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 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 up aphids.
List of additional insecticide options can be found in our cotton insect management guide, here.
Here is our video on how to scout for bollworms: