David Owens, Extension Entomologist, owensd@udel.edu
Corn
Continue scouting for stink bug in late corn and for western corn rootworm in fields that were in corn last year (and even more so for fields that have been in continuous corn for multiple years) AND will be in corn next year. Thresholds for soil insecticide or a rootworm Bt trait are 1 WCR per plant. Targeting adults is not recommended. Stink bug thresholds increase after VT stage.
Soybean
Scout for mites, defoliators, and stink bugs. Mite thresholds are based in part on plants being drought stressed, stippling on 20-30% of leaf area and mite populations actively growing. Fungal pathogens are present in the area, so check mites to make sure they are in fact alive. Dead mites will have a brown, fuzzy or shrunken appearance. The best and most consistent miticides have been Agri-mek and Zeal. Dimethoate has some decent mite activity, equivalent to Lorsban. It can reduce mite populations enough to reduce their impact on yield but it will not eliminate them. Dimethaote is also excellent on grasshoppers. Stink bugs are also very active this season. I recently recorded a pest patrol update about them. Pest patrol is a free text service that notifies subscribers when a regional update has been recorded. Thresholds are 5 bugs per 15 sweeps, but I suspect it should be a bit lower in Plenish soybean. Stink bugs will not cause any yield impact until R4 – full pod stage, and the greatest yield impact at R5, beginning seed stage. However, stink bugs present at R2 or R3 have very little reason to leave the crop, except through natural mortality.
My IPM App
A handy smartphone app was developed by Clemson and the Southeatstern IPM Center that can be downloaded and accessed offline. There are downloads available for sorghum, corn, and soybean. There is information on chemical control, monitoring, scouting, thresholds, and identification. Check it out.