 |
| Cotton Bloom Photo: Kate Crumley |
Howdy,
This Wednesday the United States Court of Appeals for the Ninth Circuit issued a ruling vacating the federal registration for three dicamba herbicide products, Xtendimax, FeXapan, and Engenia. I know several of you have questions on this, and the links below are the most up to date info I've seen on this:
The Jackson county Ag Tour will be taking place on Monday, June 15 at 4:00 pm. The tour starts at the sorghum demonstration on the Kulak Farm on CR 325 north of La Salle. There will be 2 CEU credits available for $10. More information on the crop tour can be found at: https://jackson.agrilife.org/files/2020/05/2020-Jackson-County-Ag-Tour.pdf
Stephen Biles and I recorded our second 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-coast.html.
I spent most of this week in the mud again, but our insect pressure is still low. Cotton is out of danger of economic yield reduction from fleahoppers once it starts blooming. I only have one field I am looking at still susceptible to fleahoppers, and it was treated with Centric this week. We found 2.5% fleahoppers a couple days after treatment, all adults.
I am still seeing a few different plant bug species around, though in lower numbers this week. I picked up one verde plant bug this week. 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.
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.
The chart above with action thresholds if from the cotton insect guide, and the one below containing insecticide suggestions is from cottonbugs.tamu.edu.
Lygus bugs will feed on cotton squares, flowers, and small bolls. Feeding can cause damage to blooms (dirty blooms and damaged anthers, or puckered petals), deformed bolls, stunted growth, fruit shed, and small lesions on bolls.
I have only seen one stink bug in cotton so far this year, but now that our cotton is putting bolls on we need to look for them. 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.
I have not seen any bollworms, Helicoverpa zea, in fields yet this year, but I have started picking up low numbers of eggs. In Wharton county we picked up 2% eggs and 4% damaged squares in a field near the fairgrounds, 0% eggs, 2% eggs and 0 damaged squares, and 6% eggs and 6% damaged squares, and 0% in one south west of the fairgrounds. In the blue creek are we found 4% eggs with 4% damaged squares, and 3% eggs with 1% damaged squares in another. Near Danavang we found no eggs but 1% damaged squares. Near Egypt we found no eggs but 2% damaged squares. There were 4% eggs and 6% damaged squares in a field near the airport.
I am still seeing a few different plant bug species around, though in lower numbers this week. I picked up one verde plant bug this week. 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/ |
If you're still susceptible fleahoppers, they are an insect that feeds on plant materials, and will feed on cotton squares. Keep a sharp eye out for this insect, the adults are very flighty and are often easily scattered when walking fields. I try not to let my shadow hit a plant before I get close enough to look at it so I can see the adults before they fly. Below I have two photos, one of the nymph and one of the adult insect. The nymphs of these insects are also quite small, about the size of an aphid. They are also a pale green color, but lack wings. They lack cornicles (tailpipes) that an aphid would have, and tend to be more mobile than an aphid. Fleahopper nymphs also lack the bands on the antennae a few other species of plant bugs have, and have a similar body shape to the adult bug.
 |
| Cotton Fleahopper Nymph Photo: Kate Crumley |
 |
| Cotton Fleahopper Adult Photo: Kate Harrell |
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.
Lygus bugs will feed on cotton squares, flowers, and small bolls. Feeding can cause damage to blooms (dirty blooms and damaged anthers, or puckered petals), deformed bolls, stunted growth, fruit shed, and small lesions on bolls.
 |
| Lygus Bug nymph Photo: Kate Crumley |
 |
| Lygus Bug adult Photo: Kate Crumley |
 |
| Chart from Cotton Insect Guide |
 |
| Green Stink Bug adult Photo: Kate Crumley |
 |
| Carpal Wall Warts from Stink Bug feeding damage Photo: Kate Crumley |
I have not seen any bollworms, Helicoverpa zea, in fields yet this year, but I have started picking up low numbers of eggs. In Wharton county we picked up 2% eggs and 4% damaged squares in a field near the fairgrounds, 0% eggs, 2% eggs and 0 damaged squares, and 6% eggs and 6% damaged squares, and 0% in one south west of the fairgrounds. In the blue creek are we found 4% eggs with 4% damaged squares, and 3% eggs with 1% damaged squares in another. Near Danavang we found no eggs but 1% damaged squares. Near Egypt we found no eggs but 2% damaged squares. There were 4% eggs and 6% damaged squares in a field near the airport.
In Jackson county we found 4% eggs in a field near El Toro with no damaged squares, 0% near Vanderbilt, and 1% eggs with no damaged squares near the county line off 35.
In Matagorda county we found 2% eggs and 1% damaged squares near Tidehaven, 0% at Tin Top, and 0% near Palacios.
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 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 |
Stay safe and have a good weekend everyone!
Sincerely,
Kate Crumley
For More Information:
No comments:
Post a Comment