by David Kerns, Professor & IPM Coordinator
In cotton we have been seeing a great deal of bollworms activity in Bt cotton and there have been quite a few insecticide applications going out. A lot of these reports have been coming out of the Wharton and Corpus Christi areas, but it is not confined to just those locations. In the Brazos River Bottom, we had a field of WideStrike cotton that virtually had a worm in every terminal and as much as 40% fruit loss in the upper third of the canopy. We have reports of unacceptable injury in some TwinLink and Bollgard 2 as well. Thus far I have not heard of any problems with WideStrike 3 or TwinLink Plus. We have collected several populations from WideStrike and TwinLink that we will evaluated for resistance to the Bt toxin. If you have a Bt field with unacceptable bollworm injury, please let me know; we would like to make more collections. Be sure to give the technology the opportunity to work. Our research has shown that if you are running 6% injured fruit with live larvae present, it pays to spray. This being said, if I have a very large egg lay in WideStrike technology, I would be inclined to spray. Make sure you check blooms, bracts and bloom tags for eggs and small larvae. I great many of the eggs lays we are seeing are not so much in the terminal but in the canopy. Most common insecticide choices are pyrethroids, Blackhawk (3.2 oz/ac), Prevathon (14-19 fl-oz/ac) and Besiege (7-10 fl-oz/ac). Be careful with the pyrethroids. Granted they are inexpensive, but we have had some reports of control failures, especially if the worms are second instar or larger. In a grain sorghum test I just completed on bollworms, lambda-cyhalothrin did not differ for the check after 7 days, but this milo had quite a few large worms. Residual with pyrethroids is only about 5 days and they tend to flare aphids and mites. Blackhawk is efficacious but will only provide about 5 day control as well. Prevathon and Besiege will tend to last much longer; I have seen them provide protection for 21 days. Besiege has the same active ingredient as Prevathon but also includes a pyrethroid. If you have a few stinkbugs in your cotton the Besiege might be a good option, but if you have a lot of stink bugs, I suggest spiking it with a little more lambda-cyhalothrin.
As mentioned, bollworms have also been in the milo and if you catch them small (1st – 2nd instar), pyrethroids usually do fine, but rely on Blackhawk, Prevathon or Besiege if very many large worms are encountered. In milo we can usually get by with lower rates of these products than we can in cotton. Sugarcane aphids have been spotty, but I expect populations to take off if the hot dry conditions continue. I prefer to treat when 22-25% of the plants check have colonies of 50 or more aphids, more can be tolerated once you get to soft dough stage. Products of choice for sugarcane aphid are Sivanto Prime at 4 fl-oz/ac or Transform at 1 oz/ac. Both are efficacious, but Sivanto will provide longer residual control. Additionally, if the aphid population is high, I suggest Sivanto Prime.
In soybeans stinkbugs continue to be a source of problems in some areas. Green stinkbugs are easily controlled with acephate or pyrethroids, if you have brown stinkbugs lean more on acephate, they tend to be harder to control with pyrethroids. If you have red banded stinkbug, stick with acephate at 0.75-1.0 lbs/ac or Bifenthrin at 6.4 fl-oz/ac. Also keep in mind that red banded stinkbug and injury bean pods to almost R8.
Feel free to contact me if you have any questions.
Professor & IPM Extension Specialist
Texas A&M AgriLife Extension Service
Department of Entomology
College Station, TX 77843-2475
dlkerns@tamu.edu
979.845.2516