Worms are different this year, or maybe it is the first medium to heavy moth flight we have seen in a while. Another difference is less cutout cotton than normal.
Whatever the case is, I am finding live worms in cotton fields since last week that I have not seen during the modern error of cotton production. Let me quickly add, that many of our fields look like they always do. I think it could be a little bit of a perfect storm where multiple things had to get together to result in larger worms getting by our typical system of waiting to the third week of bloom to spray a high rate of a pyrethroid. (Which I think has always worked well during this decade.)
The first factor is the variety. 333 and 312 uniquely have been the varieties I am finding the most escape worms following a pyrethroid spray. 499 to a lesser extent, even less in 444 and very little in Widestrike 3, Twin Link in Stoneville and Boll Guard.
The second factor is the moth flight intensity. In addition to being 333 or 312, the fields with more worms has been related to a high flight. Some areas have not experienced as many moths and egg laying.
The third factor is the effectiveness of pyrethroids on corn earworm. Resistance has been an issue for several years though and although it seems to be a bit higher, there also seems to be a correlation to early application. Sort of like which came first the chicken or the egg. If the pyrethroid was applied before the eggs hatch, it seems to work better.
A final factor is having a young crop with a lot of small bolls and blooms still going on.
In Summary: If you have 333, 312, 499, or perhaps 444 that is still blooming and setting bolls, then I believe an automatic respray this week (if you have not done it yet) is the best course of action. If you have had an extremely heavy moth flight, crazy high numbers of worms in nearby bean fields, or if the worms were already present when you sprayed the first time then it is likely you have larger worms escaped. The good news is that if you have some escapes — Belt, Besiege or Prevathon are very good at cleaning them up.