David Owens, Extension Entomologist, owensd@udel.edu and Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu
Several fields in the SW portion of Sussex County have experienced above threshold corn earworm activity lately. I have not heard of any excessive populations or populations for which pyrethroids did not provide good control. Soybean loopers are present in many fields at low numbers, as are green cloverworm. Its important to distinguish them, cloverworms are easy to kill and are not aggressive defoliators while loopers are less susceptible to many materials. Cloverworms have a narrow body, three sets of prolegs in addition to the last abdominal segment’s prolegs. Larger larvae often have white stripes and hold their last set of prolegs out in a V shape. Cloverworms also wriggle violently when poked. Loopers tend to be narrower near the head and wider near the abdomen, and have two sets of prolegs. There are some reports of unusually high soybean aphid populations in drought stressed fields. The threshold for soybean aphid 250 per plant on 80% of plants with an increasing population. If you hit threshold, you have about a week before they might reach a damaging population. Check back in a couple of days to see if populations continue to increase, they might not if beneficials are present. Soybean aphids cause inconsistent plant injury after R5.5, and are not considered a threat once beans hit R6. Check labels for pre harvest intervals. Pyrethroids all do a good job, some have pretty long PHIs.