–David Owens, Extension Entomologist, owensd@udel.edu and Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu
Continue checking fields for two spotted spider mites. Damaging hotspots have been observed in several fields. Mite associated leaf drop may look similar to general drought stress. Bean leaf beetles, Japanese beetles, green cloverworms, and grasshoppers continue to be the primary members of the defoliator complex. Other minor members present include thrips, yellow striped armyworm, bean leafrollers, and soybean leafminers. Dectes stem borers are also present, mating and doing ‘prematuration feeding.’ They will soon start laying eggs in leaf petioles. Stink bugs are moving into reproductive stage soybean fields. Stink bugs aggregate, so there may be isolated hotspots in fields. For more information on action thresholds and recommendations, please visit: http://extension.udel.edu/ag/insect-management/soybeans/.
Stressed conditions and slow canopy development set fields up for late season worm pests and also elevate the importance of defoliators. Defoliator thresholds for open canopy, late planted, and stressed beans should be 15 – 20%. I know it is a tricky balance, especially with beetle defoliators, but conserving natural enemies as much as possible is going to be important later on.