Dowpon) 2 inches tall Postemergence Dalapon 4 Beets may be temporarily retard-After weeds are 3 (Dowpon) ed and yield may be reduced inches tall Wild oats Same as for spring Barban ¾ Use 50-60 lbs. pressure wheat and barley (Carbyne) Pre-emergence DA. TC (Avadex) 1½ Same as for durum wheat and barley Birdsfoot Lambsquartcrs Seedlings when com- 2,4-D arnine ¼ trefoil Mustards pan10n crop or weed MCPA amine* Alfalfa Ragweeds canopy lS 10-15" tall Red clover Pigweeds or established stands Alsike clover Marsh elder right after mowing Kochia When legume is over 2 4(2:t-DB) am111e ½ -1 Do not graze or harvest for feed Russian thistle inches tall ½-¾ 4(2,4-DB) ester for at least 30 days after treat-Lam bsq uarters ment. Do not use over ¾ lb. on Pigweed red clover. Higher rates will kill Mustards tops of Canada thistles and bind-weed Pennycress 4(2,4-DB) amine 1-1 ½ Same as above Smartweeds Ragweeds 4(2,4-DB) ester ¾-1 Alfalfa Foxtails Seedlings alone or in Dalapon 1-2 Forage from treated crops should Sweet clover Barnyard grass flax, established stand (Dowpon) not be fed to livestock. Do not Birdsfoot ( not wild oats) after mowing TCA 5 use high rate of Jalapon in flax trefoil Grasses Broadleaved Seedlings 2,4-DB ~~ -1 Don't graze or harvest for feed after 4-leaf stage for at least 30 days after applica-tion 2,4-D ¾ Chemical residue may appear in MCPA milk if dairy cows graze within 5 days after spraying. Palatibility of poisonous plants may be in-creased and injure livestock. Keep livestock off treated area for 7 to 10 days CONTROLLING WEEDS IN CROPS-{Continued) Safest time to spray (Most tolerant growth Rate Crop Weeds stages of crop) Chemical lbs./A. Remarks Broadleaved Established stands any 2,4-D ¾-2 time ( except heading MCPA time for seed fields), best 2,4,5-T weed control in June •MCPA is not so apt to injure the crop; however, it is less effective as a weed killer. Use only if mustards or lambsquarters are predominant weed species. tTreatment at this stage will not remove weed competition early enough to improve crop yield; however it may prevent weed seed production and will facilitate harvesting operations for small grain or flax. The most desirable growth stages for spraying both crops and weeds are relatively short. At this time the weeds are not easily seen; therefore, it is necessary to make a close inspection to determine the extent of the weed problem as well as the growth stage of the crop. CALCULATING THE AMOUNT OF CHEMICAL TO APPLY PER ACRE When applying chemicals in spray or granular form, it is essential to know exactly how much chem-ical is applied per acre. With sprays, it is also essential to mix water and chemicals in the right proportions. If this is not done, there is danger of injuring the crop with too much chemical or getting poor weed control with too little chemical. Therefore, the sprayer or granular applicator must be calibrated carefully and the chemical must be measured carefully for sprays. The calculations are the same for band applica-tions as for over-all (broadcast) treatments. SPRAYER CALIBRATION (Over-all or Band) Step 1. Select an an area for a test run that is similar to the field to be treated. Accurately measure a dis-tance of one-eighth mile or 660 feet. Step 2. Place the sprayer on level ground and fill the tank with water. Mark the water level in the tank. Step 3. Spray the test run, using the same gear and throttle setting on the tractor that will be used when spraying-usually 3 to 5 miles per hour. Also use the same spray pressure that will be used when spraying -somewhere between 30 and 50 pounds. Step 4. Return the sprayer to the original filling position, on level ground, and measure the amount of water required to refill the tank to the mark. Step 5. Multiply "66" times the amount of water required to fill the sprayer. Divide this answer by the width (feet) of the spray swath. This may be the width of swath from a regular field sprayer or may be total of several bands ( 4 x 14" ===56" or 4½ ') or ( 6 x 7"===42" or 3½'). This gives the number of gallons applied per acre. Step 6. Determine the number of acres that can be sprayed with one tankful of spray. Divide the number of gallons in the tank by the number of gallons ap-plied per acre. Measurement of Chemical for Sprays Step 7. Determine the amount of chemical needed per acre by checking in the fact sheet to see how much chemical is needed to kill the weed in question and also check to see if the crop will tolerate this amount. Step 8. Use table 1 to determine the number of quarts or pints of liquid required to spray an acre, or use table 2 to determine the pounds of dry ma-terial needed to spray an acre. Step 9. Calculate the number of pints or pounds needed in the sprayer. Multiply the acres that can be sprayed with one tankful of spray by the number of pints or pounds required per acre. GRANULAR APPLICATOR CALIBRATION Step 1. Use table 2 to determine the number of pounds of granular material required to give the number of pounds of active ingredient desired. For example, 20 pounds of atrazine granules containing 10% active ingredient contain 2 pounds of atrazine. Step 2. Consult applicators manufacturer's rate chart to determine the approximate setting required for the number of pounds of granules to be applied (20 pounds in step 1). Ad just setting on each hopper. Step 3. Select an area for a test run that is simi-lar to the field to be treated. Accurately measure a distance of one-eighth mile or 660 feet. Step 4. Fill hoppers and attach a container ( sack, pail, etc.) to each hopper for catching granules sep-arately from each hopper. Step 5. Put machine in gear and drive the test run, driving at the same speed that will be used when ap-plying the chemical. Step 6. Multiply "66" times the number of pounds collected from each hopper separately. Divide each answer by the total width (feet) treated by each hop-per (2 x 14"===28" or 2½' feet for 2-row bands). This gives the pounds of granular material applied per acre. If this is not the desired amount (20 pounds in step 1), readjust machine and repeat entire proced-ure until desired amount is obtained. Table 1. Conversion of Pounds to Pints or Quarts for Liquid Formulations Your chemical contains this much acid equivalent or active ingredient per gallon If you wish to apply this 1.00 2.00 2.64 or 2.68 3.00 3.34 or 3.40 4.00 many pounds per acre Apply this amount on each acre ½ 1 pt. ½ pt. ¾ pt. ½ pt. 3/10 pt. ¼ pt. ¼ 1 qt. 1 pt. ¾ pt. ½ pt. ½ pt. ½ pt. ½ 1½ qt. 1½ pt. lpt. 8/9 pt. 7 /9 pt. ½ pt. ½ -------------------- 2 qt. 1 qt. ¾ qt. ½ qt. 1½ pt. 1 pt. ¾ 3 qt. 1½ qt. 11/7 qt. 1 qt. 9 /10 qt. 1½ pt. 1 1 gal. 2 qt. 1½ qt. 1½ qt. 1½ qt. 1 qt. 1½ ------------------- ____ 1 ½ gal. 3 qt. 2¼ qt. 2 qt. 1½ qt. 1½ qt. 2 ------------------------------------------ 2 gal. 1 gal. 3qt. 2½ qt. 2½ qt. 2 qt. SAFETY FIRST Use care in following the directions listed above or on the manufacturer's label. The use of herbicides is recommended only when the chemicals are regis-tered by the U.S. Food and Drug Administration as to tolerances for application on crops raised for human food and livestock feed. Read the label first-not af-terward. The following are several rules of safety for those applying herbicides and other agricultural chemicals: Rule 1. Read the label before using the chemical. Observe directions and cautions to keep residue with-in the limits permitted by law. Rule 2. Avoid inhaling sprays or powders when mixing and applying herbicides. When directed on the label, wear a face mask or respirator. Rule 3. Do not spill sprays or powders on skin when mixing and applying herbicides. Wear gloves and goggles and other items of protective clothing whenever possible or if directed to do so. Rule 4. Wash hands and face and change to clean clothing after applying herbicides. Wash such cloth-ing before reuse. Rule 5. If symptoms of illness occur during or shortly after applying herbicides call a physician or get the patient to a hospital immediately. Rule 6. Dispose of empty herbicide containers. Store herbicides in original containers out of reach of children, pets, and irresponsible people. 6.00 ¼ pt. ½ pt. 4/9 pt. ½ pt. 1 pt. 1½ pt. 2 pt. 2½ pt. Table 2. Conversion of Pounds Active Ingredient to Pounds of Product for Powders and Granules Your chemical contains this percentage of acid equivalent or active ingredient If you wish to apply this many pounds per acre 4% 1 ---------------------------------- 25 lb. 2 -------------------------------------------------- 50 lb. 3 ---- 7516. 4 ______________________ 100 lb. 5 __________ ______ 125 lb. *85% sodium salt of dalapon. t90% sodium salt of TCA. 8% 10% 11.7% 20% 75% * 80% t 12½ lb. 2516. 37½ lb. 50 lb. 62½ lb. Apply this amount on each acre treated 10 lb. 8½ lb. 5 20 lb. 1716. 10 30 lb. 25½ lb. 15 40 lb. 34 lb. 20 50 lb. 42½ lb. 25 1 ~/2 lb. 2½ lb. 416. 5½ lb. 6½ lb. 1¼ lb. 2½ lb. 3¾ lb. 516. 6¼ lb. Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the Cooperative Extension Service of the South Dakota State College of Agriculture and Mechanic Arts, Brookings, John T. Stone, Director, U. S. Department of Agriculture cooperating. 7.SM-3-63-File: 15.141-Replaces F.S. 44 and 115-11182 ~"' 

Chemical Weed Control in Crops

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Chemical Weed Control in Crops

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