Full Text
(39 K)

Application of Sub-Lethal Rates of Glyphosate to Control Regrowth in Cotton: Summary of Three Years Research

J.A. Landivar, K. Creekmore, D. Moseley


The banning of the use of arsenic acid to quickly desiccate regrowth prior to harvest has influenced researchers to investigate alternative methods for suppressing regrowth in cotton. Treatments aimed at inhibiting root growth as the boll load matures may help to suppress regrowth in cotton plants. The herbicide glyphosate is readily absorbed by the foliage and is efficiently translocated to actively growing tissues of the plant. Glyphosate may be an effective chemical to hamper new root growth thus leading to the inhibition of top regrowth. This series of studies proposes the use of sub-lethal rates of glyphosate to control regrowth in cotton. Specific objectives of the study were; (1) to determine the effect of time and (2) rate of application on growth parameters, lint yield, fiber quality and planting seed quality. Experiments were conducted at Corpus Christi, Texas during 1993, 1994 and 1995. Source of glyphosate for the study was Roundup (RU) which contains 41% of active ingredient. The applications of RU were made at various stages of crop maturity, prior to final defoliation. Conclusions and recommendations are as follows; (1) the application of sub-lethal rates of glyphosate is an effective means of controlling regrowth in cotton, (2) rate of application has a direct effect on level of regrowth inhibition, (3) applications made at less that 20% maturity (open boll) can reduce yield and micronaire, (4) applications made after 50 to 60% maturity are not as effective in controlling regrowth as applications made at 20 to 50% maturity, (5) sub-lethal rates of glyphosate can enhance defoliation efficiency and (6) the use of glyphosate as a harvest-aid chemical severely affects seed vigor. Recommendations for use of this technique are: (1) apply 12 to 16 oz. RU acre-1 at 30 to 50% open boll stage to inhibit regrowth, (2) as the time of application approaches 50% maturity, increase the rate of RU to 14-16 oz. acre-1, (3) increase the rate to 14 to 16 oz. acre-1 for rank cotton or for years with high soil moisture at harvest, (4) delay the time of application and/or use a lower rate if growing conditions are conducive to low micronaire, and (5) do not use this technique if you plan to save the seed for planting purposes.

Reprinted from Proceedings of the 1996 Beltwide Cotton Conferences pp. 1161 - 1164
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
Document last modified Sunday, Dec 6 1998