David Owens, Extension Entomologist, owensd@udel.edu
Soybean
Japanese beetle and Asiatic Garden beetle are active, as are the remaining usual defoliators. Dectes stem borer is beginning to emerge out of the soil; emergence typically peaks around mid-July. I have seen it most common in full season beans that are flowering. Dectes love sunflowers, if soybeans are planted near previous year’s dove hunting plots or seed plots, scout for Dectes and prioritize early harvest.
Spider mites are beginning to show up along field edges. Stippling will not be as obvious with off-colored drought stressed upturned leaves. To scout for mites, determine the extent of the infestation and assess the level of injury by examining 20 to 30 plants in the infested area. If isolated spots of mite activity are confined to the perimeter of the field, spot-treatment using ground equipment is recommended to prevent further spread of mites into the field. If the infestation is distributed throughout the interior of the field, treatment of the entire field is suggested. If live mites are numerous (20 or more per leaflet), and more than 50 percent of the plants show stippling, yellowing, or defoliation over more than one-third of the leaves. It may be tempting to not invest in drought stressed soybeans, but it is precisely under these conditions in which defoliation will have a greater potential impact on yield because the plants are less able to compensate for defoliation should they get a rain. The best materials for mites in soybean by far are Agri-Mek and Zeal.
Stink bugs are active in R-stage beans; thresholds are 5 bugs per 15 sweeps but, for a year like this one if beans are growing slowly or are drought stressed, you may want to consider lowering that threshold.
Corn
Continue scouting for stink bugs in early tassel push corn. The majority of stink bugs can be found on the stem around the area of the developing ear. If more than 10 stink bugs are found on 100 plants, treat the field. Of the pyrethroids, bifenthrin has the most activity on brown stink bugs. Stink bugs are most damaging prior to silk emergence.
Vantacor Label Update for Sorghum
Vantacor (Chlorantraniliprole) has an updated label rate recommendation for SORGHUM: 0.9 fl oz/acre for headworms.