Herbicide drift from aerial application to non-target crops has been a problem in Arkansas. Drift from rice herbicides is probably the greatest concern to cotton producers in Arkansas. In 1989, drift from 2,4-D affected 10,000 acres of cotton. In 1990, 3,705 acres were affected by 2,4-D drift. Complaints of 2,4-D drift were up from 22 in 1989 to 59 in 1991.

In 1989 and 1990, cotton response was evaluated for effects of imazaquin, glyphosate, and triclopyr. Field trials were conducted at the Southeast Branch Experiment Station, Rohwer, AR. Stoneville 506 cotton was planted both years. Herbicides were applied directly over the top of the cotton at two growth stages, cotyledon and early fruiting.

Cotton was treated with 0.5, 0.1, and 0.01x rates of imazaquin, (0. 063, 0.013, and 0. 001 lb ai/A), glyphosate, (0.25, 0.05, and 0.005 lb ai/A), and triclopyr (0.188, 0.038, and 0.004 lb ai/A).

All treatments caused visual crop injury. Data will only include effects on maturity and yield. None of the herbicides delayed maturity (just prior to harvest) or reduced cotton yield at the 0.01x rate. Imazaquin and glyphosate delayed maturity and reduced yield at the 0.1x rate when applied to cotyledon cotton. Imazaquin and triclopyr at the 0.1x rate applied to early fruiting cotton delayed maturity and decreased cotton yield. Imazaquin, glyphosate, and triclopyr at the 0.5x rate delayed maturity and reduced yield at both growth stages.

A similar experiment was conducted in 1991 at the Southeast Branch Experiment Station. Herbicides evaluated were quinclorac, triclopyr, bensulfuron, and 2,4-D amine. Stoneville 506 cotton was treated at the cotyledon and early fruiting growth stages.

Cotton was treated with 0.5, 0.1, and 0.01x rates of quinclorac, (0.25, 0.05, and 0.005 lb ai/A), triclopyr, (0.188, 0.038, 0.0038 lb ai/A), and bensulfuron, (0.5, 0.1, and 0.01 oz ai/A). 2,4-D was applied at 0.01 and 0.00lx rates (0.005 and 0.0005 lb ai/A).

Data will only include effects on maturity and yield. 2,4-D at the 0.001x rate did not affect maturity or yield at either growth stage. The 0.01x rate of 2,4-D applied to early fruiting cotton resulted in a yield reduction. None of the other herbicides at the 0.01x rate delayed maturity or reduced yields. None of the herbicides affected maturity or yield at the cotyledon growth stage. Quinclorac at the 0.1x rate applied to early fruiting cotton reduced yield. Quinclorac and triclopyr at the 0.5x rate applied to cotyledon cotton delayed maturity, but only quinclorac reduced cotton yield. Quinclorac and triclopyr at the 0.5x rate applied to early fruiting cotton delayed maturity and reduced cotton yield. Bensulfuron did not affect cotton maturity or yield at 0.5, 0.1, or 0.01x rates at either growth stages.