Much of our cotton fields are at or near cutout. The fields we have been in this week range from 2-6 nodes above white flower (NAWF). Keep in mind the time for a white bloom to mature into an open boll is around 50 days.
We are finding bollworms in non-Bt and 2-gene Bt cotton such as Bollgard 2 and Twin-Link cotton varieties. I have not found much damage or worms in the 3-gene cotton varieties containing the VIP gene.
While evidence of stink bug feeding has been low, we are finding brown stink bugs and eggs in soybean and cotton fields. Continue to monitor for stink bugs and treat when evidence of internal feeding on 1″-bolls exceeds 20%.
Measure NAWF by counting the number of main stem nodes above the first position white flower. The crop is usually at 8 to 9 NAWF at first bloom. This value moves lower as the season progresses. We consider the crop at Cutout when the field average is 5 NAWF.
Mark the date when the crop reaches cutout so you can determine when the field is safe from insect pests and help determine when to defoliate.
A cotton field is safe from bollworms 350 Heat Units (HU) after cutout and safe from stink bug feeding at 450 HU after cutout. We generally accumulate 22-23 HU per day during July. This means your crop is safe from bollworms and stink bugs 18-20 days after cutout.