Friday, December 2, 2022

Bollworms moving from corn threaten Texas High Plains cotton

• By Patrick Porter, Kerry Siders and Suhas Vyavhare •

bollworm feeing on boll
A bollworm feeds on a cotton boll — photo courtesy Texas A&M AgriLife Research

The current spike in bollworm moth activity in our pheromone traps is from moths coming out of corn. These moths pose a substantial threat to cotton with majority of our fields being in peak bloom.

I have not noticed significant worm activity in cotton yet, but last week we did start to pick some worm damage in our research plots of non-Bt cotton. The amount of fruit damage in non-Bt cotton ranges from 0-2%.

This is expected to increase over the next few weeks as more moths coming out of corn land in cotton. It is important to scout cotton twice a week irrespective of Bt technology. Bt resistance in bollworm field populations being widespread, under high insect pressure we may need to spray some of our two-gene Bt fields.

In all cotton (Bt or non-Bt), treatment is recommended if 6% fruit damage (mix of squares and bolls) is observed.

The diamide insecticides, Besiege (7-10 fl oz/acre) or Prevathon (14-20 fl oz/acre), are the most effective products to control bollworm. These products provide about two weeks of residual control.

With a higher rate, longer residual control can be obtained. If you are finding stink bugs as well, Besiege will provide control against both worms and stink bugs. However, if there are no stink bug issues, it is best to avoid unnecessary pyrethroid applications as they can flare aphids.

A list of additional insecticide options can be found in our cotton insect management guide:

Dr. Patrick Porter is an Extension entomologist, Kerry Siders is an Extension IPM agent and
Dr. Suhas Vyavhare is an Extension Entomologist. All work for Texas A&M AgriLife Research in the South Plains.

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