West Texas Cotton: Scout for Aphids and Bollworms
Suhas Vyavhare, Extension Cotton Entomologist, Texas A&M AgriLife Extension Service
Cotton will benefit from some of the timely rainfall we have been receiving recently. However, it is going to make conditions better for survival and multiplication of several pest species as well. In general, the hot and dry weather of West Texas helps to keep bollworm numbers in check (through desiccation of eggs). Humid and cloudy conditions over the last couple of weeks, however, may increase egg hatch rate and worm survival in cotton. In addition, added new growth on plant terminals will help both bollworms and aphids thrive better.
I have also come across a few reports of bollworm damage to non-Bt cotton. In our research trials, bollworm damage ranges from 5-6% boll injury in non-Bt cotton and <1% in Bt cotton. The threshold is 6% fruit injury with the presence of live worms in both Bt and non-Bt crop. Among various insecticide options for bollworm control, Diamide insecticides (Prevathon and Besiege) are the most reliable choices. Remember, Besiege contains both a diamide and a pyrethroid so it would be a better choice if stink bugs are present too. However, if aphid colonies are present in the field, the pyrethroid component may flare-up aphids. If a field needs to be treated for both aphids and bollworms, Prevathon can be tank-mixed with any of the commonly used aphidicides such as acetamiprid (Intruder).
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