Upper Coast IPM: Bugs and Bollworms

Howdy,

I am still seeing a few different plant bug species around, in cotton as well as other crops, but we should be able to stop worrying about damage from these plant bugs in cotton soon. Once bolls get larger and we reach 350 degree days (DD60) past 5 Nodes Above White Flower (NAWF), we can stop scouting for plant bugs. Most of the cotton in my scouting program is between 6 and 3 NAWF.

The threshold for verde plant bugs is 20-25 insects per 100 plants with using a beat bucket. Verdes can feed on fruit up to bolls about an inch in diameter.

Nymph (A) and adult (B) of Verde plant bug, Creontiades signatus Distant (Hemiptera: Miridae), which causes lint and seed staining and deterioration, seen in green (C) and open (D) cotton bolls. https://ccag.tamu.edu/entomology/

I have seen stink bugs in cotton this year, damage thus far has been low, but some locations have needed treatment. To scout for stink bugs pull 10 to 20 bolls about an inch in diameter from four places in the field. Check the inside of the bolls for warts, lesions, and stained lint. The economic threshold for stink bugs is 20% or more of the bolls with internal damage and stink bugs present. Some of the brown stink bug populations in our area have also been shown to have some resistance to pyrethroids.

Green Stink Bug adult
Photo: Kate Crumley

Carpal Wall Warts from Stink Bug feeding damage
Photo: Kate Crumley

This week our scouting was limited with the rainfall, but we still picked up worm pressure, and several places we did not get to check were treated before the rain.

Jackson County

Bollguard 3 near Vanderbilt

12% bollworm eggs
4% small bollworm larvae
6% bollworm damage

Bollguard 2 field near El Toro
12% bollworm eggs
2% small bollworm larvae

5% bollworm damage
2% stink bug damage bolls

Matagorda County

Widestrike near Tin Top

8% bollworm eggs

8% bollworm larvae- 6% large, 2% small
8% bollworm damage squares
4% bollworm damaged bolls

Bollguard 3 near Jackson Matagorda county line on 35

8% bollworm eggs
6% small bollworm larvae
7% bollworm damage
1% stink bug damaged small boll

Widestrike 3 Near Jackson Matagorda county line on 35

8% bollworm eggs
4% small bollworm larvae

8% bollworm damage

Field with a combination of Bollguard 2 and 3 near Palacios

5% bollworm eggs
0% bollworm larvae
8% bollworm damage
4% stink bug damaged small bolls

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 as well. The eggs of this insect are small and white, turning brown as they get closer to hatching. The caterpillars are also highly cannibalistic, the eggs are normally laid singly, but if you find a couple or more on the same leaf, count it as one.

H. zea eggs
Photo: Kate Crumley

H. zea caterpillar in cotton square
Photo: Kate Crumley

H. zea moth
Photo: Kate Crumley

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 at least 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. Recently the egg lay has been in oddball places. We have been finding eggs in the lower 1/3 of the plant, as well as in bloom tags and bracts on fruit. 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.

H. zea eggs on cotton bloom tag
Photo: Ben Crumley

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. I've seen a few places where folks have gone out with imidacloprid and bifenthrin, but this combination does not work well to kill bollworm eggs in the field or moths.

Cotton Insect Guide

Stephen Biles and I recorded our fourth audio update this week. These updates will be going out once a week on what we are seeing going on in our areas. If you are interested in checking that out, you can sign up to receive text updates when we post them on Thursday afternoons at this website https://www.texasinsects.org/signup-co ast.html.

DD60 this season: