Agronomic Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Corn

Continue scouting for cutworm in corn. You may see withered plants which can be indicative of cutworm, wireworm, or white grub attack. Cutworms will make burrows in the soil, such burrows will be as large as the diameter of a no.2 pencil and will have smooth sides. Heavy bird damage was reported in northern coastal fields. Bird damage (and other vertebrates) can be differentiated from cutworm by the presence of roots or the below ground portion of the plant being pulled up, the hole surrounding the seedling, seed coatings lying on the ground, and holes with flat sides. Cutworm damage is more likely in fields with weeds or green cover crop at the time of planting.

Soybean

Scout emerging soybeans carefully and regularly for slug damage. After we received a good rain 3 weeks ago, a large number of gray garden slug young juveniles became active. Fields with emerging cotyledons with more than 50% damage before unifoliates begin expanding may be at risk for stand reductions. Warm weather will help plants outgrow slug injury. If a field is tilled in any form or fashion to reduce slug activity, be sure to have an insecticide seed treatment on it to prevent our other early season pest from damaging the stand (seedcorn maggot). Bean leaf beetle may become active soon. Thresholds are pretty high, with 1-2 beetles per plant before considering a rescue treatment.

Alfalfa

If alfalfa has been cut, take a quick look at the stubble and regrowth for alfalfa weevil damage to make sure that there is not still a persistent population. Begin sweeping alfalfa for potato leaf hopper. While PLH typically arrives in mid-late May, it may be early this year due to the warm weather and mild winter.

Early Season Moth Activity

Many thanks to Haley Sater with UMD Cooperative Extension and Joanne Whalen, extension entomologist emeritus extraordinaire for assistance with checking traps.