David Owens, Extension Entomologist, owensd@udel.edu
Alfalfa
Potato Leafhopper is active in our area. If you have cut alfalfa and it is growing, begin scouting for PLH. There are leafhopper resistant varieties that are a bit hairier than standard varieties. There are also varieties that do not yellow but will still suffer a yield hit by PLH. Our alfalfa recommendations page has a dynamic threshold for PLH based on plant size, control costs, and hay value: https://www.udel.edu/content/dam/udelImages/canr/pdfs/extension/sustainable-agriculture/pest-management/Insect_Control_in_Alfalfa_-2020_-_David_Owens.pdf.
Corn
Slugs continue to be a significant defoliator, especially on late planted corn.
Monitor also for cutworm damage. There are scattered reports all across the Delmarva of significant cutworm damage requiring follow up applications. The threshold is 2-5% cut plants depending on the size of the larvae and plant stage. If a field is over threshold, there are several pyrethroids labeled for cutworm. We have also just released a short extension video discussing how to identify early season pest damage. Check it out at https://youtu.be/D4wJwUEmlEI . Many thanks to Morgan Malone and Michele Walfred. Two critters that we did not discuss in the video are thrips and stink bugs. Thrips feeding looks like fine silvery lines or strips on the leaf blade. Thrips are not known to impact yield. Stink bugs however can. Their feeding will look like several rows of jagged holes (not perfectly round holes). The leaf blade will yellow above them and heavily impacted plants will tiller at the base. NC has developed thresholds for stink bugs in corn: https://entomology.ces.ncsu.edu/2018/04/new-stink-bug-thresholds-in-corn/
Soybean
Continue evaluating stands for signs of cutworm and slugs. There have been report of cutworm flight being a bit earlier year. There has also been a hatch of grasshopper eggs. Among the defoliator complex, grasshoppers and worms are active.
Small Grains
I have not received any reports of significant armyworm populations or head clipping in small grains, but please remember that our traps did catch a heavy armyworm flight in the Harrington and Smyrna areas.
University of Kentucky entomologist Raul Villanueva and ag engineer Sam McNeill recently wrote an excellent checklist for preventing stored product pests from getting into wheat in storage. You can find their excellent and timely article at:
There are links for control fact sheets as well.