ABSTRACT
Field studies were conducted in 1994, 1995, and 1996 at the Delta Research and Extension Center, Stoneville, MS to determine the most appropriate application timing of malathion relative to postemergence pyrithiobac producing the least incidence of cotton injury. Treatments consisted of pyrithiobac at 70 g ai/ha applied post-over-the-top (E-POT) with malathion applied at 1 or 3 days before, at E-POT, and at 1 or 3 days after pyrithiobac application. Dimethoate and esfenvalerate were applied only in combination with pyrithiobac at E-POT. Cotton was treated approximately one month after planting. At 7 DAT, pyrithiobac plus malathion applied E-POT caused the highest incidence of injury ranging between 22 and 34%. Malathion applied 1 day before E-POT resulted in 15 to 18% injury while applied 1 day after pyrithiobac application injured cotton 11% and 15%. Injury of cotton subjected to malathion applied 3 days before or after malathion application or pyrithiobac alone was not significantly different. At 21 DAT, all treatments containing malathion caused 6% or less injury. Seed cotton yield was not adversely affected by treatments containing pyrithiobac plus malathion compared to pyrithiobac applied alone.
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