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Ferrell, J.A.
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"Revised November 2007. Reviewed November 2010."
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SS-AGR-06 Weed Management in Sorghum 1J.A. Ferrell, G.E. MacDonald, and B. J. Brecke2 1. This document is SS-AGR-06, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised November 2007. Reviewed November 2010. Please visit the EDIS website at 2. J .A. Ferrell, associate professor, Agronomy Department; G.E. MacDonald, professor, Agronomy Department, and B. J. Brecke, professor, Agronomy Department, West Florida Research and Education Center--Milton, FL; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611. The use of trade names in this publication is solely for the purpose of providing specic information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. Use herbicides safely. Read and follow directions on the manufacturers label. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or aliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim DeanSorghum has the ability to tolerate short-term drought and a late summer sorghum crop may follow an early-season corn crop. Weed control in sorghum is essential if high yields and ecient harvest are to be achieved; however, good weed control in sorghum is oen dicult to achieve. Sorghum is a small seeded grass and is relatively slow growing in the rst few weeks aer emergence. In addition, sorghum will not tolerate many of the herbicides which can be eectively used on corn. e slow seedling growth combined with the limited number of herbicides and low rates which must be used, creates a problem in sorghum weed control. Another problem is that many of the herbicides normally used on sorghum either cannot be used or must be used at low rates due to the coarse texture of many Florida soils. For these reasons it is essential that practices such as choice of hybrid, soil fertility, soil pH, moisture, and row spacing be optimized in an eort to give sorghum the best possible growing conditions to be as competitive as possible with weeds. e most important consideration is control of grasses during emergence and seedling development of the sorghum. If grasses are not controlled at this stage and are as large as the sorghum, then cultivation will not control the grasses in the drill without killing the sorghum. Sorghum should not be planted in elds that are heavily infested with johnsongrass. If grasses can be controlled until the sorghum gets an initial height dierential, cultivation can then be eective. If such a height dierential is achieved, post-directed sprays can also be eective. Broadleaf weeds are a less serious problem since several materials can be eectively used for their control. Table 2 should be used to determine which herbicides are most eective for the weeds anticipated or present in your situation. en use Table 1 to determine rates and application recommendations. Proper calibration and application are essential since rates too low will result in poor control and rates too high may result in crop injury.


2 Table 1. Weed management in sorghum. Trade Name and Rate of Commercial Product Per Acre Common Name and Rate of Active Ingredient Per Acre Remarks PREEMERGENCE Dual II Magnum or Dual Magnum 1.0 1.33 pt S-metolachlor Use on seed that has been treated with a chemical safener such as Concep. If seed is not properly treated, severe injury will occur. Good control of many grasses and certain small seeded broadleaf weeds. Apply after planting before weeds and sorghum emerge. It can also be applied with uid fertilizer.2Stalwart, Parallel, others 1 to 1.3 pt metolachlor See above. Note that metolachlor products will commonly provide less soil residual control than those containing S-metolachlor. Outlook, Sortie 13 oz dimethenamid Similar to S-metolachlor. Less eective on tropical spiderwort. POSTEMERGENCE AAtrex or Atrazine3(several formulations) atrazine 1 to 2 lb ai/A Apply after sorghum reaches the 3-leaf stage and before broadleaf weeds are 4 tall. For ground applications add emulsiable oil concentrate at 1 qt/A. Do not apply more than 2 lb per application and do not apply more than 2.5 lb/A/season. Do not graze or feed forage for 21 days following application. A restricted use pesticide. Aim EC 0.5 1 oz carfentrazone Can be applied to sorghum from 30 days prior to planting to the 6 leaf collar growth stage. Controls many broadleaf weeds, but good coverage is essential. Addition of non-ionic surfactant (0.25% v/v) is required, but crop oil is not recommended due to increased crop injury. Directed applications are recommended if rates higher than 0.5 oz will be used. Expect moderate leaf burning from over-the-top applications. Do not apply to sweet sorghum. 2,4-D amine4(several brands) 2/3 to 1 pt of 4 lb/gal 2,4-D Broadleaf weeds controlled. Sorghum is not as tolerant to 2,4-D as corn. Broadcast after sorghum is 6-8 tall. If sorghum is 10-15, use drop nozzles to direct spray toward base of plant. Over the top applications are most likely to result in herbicide injury. Do not treat sorghum in boot, tassel, or soft dough stage. Avoid drift. Banvel, Clarity, Sterling 40.5 pt dicamba Broadleaf weeds controlled. Apply from the 3 leaf stage until plant reaches 8 tall. Plants that are between 8 and 15, apply only as a directed spray. Do not graze or feed treated sorghum, forage, or silage prior to mature grain stage. Avoid drift. Basagran 1.5 2.0 pt bentazon Apply overtop before weeds exceed 4-6 inches in height. Grain sorghum should be fully emerged. Sorghum is very tolerant to bentazon, but do not apply to sorghum that is heading or blooming. Apply with a crop oil adjuvant at a rate of 1 qt/A. Buctril 2EC 1 1.5 pt bromoxynil Apply to sorghum between the 3 leaf stage to 12 height or pre-boot stage to control most broadleaf weeds in 2-4 leaf stage of growth. Use 10 or more gallons of water per acre. Lorox 4L 1 2 pt linuron Apply as a directed spray after sorghum is 12 tall. Use low rate when sorghum is 12 to 15 tall, and a sprayer equipped with skids, shoes or shields. Use the high rate when sorghum is 15 tall and weeds are up to 4 in height. Make only one application per season. Add nonionic surfactant (1pt./25 gals. spray). DO NOT graze or feed plant parts to livestock within 3 months after application. Gramoxone Inteon 1 2 pt paraquat Controls grass and broadleaf. Apply as a directed spray when sorghum is a minimum of 12 tall and weeds are less than 3 tall. Do not spray higher than 3 on sorghum plant. Add nonionic surfactant at 1 qt per 100 gal of spray.


3 Trade Name and Rate of Commercial Product Per Acre Common Name and Rate of Active Ingredient Per Acre Remarks Peak 57DF prosulfuron Provides postemergence and residual controls of many annual broadleaf weeds. Apply after sorghum reaches 5 inches in height and before 30 inches. Refer to label for specic weed sizes but as a general rule apply before weeds reach greater than 4-6 inches high. The use of a non-ionic surfactant or crop oil is recommended. May be tank-mixed with Banvel, 2,4-D, or atrazine. Do not apply Peak within 15 days to sorghum treated with foliarly applied organophosphate insecticides. Do not graze within 30 days, or harvest silage within 40 days, of application. Do not apply to sweet sorghum. Rotational restrictions include the following: wheat, barley, rye, oats 0 months; eld corn 1 month; peanuts, tobacco, cotton 10 months. Sandea 2/3 1 oz halosulfuron May be applied from the 2 leaf stage through layby (before head emergence) to control nutsedge and other broadleaf weeds. Do not apply more than 1 oz/A/yr. Applications to a stressed crop will increase injury for 7-10 days. Prowl 3.3 EC 1.2 1.8 pt or Prowl H20 1.5 pt (culti-spray) pendimethalin For extended control of late-season grasses, cultivate so that brace roots and stems are covered and protected when sorghum is 4 in height or in the 2-leaf stage. Immediately spray with Prowl. If rainfall (0.5) is not received within 7 days after application, incorporate with a sweep-type or rolling cultivator. Can be tank-mixed with atrazine.1 Concep III, manufactured by Syngenta Corp., is a seed protectant which is applied to sorghum seed to minimize injury when the herbicides Dual Magnum or Dual II Magnum are used on sorghum for weed control. Screen, manufactured by Monsanto Company, is a seed protectant which is applied to sorghum seed to minimize injury when the herbicides Dual Magnum or Dual II Magnum are used on sorghum for weed control.2 Observations in wheat elds indicate crop damage when 2,4-D is tank mixed with liquid nitrogen. This also may be evident with other herbicide-nitrogen mixtures. To avoid possible damage and obtain better weed control, herbicides and nitrogen should be applied separately.3 WARNING: THE FOLLOWING STATEMENT HAS BEEN ADDED TO THE ATRAZINE LABEL. THIS STATEMENT SHOULD BE HEEDED BY ALL PROSPECTIVE USERS AND STEPS SHOULD BE TAKEN TO COMPLY WITH THIS LABEL CHANGE. ATRAZINE IS A CHEMICAL WHICH CAN TRAVEL (SEEP OR LEACH) THROUGH SOIL AND CAN CONTAMINATE GROUNDWATER AS A RESULT OF AGRICULTURAL USE. ATRAZINE HAS BEEN FOUND IN GROUNDWATER AS A RESULT OF AGRICULTURAL USE. USERS ARE ADVISED NOT TO APPLY ATRAZINE WHERE THE WATER TABLE (GROUNDWATER) IS CLOSE TO THE SURFACE AND WHERE THE SOILS ARE VERY PERMEABLE, i.e., WELL-DRAINED SOILS SUCH AS LOAMY SANDS. YOUR LOCAL AGRICULTURAL AGENCIES CAN PROVIDE FURTHER INFORMATION ON THE TYPE OF SOIL IN YOUR AREA AND THE LOCATION OF GROUND WATER. IN ADDITION, SOME PRODUCT LABEL STATEMENTS INCLUDE AS A FURTHER QUALIFICATION OF RISKY SOILS, SOILS CONTAINING SINKHOLES OVER LIMESTONE BEDROCK, SEVERELY FRACTURED SURFACES, AND SUBSTRATES WHICH WOULD ALLOW DIRECT INTRODUCTION INTO AN AQUIFER.4 See fact sheet SS-AGR-12 Florida Organo-Auxin Herbicide Rule for state rules pertaining to application of organo-auxin herbicides in Florida. Herbicide recommendations in this report are contingent upon their registration by the Environmental Protection Agency. If a registration is canceled, the herbicide would no longer be recommended.


4Table 2. Estimated Eectiveness of Herbicides on Common Weeds in Florida Sorghum. 1 WEEDS Herbicide Dual or Outlook BasagranPendimax or Prowl AAtrex or Atrazine Banvel or 2,4-DGramoxone Extra Sandea Aim Peak Time of ApplicationPOT/ culti-spray POT PRE POT POT/PDSPDS POTPOTPOTPOT BROADLEAF Bristly starbur P G P E G G-E G -F Cocklebur P E P E E E E F GE Florida beggarweedF-G F F-G G G G-E P -F Florida pusley G-E G G-E E G G -G Morningglories P P P E E G P G FG Pigweed E P E E E G-E G FG-EF Ragweed F F F E E G-E G F GF Sicklepod P P P E E G-E P PF-GP GRASS Crabgrass E P E G P E P P PP Goosegrass E P E G P E P P PP Johnsongrass (from seed) F P F G P E P P PP Sandbur G P G G P E P P PP Texas panicum P P P F-G P E P P PP SEDGE Purple Nutsedge P P P P P F-G G-EP PP Yellow Nutsedge F G F P P F-G G P PP 1 Estimated eectiveness based on herbicide rates recommended in this report. Eectiveness may vary depending on factors such as herbicide, size of weeds, time of application, soil type, and weather conditions. Time of Application PRE = Preemergence POT = Postemergence broadcast PDS = Directed postemergence Weed Control Symbols E = 90-100% control G = 80-90% control F = 60-80% control P = Less than 60% control