Upper Coast IPM: Cutout and Cracked Bolls

Howdy,

There are a lot of fields blooming out the top, and we found our first cracked boll this week. The cotton crop is wrapping up around here. Cutout occurs when cotton is 5 Nodes Above White Flower (NAWF), and at 350 degree days (DD60) past cutout we can stop worrying about plant bugs and bollworms. We can stop worrying about stink bugs at 450 DD60 past cutout, so keep that in mind while scouting and if you are considering treatment. The bolls they are feeding on past this point are bolls that will not reach maturity by harvest anyway, as the ones that are going to be harvested have grown too hard for them to feed on.

DD60 this season:

I've seen stink bug damage picking up the last couple of weeks. 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's scouting report numbers:

Jackson County

Bollguard 3 near Vanderbilt
16% bollworm eggs
4% small bollworm larvae
18% bollworm damage

Bollguard 2 field near El Toro
14% bollworm eggs

Bollguard 3 field near La Salle
21% bollworm eggs
10% bollworm damage

Matagorda County

Widestrike near Tin Top
1% bollworm eggs
4% bollworm damage

Bollguard 3 field near Tidehaven
10% bollworm eggs
7% bollworm damage

Field with a combination of Bollguard 2 and 3 near Palacios
1% bollworm damage

Widestrike 3 field off 35 near Jackson Matagorda county line
4% bollworm eggs

Widestrike 3 field off 35 near Jackson Matagorda county line
8% bollworm eggs
6% bollworm damage
2% stink bug damage

Wharton County

Widestrike 3 in Blue Creek Area
10% bollworm eggs
8% small worms
12% bollworm damage

Bollguard 2/3 in Blue Creek Area
20% bollworm eggs
3% small worms
9% bollworm damage

Bollguard 2/3 in Blue Creek Area
17% bollworm eggs
3% small worms
11% bollworm damage

Widestrike 3 field near Danavang
6% bollworm eggs
3% bollworm damage
3% bollworm damaged bolls

Bollguard 2 near Crescent
1% bollworm damage
2% stink bug damage

Bollguard 3 near Crescent
12% bollworm eggs
6% bollworm damage

Bollguard 3 near Crescent
4% bollworm eggs

Widestrike 3 near Fairgrounds
6% bollworm eggs
6% small worms
4% bollworm damage
2% bollworm damaged bolls

Bollguard 3 near Egypt
4% bollworm eggs
2% stink bug damage

Bollworms 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, 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 another 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.

On June 17th Laramie Naumann got folks together to film Colorado County's video field day. That video can be found at https://youtu.be/9VB9gZLH9EM.

Stay safe, and have a happy 4th of July, yall!

Sincerely,

Kate Crumley

For More Information:

Cotton Insect Guide

Aphids in Cotton