A few cotton fields have reached the point where insecticide applications can be terminated. There are reports of lingering plant bugs, increasing stink bugs, and a smattering of spider mites and bollworms in fields. This is pretty standard stuff for this time of year and should be expected in later cotton over the next couple of weeks. Below are a few points to consider.
You can ease off the gas a little on plant bug control once you reach cutout. You need to protect cotton from plant bugs for about two weeks after hitting NAWF=5 (or 250-300 DD60s). During this interval, consider relaxing your threshold from 3 to 5 bugs per drop cloth. You will need to manage stink bugs and bollworm infestations for a week or so longer (for another 100 DD60s).
Watch for bollworm infestations, particularly on WideStrike cotton. The treatment threshold is 4 or more larvae per 100 plants. On Bt cotton, we normally recommend excluding tiny, freshly hatched larvae from your counts. But finding a fair number of freshly hatched larvae should not be totally ignored. This is a good indication that some larvae will sneak past the Bt technology. At the time of year, the likelihood of bollworms or fall armyworms sneaking past the Bt technology is the primary reason I like including a pyrethroid insecticide when treating for plant bugs or stink bugs. It provides some insurance and often improves stink bug control. Perhaps my favorite combination is Orthene/Acephate at 0.67-0.75 lb/acre plus bifenthrin such as Brigade, Sniper, or Discipline at 5 oz/acre. Pyrethroids mixed with Bidrin or Transform are also good options.
Some folks have asked about using Besiege or Prevathon for bollworm control. These products are excellent but pricey. They are options that should be used on non-Bt cotton. However, I generally don’t find it necessary on Bt cotton unless bollworm pressure is unusually high. It makes more sense on WideStrike cotton, particularly if it is late maturing. There has been reports and acknowledgement by Dow AgroSciences that bollworm pressure appears to be more intense in Phytogen 333 WRF than other WideStrike varieties. So pay close attention for bollworm infestations in this variety.
Spider mite control can be tricky. Brigade or other bifenthrin products will sometimes provide some suppression … sometime not. I would suggest one of the abamectin products for more consistent control (e.g., Agri-Mek). A good starting rate is 6-8 oz/acre. NOTE: Most abamectin products are formulated at 0.15 pounds AI/gal. Agri-Mek SC is several times more concentrated, so the use rate is considerably lower. There are several good alternative miticides, but they tend to be more expensive. These include Oberon, Portal and Zeal.
