The Effects of Sub-Lethal Rates of Glyphosate on Regrowth Control, Lint Yield and Fiber Quality

Juan A. Landivar, Darlene Locke, Daryl Moseley


The use of strippers to harvest cotton requires the elimination of all green material from plants to avoid green staining, trash content and accumulation of heat in cotton modules. The recent removal of arsenic acid from the market has influenced researchers to explore alternative methods for suppressing regrowth. We propose the use of sub-lethal rates of the herbicide glyphosate to control regrowth in cotton. The specific objective of the study is to evaluate the effect of glyphosate applied at 10% open boll (OB) on regrowth inhibition, lint yield and fiber quality. The experiment was conducted at the Texas A&M Research and Extension Center at Corpus Christi, Texas, during the 1993 growing season. The experimental treatments were: untreated check (UTC), glyphosate at the rates of 114, 171 and 228 g a.i. acre-1, which are equivalent to 0.50, 0.75, and 1.00 pint of Roundup (RU) acre-1, respectively. In order to evaluate the effect of time of RU application on regrowth inhibition, additional applications of 0.50 and 0.75 pint RU acre-1 were made at 50% OB. All plots received 0.1 and 2.0 lbs per acre-1 of Dropp and Prep, respectively at 70% maturity. Final harvest was conducted on August 16 and regrowth was evaluated on September 15. Levels of regrowth control obtained in this experiment demonstrated that glyphosate may be a cost effective technique used to inhibit regrowth in cotton production in the Lower Coastal Bend Region of Texas. The application of 0.50 pints of RU acre-1 at 10% OB was effective in suppressing regrowth for as long as 55 days (or more) after application (from July 20 until September 15), without a significant effect on lint yield or fiber quality.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pp. 1276 - 1278
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998