David Owens, Extension Entomologist, owensd@udel.edu
Sorghum
Continue scouting for sugarcane aphid. Thresholds are 30% infested plants with localized areas of honeydew/established aphid colonies. The only recommended materials are Sivanto and Transform.
Soybeans
A smattering of various pests continues to be reported, the most common are stink bugs, earworms, and loopers. Dominic Reisig at NCSU wrote an excellent article on soybean looper: https://soybeans.ces.ncsu.edu/2023/02/why-soybean-loopers-are-frustrating-to-control-and-what-we-are-doing-about-it/. The gist of the article is that defoliation thresholds are conservative. Defoliation at R6 is less likely to impact yield than at R4 or R5. In previous years, he has commented that 1 per sweep is a concerning number. Nighttime temperatures in the 50’s may suppress looper activity.
Soybeans are most susceptible to stink bug damage in the R5 stage – beginning seed formation. Thresholds are 4-5 bugs/15 sweeps. If a field is at or over threshold and brown stink bugs or brown marmorated stink bugs are present, the best two materials are bifenthrin and acephate (Orthene). Once we move into the later R6 stage when the seeds begin to separate from each other in the pod, stink bugs become less of a yield threat and more of a quality threat. When pods begin turning yellow and leaf senescence begins, thresholds increase.