ABSTRACT
Twenty-five experiments were conducted during 1986, across the Eastern cotton-belt, to evaluate the response of various broadleaf weeds by size to post-directed applications of methazole and methazole plus MSMA at methazole rates of 0.25 to 0.75 lbs ai/A. Cotton production practices were similar to those employed by local growers. Experiments were rated by visual estimate for broadleaf control and crop injury 4 to 13 days after treatment. Crop injury was transitory and ranged from 0 to 20 percent. Injury was mostly 10 percent or less. The addition of MSMA at 1.65lbs ai/A to methazole applications of 0.25 to 0.75lbs ai/A resulted in no observable differences in broadleaf weed control if weeds were 2" or less. However, if weeds were greater than 2" and less than 3", MSMA a eared to increase control by 7 to 19 percent up to a methazole rate of 0.625 lbs ai/A. At a methazole rate of 0.75 lbs ai/A, no apparent differences were observed. The following discussion pertains to the methazole plus MSKA applications with MSMA applied at 1.65 lbs ai/A in all treatments. Pitted and entireleaf morningglory control, with an application of methazole, was acceptable (82%) at a rate of 0.375 lbs ai/A and excellent (907+) at 0.50 to 0.75 lbs ai/A when morningglories were 2" or less. If morningglories were greater than 2" and less applied at 0.50 and 0.625 lbs ai/A control (84 and 82%, respectively) provided excellent control (91%). larger than 3" were not controlled methazole rate. Good prickly sida than 3" methazole gave acceptable and 0.75 lbs ai/A Morningglories acceptably at any control (87%) was obtained with a methazole application of 0.50 lbs ai/A and excellent control was observed with rates of 0.625 and 0.75 lbs ai/A (90 and 94%, respectively) when the weeds were 2" or less. When prickly sida was greater than 3" no treatment gave acceptable control. Spotted spurge was more difficult to control and methazole applications gave marginally acceptable control at 0.625 and 0.75 lbs ai/A (76 and 78%, respectively), when the weeds were 2" or less. If the spotted spurge was greater than 2" and less than 3" only methazole at 0.75 lbs ai/A gave marginally acceptable control (77%). Combining data for all broadleaf species indicates that acceptable weed control (80%+) would be obtained with 0.50 lbs ai/A of methazole applied in combination with MSMA to weeds 2" or less. If weeds are 2" to 3" then 0.75 lbs ai/A of methazole would be required for acceptable control. Averaging across all species would indicate that if weeds are greater than 3" acceptable control may be obtained with 0.75 lbs ai/A of methazole, however, the above discussion points out that morningglories, prickly sida, and spotted spurge may not be acceptably controlled when this large. This research supports the generally accepted guideline that weeds should be treated when 2" or less and that only increased herbicide rates will provide control of weeds up to 3" weeds larger than 3" should not be treated.
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