All the cotton I’ve looked at this week is past cutout (5 nodes above white flower) and a good number of fields have open bolls. I’ve been seeing the bollworm (H. zea, corn ear worm, etc.) egg lay decreasing, and most of the larvae are cycling out.
Last week I spent a good deal of time collecting bollworms out of double traited and one vip traited field. Those bollworms have been sent to the lab in College Station for Bt resistance testing.
In places still susceptible to bollworms, it’s important to be checking for them even if you have Bt cotton. There is no threshold set for egg lay (since they have to feed for Bt to effect them and many other insects consume eggs), but our adapted threshold for caterpillars after last year is 6% damaged bolls or squares with live caterpillars present.
When cotton reaches cutout (5 NAWF), it has 350 heat units remaining before the bollworms can no longer cause yield loss.
In the places that are still susceptible to stink bugs, the threshold for stink bugs is 20% of bolls damaged with stink bugs present. Once cotton has reached 450 heat units past cutout, treatment for stink bugs may no longer be necessary, as the bolls they can still feed on will not mature in time to contribute to the overall yield.
Fields that experienced drought stress this year may have a longer time frame for yield loss to occur, and stink bugs may still need to be a consideration until 450 heat units past 3 or 4 NAWF.