Fleahoppers and Bollworms

H. zea moth
Kate Harrell

Howdy,

  This week I've seen cotton starting to bloom in all three counties. In the younger cotton we continue to monitor for cotton fleahoppers feeding on squares. In older cotton with blooms I have started looking for bollworms. Bollworms, Helicoverpa zea, are caterpillars that feed on multiple crops and vegetables. In cotton they feed on squares and bolls, causing fruit loss. The last few years we had high numbers of this insect even in our Bt cotton.

H. zea caterpillar in cotton square
Kate Harrell

  To scout for cotton bollworms I use the terminal and square inspection method. I make about four stops in a field, more if the field is larger than 100 acres. At each stop, I look at 25 plant terminals, checking the upper third of the plant for caterpillars and eggs. I also pull 25 half grown or larger green squares to bolls and look for bollworm damage. This week there were a few moths flying around in a couple of the fields in Matagorda county, and in one near Palacios we found two eggs laid. When documenting egg lay, if I find more than one on a leaf, I only count it as one. This caterpillar is highly cannibalistic, and generally only one caterpillar will result from eggs too near each other. The economic threshold for bollworms is 6% damaged bolls with live caterpillars present. In areas like ours on the upper gulf coast with documented Bt failures, the threshold for eggs on single and dual gene cotton is 20% (20 plants out of 100 with at least one egg). If you're finding bollworms in cotton or in corn, especially in viptera fields, please give me a call.

Cotton Insect Guide

 The current A&M recommendation is to use pyrethroids with caution. In areas needing residual control Prevathon at 18-20 fl oz or Besiege at 9-10 fl oz works well. If you don't need residual control you can get by with Prevathon at 14 fl oz or Besiege at 7-8 fl oz.

Cotton Insect Guide

  I know that once it begins to dry we may want to get into the field and add a Plant Growth Regulator to your tank, but please keep in mind that waterlogged conditions also inhibit plant hormones. Be cautious of applying PGRs too soon after heavily waterlogged conditions, as applying PGRs too soon could further decrease yield potential, especially in some varieties. Talk to your seed company about the recommended PGR regiment for each variety.

  I hope everyone has a good weekend and doesn't get too muddy out there! If you're not sure what kind of insect or issue you have, feel free to drop by the Wharton county office or give us a call.

Sincerely,

Kate Harrell

Looking for more information? Check out the Cotton Insect Guide

Need help with weed control? Check out the Weed Management Guide

PGRs after waterlogged conditions

Information on cotton bollworm resistance problems