David Owens, Extension Entomologist, owensd@udel.edu
Alfalfa
Scout alfalfa for potato leaf hopper. Fields that have hopperburn have already lost yield potential. Cutting alfalfa will kill the majority of leafhopper nymphs, but adults will disperse. If you have multiple plantings near each other, pay special attention to non-cut plantings and be ready to treat with a pyrethroid. We have a threshold table that takes into account the value of hay, cost of control, and plant height in our Alfalfa Pest Management recommendation guide.
Soybean
Now that the earliest planted soybeans are approaching the R4 stage, pay special attention to stink bugs and corn earworm. Stink bug thresholds are 5 bugs per 15 sweeps. Corn earworm thresholds can be figured out using the NCSU earworm threshold calculator. Using some ballpark figures would put a threshold between 1.5 and 2 earworms per 15 sweep sample.
Pasture Grasses
True armyworm larvae were observed in field crop fields this week. Last year, there were reports by the end of July of armyworm stripping grass pastures. Check pastures weekly for signs of caterpillar infestation. The good news is true armyworm are relatively easy to control.