South Carolina Cotton: Remain Alert For Bollworms But Add Stink Bugs To Your List

Photo: Mississippi State University

Captures of bollworm moths in pheromone traps have increased dramatically, as have sightings of adults and larvae in the field. We are finding much more injury to non-Bt cotton than we observed last year.

Most of the 2- and 3-gene Bt cotton is holding up well under the pressure, but we are still seeing a few terminals, squares, blooms and bolls injured here and there.

Scout for eggs and larvae, and pay particular attention to blooms. Any counts over 20 eggs per 100 plants should get your attention. When those eggs hatch, you want to catch those larvae when they are small and exposed. Most will succumb to Bt toxins as neonates. But if they make it to second or third instars, Bt cotton is not going to kill them.

If a moth puts an egg on a bloom, it is almost impossible to see, but look for small larvae in white blooms. You can catch them there when they are small. When blooms dry into what we call a dried bloom tags, look under tags on the tops of small bolls for small larvae burrowing into bolls.

It is difficult to control bollworm with any foliar insecticide when much of this is occurring, so you have to get in front of them some by catching the flight early.

Pay attention to moth activity in the field, look for eggs and small caterpillars, and be timely with any sprays. That’s what should be done.

Now, Focus On Stink bugs

Stink bugs should be the focus of insect management efforts in cotton from here to the end of the season – well, at least to the seventh week of bloom. Do you know what week of bloom your fields are in right now? I hope so.

Proper use of our dynamic boll-injury threshold requires you to know what week of bloom you are in for each field. You have to know that to control stink bugs effectively using the threshold. The first week of bloom is when every other plant has its initial white flower.

This occurs shortly after you notice the first bloom in the field. Most of our cotton is past this event, but, generally, cotton starts blooming about 60 days after planting.




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