Manage Bollworm First, but Don’t Forget Stink Bugs and Plant Bugs
As predicted, our first bollworm flight into cotton has been early and heavy. While our recommendation still stands to be prepared to use insecticides for bollworm overtop Bt cotton (click here), don’t forget that stink bugs and plant bugs will still need to be managed.
For stink bugs, a 2014 article detailing stink bug scouting and insecticide management still contains good and relevant information. Although the scouting app is no longer supported, the NC Cotton Insect Scouting Guide contains many details needed for successful scouting and management.
Note that the most effective insecticides for stink bugs are broad spectrum. This can be an advantage or a disadvantage for bollworm depending on when they are sprayed. If they are sprayed before bollworm larvae are present, they can kill natural enemies (which seem abundant this year, perhaps because of the widespread low levels of aphids) and release bollworm into the system. For example, I often use Orthene to flare bollworm levels by spraying before a flight. However, many of these insecticides can boost bollworm control when they are sprayed when bollworm larvae are established. Bidrin, while a great stink bug and plant bug insecticide, will do little to control bollworm.
Plant bugs, while present in relatively low numbers this year, are building in cotton. Nymphs just started to show last week (middle of July) in many fields. Now would be a good time to mix Diamond with a pyrethroid. This combination should provide knock down of the adults and extended control of the immatures. When cotton is blooming, square retention is a less reliable measurement of plant bug activity. Switch out sweep net sampling for drop cloth sampling in blooming cotton. More and relevant information can be found in this 2016 article.