Thursday, August 27, 2020

Sesame Leafroller Now Widespread on the High Plains

Sesame leafroller is a major pest of the crop, and we have tracked its movement north this year. This is a new pest for us. Dr. Emi Kimura, our agronomist in Vernon, reported it last week. This week Drs. Qingwu Xue and Jourdan Bell reported it at Bushland, and one of our superb Independent Crop Consultants reported it at Abernathy just north of Lubbock and made comment that he treated the field three weeks ago and now had to treat again. He also just today reported it near Gruver in the northern Panhandle.

Dr. Holly Davis, Extension Entomologist in Weslaco, recently posted a nice blog article and video on sesame leafroller, so I won't duplicate that information here. She conducted an insecticide efficacy trial which showed pyrethroids don't work all that well. She also found that the 8 oz and 12 oz. rates of Prevathon worked very well, and the 8 oz rate did just as good a job. (The difference will be that the 12 oz rate will provide longer residual control.) Blackhawk also worked very well at 1.1 and 2.2 oz, but Blackhawk is not labeled for use on sesame. 

Here are some photos from near Abernathy today.

Sunday, August 23, 2020

South Plains cotton: questions related to Lygus bug

 At what stage cotton is safe from Lygus bug?

No treatment is needed once cotton reaches 350 DD60s beyond cutout (5 NAWF).  

 What is the threshold for Lygus bug after peak bloom?

Use of drop cloth is the best way to measure plant bugs after peak bloom. Treatment thresholds based on drop cloth sampling is 4 to 6 Lygus bugs per 6-foot row.

 What insecticides to use to manage lygus bug in cotton?

Below is a table with the list of suggested insecticides. Add Transform to the list.


Would these products provide control against stink bugs too?

Acephate and Bidrin has a good activity against stink bugs. However, other plant bug products alone (e.g. Transform, neonicotinoids) will only provide some level of stink bug suppression and will not be enough to effectively control them.

Tip: Do not confuse seed bugs or scentless plant bugs with Lygus. Although fairly common, scentless plant bugs feed mostly on weeds and are harmless to cotton.  


Lygus bug (photo: Pat Porter) 

Scentless plant bug
Scentless plant bug 

Texas High Plains cotton: stink bug remains quiet

Cotton fields that have accumulated 450 DD60 (degree days 60) beyond cutout (5NAWF) are generally safe from an economic damage from stink bugs. Late planted and heavily irrigated fields with fairly high number of young bolls still need to be scouted for stink bugs. Stink bug feeding on young bolls (<10 days old) usually causes the bolls to shed. In larger bolls, stink bug feeding often results in dark spots ~1/16 inch in diameter on the outside of bolls. These dark spots do not always correlate well with the internal damage—callus growths or warts and stained lint. Damage to the internal boll wall is a good indication that lint and seed are affected.

Base decisions to treat for stink bug infestations on the percentage of bolls with evidence of internal damage (warts or stained lint associated with feeding punctures).  To use this technique: Remove about 10 to 20 bolls, one inch in diameter (about the size of a quarter), from each of four parts of the field, avoiding field edges. Break open the bolls by hand or cut them with a knife. Look for internal warts on the boll walls and stained lint on the cotton locks. Check bolls with visible external lesions first to determine if the internal damage threshold has been met because bolls with external lesions are more likely to also be damaged internally.

Use a 10 percent to 15 percent boll injury threshold during weeks 3 through 5 of bloom and 20-30 percent during weeks 6 or later of bloom. If using drop cloth or whole plant inspection method, detection of 1 stink bug per 6 row-feet would also justify treatment. Pyrethroids or organophosphate (e.g. Bidrin, Orthene) insecticides provide a good control against conchuela stink bug which is the primary species we encounter. Products targeted at plant bugs such as Transform, Carbine, Diamond, and neonicotinoids will not be sufficient to control stink bugs. For the mix of stink bug and plant bugs, either Bidrin or acephate would be a good choice or a tank mix of plant bug product (e.g. Carbine, Diamond, Transform, neonicotinoids) and a pyrethroid or acephate. Detailed list of suggested insecticides can be found at: https://lubbock.tamu.edu/files/2019/08/2019-Cotton-Insect-Control-Suggestions_ENTO090.pdf

Sunday, August 2, 2020

Texas High Plains cotton: keep an eye out for bollworms

The current spike in bollworm moth activity in our pheromone traps is from moths coming out of corn. These moths pose a substantial threat to cotton with majority of our fields being in peak bloom. I have not noticed significant worm activity in cotton yet but last week we did start to pick some worm damage in our research plots of non-Bt cotton. The amount of fruit damage in non-Bt cotton ranges from 0-2%. This is expected to increase over the next few weeks as more moths coming out of corn land in cotton. It is important to scout cotton twice a week irrespective of Bt technology. Bt resistance in bollworm field populations being widespread, under high insect pressure we may need to spray some of our two-gene Bt fields. In all cotton (Bt or non-Bt), treatment is recommended if 6% fruit damage (mix of squares and bolls) is observed.

The diamide insecticides, Besiege (7-10 fl oz/acre) or Prevathon (14-20 fl oz/acre), are the most effective products to control bollworm. These products provide about two weeks of residual control. With higher rate, longer residual control can be obtained. If you are finding stink bugs as well, Besiege will provide control against both worms and stink bugs. However, if there are no stink bug issues, it is best to avoid unnecessary pyrethroid applications as they can flare up aphids.  

 List of additional insecticide options can be found in our cotton insect management guide: https://lubbock.tamu.edu/files/2019/08/2019-Cotton-Insect-Control-Suggestions_ENTO090.pdf

 Here is a link to our video on how to scout for bollworms: https://www.youtube.com/watch?v=ELcza4t2BYI