Japanese beetles, green cloverworm, bean leafrollers, and grasshoppers are the primary defoliators that we have seen in soybean samples. Bean leaf beetles are also starting to make a reappearance. Thresholds for pre-bloom full season beans is 30% and threshold for reproductive stage soybean is 15%. Double crop fields, especially dry fields, cannot tolerate as much leaf feeding as their full season counterparts.
Dectes stem borer continues to emerge from nearby overwintering sites in last year’s soybean stubble. You can find more information about Dectes stem borer in our fact sheet: http://extension.udel.edu/factsheets/dectes-stem-borer-management-in-soybeans/. Two-spotted spider mites also continue to move into fields, most in low numbers but with warm dry weather, a low number of mites can become a large number of mites in a short period of time. Thrips are also widespread, and abundant in hotspots in some fields. Treatment thresholds for thrips might be triggered if there are more than 8 thrips per leaflet, the beans are drought stressed, and visible ‘cupping’ or distortion is occurring.
Green stink bugs are present in reproductive stage soybean. Feeding is a concern for beans in the beginning pod to filled pod stages. Our general threshold for grain soybean is 5 bugs per 15 sweeps.