As we enter the boll formation phase of the crop, one insect pest I have been picking up quite consistently is the Conchuela stink bug. It is a relatively large insect (~1/2 inch long) with a distinctive dark olive green to black coloration and a reddish margin around the body. Their populations develop on mesquite trees and various weedy hosts, and as the quality of these host plants declines, they migrate into grain crops and cotton.
These stink bugs are voracious feeders and can be found in multiple numbers on the same boll (picture below). Stink bugs in general prefer to feed on medium-sized bolls, approximately the size of a quarter-dollar coin. Feeding on young bolls (<10 days old) often leads to boll shedding, while in larger bolls, stink bug feeding results in the formation of dark spots on the exterior. These dark spots do not always correspond to internal damage, which is why the newer stink bug thresholds are based on internal boll damage.
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Dynamic boll injury threshold for stink bugs |
The most effective insecticide products for stink bugs are either pyrethroids (e.g. bifenthrin, lambda-cyhalothrin) or organophosphates (e.g. acephate, Bidrin). These chemistries are much harsher on beneficials compared to some of the softer products used for aphids and plant bug control. Therefore, I would avoid rushing into an entire-field application unless stink bug numbers or internal boll injury justify the treatment. Neonicotinoids, such as imidacloprid can offer some level of stink bug suppression, but products commonly used for cotton fleahopper, aphid, or plant bug control (e.g. Carbine, Sivanto, or Transform) will not provide stink bug control.
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Conchuela stink bug adults on cotton boll |