The 2021 season may not be remembered as a severe year for stinkbugs in soybeans, but they were present in many fields. The truth is they are present in most years, usually in two major types: the green stinkbug and the brown marmorated stinkbug. Environmental conditions that affect their life cycle and whether or not you spray an insecticide can determine how many you see and how many problems you encounter.
“We definitely watch for them each year, particularly later in the season,” says Steve Gauck, a regional agronomy manager for Beck’s, based near Greensburg, Ind. “We keep an eye out for both green stinkbugs and brown marmorated stinkbugs. Both can feed on soybeans, and both can sink their mouthparts through pods into developing beans, causing that bean to typically be damaged or lost. Since they pierce the pod, they also open pods to infection by disease if weather conditions favor disease development.”
Beck’s sponsors Soybean Watch ’21.
Gauck believes adding an insecticide with the fungicides at the R3 growth stage can help control a variety of insects, including stinkbugs. However, it likely won’t control stinkbugs through the rest of the season. Continued scouting late in the season before harvest can catch possible stinkbug infestations that might warrant spraying.
According to the Purdue University Corn & Soybean Field Guide, adult green stinkbugs are bright green and shaped like a shield. Nymphs, or immature green stinkbugs, are multi-colored, wingless creatures. Finding them means adults will likely appear soon.
The best way to determine if treatment is warranted is to sweep over the top of the beans with a sweep net. Take 20 sweeps in five locations picked at random within a field. If you find 40 stinkbugs in those 100 sweeps, and soybean pods are still green, treatment is recommended. However, if you are growing soybeans for seed, the threshold is lower because quality requirements are higher. Treatment is recommended in seed fields if you find 20 adult stinkbugs in 100 sweeps with the net and pods are still green.
Brown marmorated stinkbug
The nymph and adult brown marmorated stinkbug look much more like each other than their green relatives. Nymphs may be more reddish in color, turning brown as they age. As with green stinkbug nymphs, they don’t have wings.
If you find brown stinkbugs, look for white bands on the antennae, The Purdue crop guide says that distinguishes them from other native, brown-colored stinkbugs.
The brown marmorated stinkbug is newer to the region than the green stinkbug. However, it causes similar feeding damage on pods, and has been suspected as a possible cause of delayed maturity and green stem disorder.
No threshold is established, but entomologists recommend following those for green stinkbugs.