By Adam Varenhorst, Extension Field Crop Entomologist
While looking at winter wheat at the new SDSU West River Research Farm near Sturgis, S.D. we came across some very large stinkbug populations in a few areas of the field (Figure 1). The stinkbugs we observed were the Say’s stinkbugs.
Although stinkbugs have the potential to reduce wheat yields, this is attributed with feeding that occurs between the late boot and milk stage. After the milk stage, the impact that stinkbugs have on wheat is greatly reduced. However, historical evidence indicates that very large populations feeding during the dough stage can reduce harvested test weight.
Say’s stinkbug feeding on developing grain can also result in shriveled and deformed kernels. Most of the winter wheat is past the milk stage, but spring wheat should be monitored for Say’s stinkbug populations. These particular stinkbugs feed on other hosts, including Russian thistle, before moving to the grain during heading and grain fill.
Identification and Management
Say’s stinkbugs are large and green. They have a yellow-orange band that goes around the edge of their body. In addition, they have three white spots in the middle of their body and one orange spot below those (Figure 2).
The threshold for Say’s stinkbugs is three to four per 100 sweeps using a 15-inch diameter sweep net when wheat is between the boot stage and milk stage.
If management is necessary, please refer to the 2019 South Dakota Pest Management Guide: Wheat.