David Owens, Extension Entomologist, owensd@udel.edu and Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu
The usual defoliators are present in fields, albeit in low numbers this week. We are finding green cloverworms, bean leafrollers, grasshoppers, an occasional bean leaf beetle, thrips, Japanese beetles, and spider mites. First generation bean leaf beetle populations are dwindling, the second generation should emerge from the soil in late July – August.
Two spotted spider mites are showing up in more soybean fields. Mite populations are still low enough to warrant continued monitoring. With hot dry weather (didn’t think I would be saying that), populations can increase rapidly. As a reminder, most pyrethroids tend to ‘flare’ mites by removing natural enemies, although bifenthrin does have activity on TSSM. Zeal and Agri-mek are two other very effective, narrow spectrum products that have excellent spider mite activity. You can find our action thresholds and insecticide recommendations here: http://extension.udel.edu/ag/insect-management/soybeans/. In R-stage soybean, we are also picking up green stink bug adults, egg masses, and first instar nymphs. We picked up our first Dectes stem borer yesterday in a corn field that was soybean last season, emerging from its overwintering chamber in the soybean stubble.