David Owens, Extension Entomologist, owensd@udel.edu
Soybean
Reports are starting to come in of threshold levels of corn earworm in soybean. As a reminder, NCSU has a good earworm threshold calculator: https://www.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html. Moths were active last week in fields with flowers, and worms are being found in fields as late as R4.5. If using a pyrethroid, use the highest label rate, as good control is not guaranteed. The product Hero, when used at its high rate, is essentially a mix of two pyrethroids at their individual high rates. Our control recommendation guide can be found here: https://www.udel.edu/content/dam/udelImages/canr/pdfs/extension/sustainable-agriculture/pest-management/Insect_Control_in_Soybeans_-_2020_-_David_Owens.pdf. When scouting and selecting insecticides, pay careful attention to the green worm complex. Soybean loopers are present in the area at low populations but can be flared up with pyrethroid and organophosphate use.
Sorghum
Sugarcane aphids are present in the region but so far are still spotty. Although I am optimistic that it has arrived late enough in the season and that forecast cooler weather will slow them down, it is still important to regularly scout for them. In hot weather, their reproductive rate is phenomenally fast. They can cause yield loss to drought stressed sorghum as late as the soft dough stage. Thresholds are generally between 40 and 125 per leaf, or 30% infested plants with localized areas with honeydew present. The only effective insecticides are Sefina, Sivanto, and Transform. Lorsban and Dimethoate suppress them for only a short period of time.
Last week, corn earworm were observed resting and flying in sorghum heads. Be sure to scout for earworm in all sorghum fields that are or were recently shedding pollen. Texas A&M has an excellent threshold calculator and earworm size guidance here: https://extensionentomology.tamu.edu/sorghum-headworm-calculator/.
Hemp
Scout buds carefully for early instar corn earworm. Second instars generally are an orangish color with black near the hair bases, and the raised tubercles with microspines give them a slightly bumpy appearance. If treatments have not yet started, they will probably be necessary this week. The best products in Virginia Tech trials have been virus products followed by Bt. Use high water rates to achieve good coverage.