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Permanent Link: http://ufdc.ufl.edu/IR00002456/00001
 Material Information
Title: Weed Management in Transgenic, Herbicide-Resistant Soybeans
Physical Description: Fact Sheet
Creator: Ferrell, Jason A.
Publisher: University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication: Gainesville, Fla.
Publication Date: 2004
 Notes
Acquisition: Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Melanie Mercer.
Publication Status: Published
General Note: "Revised April 2004."
General Note: "SS-AGR-11"
 Record Information
Source Institution: University of Florida Institutional Repository
Holding Location: University of Florida
Rights Management: All rights reserved by the submitter.
System ID: IR00002456:00001


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SS-AGR-11 Weed Management in Transgenic, Herbicide-Resistant Soybeans1 J.A. Ferrell, G. E. MacDonald, B. J. Brecke, and J. Tredaway Ducar2 1. This document is SS-AGR-11, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Revised April 2004. Original written by J. Tredaway Ducar, revised by J.A. Ferrell and G. E. MacDonald. Please visit the EDIS Website at http://edis.ifas.ufl.edu. 2. J.A. Ferrell, assistant professor, Agronomy Department; G. E. MacDonald, assistant professor, Agronomy Department; B. J. Brecke, professor, Agronomy Department, West Florida Research and Education Center-Milton, FL; J. Tredaway Ducar, former assistant professor, Agronomy Department. 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 specific 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 manufacturer's label. All chemicals should be used in accordance with directions on the manufacturer's label. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity Affirmative Action Employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Larry R. Arrington, Interim Dean Transgenic or herbicide-resistant soybeans are genetically altered to tolerate (the actual resistance is altered enzyme) herbicides that would normally kill or injure conventional or non-transgenic varieties. This genetic modification allows the use of broadspectrum herbicides over-the-top of soybeans and provides economical and efficient weed management. The transgenic soybean varieties which are commercially available are Roundup Ready and Libery Link. Using transgenic varieties can expand weed management options while providing a more convenient and effective method of weed control. The following section provides information regarding herbicide applications for Roundup Ready and Liberty Link varieties. This is not intended to substitute for herbicide labels, which should be carefully read prior to planting these varieties. Roundup Ready Soybeans Roundup Ready varieties are genetically altered to tolerate over-the-top applications of glyphosate, Roundup WeatherMax, Glyphomax Plus, Glyphomax, Touchdown and several other products containing glyphosate. However, be sure to check the product label for use on all Roundup Ready soybeans. Glyphosate controls most annual grasses and broadleaf weeds. The Roundup Ready system has been most successful where soybeans are drilled in 7to 10-inch rows, where fields are scouted early, and when timely applications are made. Producers are encouraged to keep good records of planting to avoid spraying non-transgenic resistant fields with glyphosate. Drift to adjacent crops should be avoided. Sprayers should be cleaned thoroughly and flushed prior to and after application. Application Timing Glyphosate can be applied anytime from the cracking stage throughout flowering. Multiple applications can be made, but

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Weed Management in Transgenic, Herbicide-Resistant Soybeans 2 should not exceed the recommended limit on the label. Application rates are dependent on weed species and size, therefore, consult label for this information. Timely application is required. The first application should usually be made 16 to 20 days after planting; repeat applications can be made if needed. In narrow-row soybeans under good growing conditions, a single application is often sufficient. Wide-row soybeans normally require either a preemergence herbicide followed by glyphosate or two postemergence applications. Herbicide program Any registered soil-applied herbicide can be used on Roundup Ready soybeans. Soil-applied herbicides are generally not needed with timely postemergence applications except for fields with Florida pusley. Use of soil-applied herbicides will, however, make the timing of postemergence herbicides less critical and usually eliminate the need for a second application. Consult the manufacturer label for use rates. The addition of Cobra or Ultra Blazer will aid in morningglory control. For additional information on the weeds controlled by other herbicides, see the Estimated Effectiveness of Recommended Herbicides on Common Weeds in Florida Soybeans table. This table is for both transgenic and conventional varieties. Liberty Link Soybeans Liberty Link varieties are genetically altered to tolerate over-the-top applications of glufosinate, the active ingredient of Liberty. However, be sure to check the product label for use on all Liberty Link soybeans. Glufosinate controls many broadleaf weeds and some grasses. Liberty is a contact herbicide with limited translocation within in the plant. Therefore, spray coverage is essential to effective control. Also, since translocation is reduced, the activity of Liberty on perennial weeds can be limited. The Liberty Link system has been most successful where soybeans are drilled in 7to 10-inch rows, where fields are scouted early, and when timely applications are made. Producers are encouraged to keep good records of planting to avoid spraying non-transgenic resistant fields with glufosinate. Drift to adjacent crops should be avoided. Sprayers should be cleaned thoroughly and flushed prior to and after application. It must be noted, Roundup Ready Soybeans will NOT tolerate applications of Liberty and vice versa. Application Timing Glufosinate can be applied anytime from the cracking stage throughout flowering. Application rates are 24 to 34 oz/A and no more than 62 oz/A/yr may be applied. Application rates are dependent on weed species and size, therefore, consult label for this information. Timely application is required. In narrow-row soybeans under good growing conditions, a single application may sufficient, depending on the weed spectrum. Wide-row soybeans normally require either a preemergence herbicide followed by glufosinate or two postemergence applications. Herbicide program Any registered soil-applied herbicide can be used. Soil-applied herbicides are generally not needed with timely postemergence applications except for fields with Florida pusley. Use of soil-applied herbicides will, however, make the timing of postemergence herbicides less critical and usually eliminate the need for a second application. Consult the manufacturer label for use rates. For additional information on the weeds controlled by other herbicides, see the Estimated Effectiveness of Recommended Herbicides on Common Weeds in Florida Soybeans table. This table is for both transgenic and conventional varieties.

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Weed Management in Transgenic, Herbicide-Resistant Soybeans 3 Table 1. Estimated effectiveness of recommended herbicides on common weeds in Florida soybeans.1 Herbicides Treflan, Prowl, Sonalan First Rate Liberty Glyphosate Time of Application PPI POT POT POT WEEDS BROADLEAF Bristly starbur P E G G-E Crotalaria P -F-G Cocklebur P E G G-E Florida beggarweed P F-G G G Florida pusley E F F-G F Morningglory2 P G G F-G Pigweed E P F-G G Ragweed P E G G Sicklepod (coffeeweed) P F G G Smartweed P -G Wild Poinsettia P G G G-E GRASS Junglerice E P G Crabgrass E P G E Fall panicum G-E P G-E E Goosegrass E P F-G E Sandbur E P G Johnsongrass (seed) E P G E Johnsongrass (rhizome) P P P-F G Texas panicum E P G-E E

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Weed Management in Transgenic, Herbicide-Resistant Soybeans 4 Table 1. Estimated effectiveness of recommended herbicides on common weeds in Florida soybeans.1 Herbicides Treflan, Prowl, Sonalan First Rate Liberty Glyphosate SEDGES Purple Nutsedge P P P-F F-G Yellow Nutsedge P P P-F F-G 1 Estimated effectiveness based on herbicide rates recommended on the label. Effectiveness may vary depending on factors such as herbicide rate, size of weeds, time of application, soil type, and weather conditions. 2 Check label for particular species control differences. Weed Control Symbols: E = 90-100% control; G = 80-90% control; F = 60-80% control; P = less than 60% control; -= insufficient observations. Time of Application: PPI = preplant; PRE = preemergence; POT = postemergence over the top. Table 2. Estimated effectiveness of recommended herbicides on common weeds in Florida soybeans. Herbicides Classic Goal Blazer, Cobra Poast Plus, Fusilade, Select, or Assure II Time of Application POT PDS POT POT WEEDS BROADLEAF Bristly starbur E F P-F P Crotalaria -F E P Cocklebur E E E P Florida beggarweed G G P-F P Florida pusley F F E P Morningglory G2 G E P Pigweed E G E P Ragweed E G E P Sicklepod (coffeeweed) G F P P Smartweed E G -P

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Weed Management in Transgenic, Herbicide-Resistant Soybeans 5 Table 2. Estimated effectiveness of recommended herbicides on common weeds in Florida soybeans. Herbicides Classic Goal Blazer, Cobra Poast Plus, Fusilade, Select, or Assure II Wild Poinsettia G -F-G P GRASS Junglerice P F P G-E Crabgrass P F P G-E Fall panicum P F P G-E Goosegrass P F P G-E Sandbur P F P G-E Johnsongrass (seed) P P P G-E Johnsongrass (rhizome) P P P G-E Texas panicum P F P G-E SEDGES Purple Nutsedge F P P P Yellow Nutsedge F P P P 1 Estimated effectiveness based on herbicide rates recommended on the label. Effectiveness may vary depending on factors such as herbicide rate, size of weeds, time of application, soil type, and weather conditions. 2 Check label for particular species control differences. Weed Control Symbols: E = 90-100% control; G = 80-90% control; F = 60-80% control; P = less than 60% control; -= insufficient observations. Time of Application: PPI = preplant; PRE = preemergence; POT = postemergence over the top; PDS = postemergence directed.