Field and greenhouse experiments were conducted to determine the effect on cotton of selected insecticides at rates recommended for thrips (Phorithrips) control when tank-mixed with 1 oz ai/A DPX-PE350. In the field, azinphos, acephate, dicrotophos, oxamil, ethomyl, malathion, chlorpyrifos, bifenthrin, and esfenvalerate were foliarly applied with DPX-PE350 when cotton was 5 to 7 inches high with 4 to 5 leaves. Injury ratings were taken at 5, 7, 10, and 21 days after treatment (DAT). At all ratings, DPX-PE350 plus malathion resulted in greatest injury in comparison to all other treatments. At 21 DAT, DPX-PE350 plus malathion was the only treatment with injury greater than the untreated check. Treatments did not affect cotton yield in two out of three experiments. Yield variations occurred in third late-season test in 1993 and were believed to be a result of varying insect pressure induced by different insecticides.

In the greenhouse, treatments consisted of all possible combinations of 0 or 1 ox ai/A DPX-PE350 with esfenvalerate, malathion, or thiodicarb. After treatment plants were placed in a growth chamber in either a cool or warm environment for three days. Injury due to DPX-PE350 was greater in the warm than the cool environment but was less than 15%. Addition of insecticides to DPX-PE350 did not influence injury in the warm environment. In the cool environment plants treated with DPX-PE350 plus malathion resulted in more severe injury 7 and 14 DAT than either pesticide alone.