ABSTRACT

In the past 10 years, cotton stalk destruction deadlines were established within three Texas Boll Weevil Eradication Zones on the Texas Gulf Coast to eliminate hostable cotton plants capable of supporting overwintering boll weevils. In South Texas, only 35% of all harvested cotton acreage was destroyed with chemical treatments in 2003. Chemical usage is increasing because stalk destruction is made easier than mechanical methods, and better results are obtained. In 8 regional stalk destruction tests, rates of 0.5, 1.0 and 1.5 lbs/A of 2,4-D amine were evaluated to terminate standing cotton stalks, flay-shredded and sheared cotton stubble, immediately following wounding. Delays in chemical application after harvest/shredding were evaluated at 1, 2, 7, 14 or 35 days post-harvest. Best results were obtained when flay-shredded stalks were treated with 1.0 or 1.5 lb/A 2,4-D immediately following shredding. Due to limited wound surface area, sheared stalks and standing stalks did not suppress as well as flay-shredded stalks. All three 2,4-D treatment rates and application delays made within one and two days of harvest did not produce squares in 45+ days. Untreated, shredded plants produced squares in 32 days, while untreated, harvested whole plants produced new squares in as little as 26 days. In a follow-on study, sixty-two commercially available and experimental cotton varieties were evaluated for regrowth at 35 days after shredding. Vast differences in mechanical plant death were observed following flay-shredding, and regrowth vigor is reported on a scale of 1-5. As high as 80 percent plant death was observed with the mechanical shredding of FiberMax 832. Glyphosate, Liberty, Gramoxone, Buctril, Direx, Linex, Goal and Valor were also evaluated to terminate cotton seedlings and to suppress regrowth near urban areas where 2,4-D usage is discouraged. Results from six of 14 locations are reported of those evaluated in 2003.