Fleahoppers and Bollworms

Howdy,

Next Thursday we are hosting a Cotton Scout School at 8:00 am at the Jackson County Services Building in Edna, TX. It's $10 per person to attend, and you can get 2 TDA IPM CEUs. Let us know if you'll be able to attend! Please see the flyer below or give our office a call for more information.

This week we got a good rain across most of the area. Our older cotton is starting to bloom, the soybeans are blooming, and the oldest sorghum is starting to color. The thrips I picked up in soybeans last week were tobacco thrips, and those numbers have dropped significantly with our recent rains.

In sorghum we need to be scouting for sugarcane aphid, I've picked it up in sorghum in all three counties in light numbers now. If it's blooming, we need to look for sorghum midge. Here are some links for just sugarcane aphid, and a more recently updated guide for sorghum insect management. Here are links to the threshold calculators for sorghum midge, rice stink bug, and sorghum headworm. 

Sugarcane Aphids in Sorghum
Kate Crumley

Aphids are still in the cotton, and have been fairly heavy depending on the location. We are picking up fleahoppers, and need to be scouting anything with squares carefully for those. This week we started picking up bollworm eggs, and will be shifting from looking for fleahoppers to looking for bollworms as the fields start to bloom. Below is my scouting information for the week of 5/27/2022. The fields we missed this week were due to rain.

Cotton Aphid
Kate Crumley

The threshold for cotton aphids is 50 aphids per leaf, and if you see aphid mummies in the field (tan or black dry and unmoving aphids), that's a good thing. Parasitoid wasps lay eggs in the aphids, and the aphid forms a mummy while the wasp larvae is pupating inside. These wasps, lady beetles, and lacewings can knock back aphid populations. Treatment for aphids is rarely justified, but if you do decide to treat for aphids, do not use a pyrethroid. Pyrethroids and organophosphates are broad spectrum, and kill beneficial insects as well as your target insect, but pests like aphids bounce back much quicker than their predators do. Their high reproductive rate will allow their numbers to soar after a broad spectrum insecticide application kills all their predators.

Aphid Mummies on Cotton
Kate Crumley

Cotton Fleahopper Adult
Kate Crumley

Fleahopper feeding will cause squares to drop. Plants can recover for and compensate for some square loss, but the threshold for fleahoppers is 15-25 per 100 plants. I check for fleahoppers by inspecting the plant terminals once they start squaring. I look at 25 plants per stop in the field, usually checking 100 plants total in an 80-100 acre field, more if the field is larger. Fleahopper nymphs can be close to the size of aphids, but look like smaller versions of the adults without wings, and are much more mobile than aphids.

The chart below contains insecticide suggestions from cottonbugs.tamu.edu (also a good resource) for reference if you have fleahoppers at the action threshold in the upcoming weeks.

We started picking up bollworm eggs in cotton this week. We found very few, and I've had moderate moth numbers in our traps as well. These 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 in our Bt cotton. They are already in the corn, below is a photo of a caterpillar I pulled from dual gene corn. As the corn matures, the next generation of bollworm eggs will be laid in cotton. I start looking for bollworm eggs in cotton when that field starts blooming.

H. zea Larvae
Kate Crumley

Our Bt traits overlap across corn and cotton. If the caterpillars survive the traits on corn then as adults fly to cotton to lay eggs, it's likely their offspring will survive the same traits on cotton. Below is a chart showing the overlap of Bt traits between crops and technologies.

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. 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).

H. zea Eggs on Cotton
Kate Crumley

I'd also like to let everyone know that there is an Agricultural Pesticide Waste Collection event happening on Wednesday, June 29th from 8:00 am to 12:00 pm at the Victoria County Pct #4 Yard at 226 Beck Road East, Inez, TX 77968. The flyer for that event is below. For any additional questions on this event, please contact the Victoria County Extension Office at (361)-575-4581.

Please check out our weekly IPM Audio Updates, the website to sign up to receive those is listed below. If you have any questions feel free to contact me either by email or calling the office. Have a good memorial day weekend, everyone!

Sincerely,

Kate Crumley

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Cotton Insect Management Guide

Development and Growth Monitoring of the Cotton Plant