David Owens, Extension Entomologist, owensd@udel.edu
Soybean
Continue scouting R3-R5 soybean for stink bug. Thresholds are 5 bugs in 15 sweeps for conventional beans, 2-2.5 bugs for seed production, and somewhere in between is where Plenish soybeans should be at.
Defoliation appears to be fairly minor this year. If going across the field with a fungicide, I strongly recommend not including an insecticide at this time unless scouting indicates a pod feeding insect population is present (stink bug, CEW, large numbers of bean leaf beetle). Our earworm flight still has time to come in and the last thing we need to do is to destroy natural enemies because of a convenience application of a short-lived product. This can set a field up for both earworm and looper later on.
Start scouting for corn earworm in flowering to R4 beans. NCSU has a good threshold calculator here: https://www.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html.
Sorghum
Scout sorghum about a week after pollen shed for headworms. As a general rule, 1 larger CEW/head can cause up to a 5% yield loss. Texas A&M has a great threshold calculator for sorghum here: https://extensionentomology.tamu.edu/sorghum-headworm-calculator/. Please note that mortality in small worms in sorghum can be quite high.
We found our first sugarcane aphid (now sorghum aphid) this past week in Georgetown plots. This aphid reproduces rapidly. It colonizes lower to mid canopy leaves first. Do not confuse this with corn leaf aphid which is green. I generally think of corn leaf aphids as almost beneficial in sorghum for jumpstarting aphid predators. Typically, CLA populations crash once the head emerges. There is limited advice on insecticide efficacy for CLA in sorghum.
The threshold for Sorghum or Sugarcane aphid in susceptible varieties is 30% infested plants with localized areas of honeydew and established aphid colonies. Check mid canopy leaves. Pyrethroids are DO NOT work on them. Check with your local seed dealer if your variety has known tolerance or resistance to sugarcane aphid, as thresholds are higher.