David Owens, Extension Entomologist, owensd@udel.edu
Alfalfa
Potato leafhopper are active in alfalfa fields. Pay special attention to short fields after a more mature crop has been cut. The cutting process kills many leafhopper nymphs and adults, those adults that survive disperse away. If there are multiple plantings near each other, it could lead to an increase in the later fields. Similar to alfalfa weevil, there is a dynamic potato leafhopper threshold depending on cost of control, forage value, and plant height. Recommendations can be found at the bottom of the field crops extension page: https://www.udel.edu/academics/colleges/canr/cooperative-extension/sustainable-production/pest-management/commercial-field-crop-pest-management/.
Corn
Continue scouting corn for stand loss due to cutworms. The threshold for cutworm is 2-5% cut plants up to the V5 stage and with active larvae present.
Soybean
Scout soybeans for defoliation and with recent rains and cooler weather, slug injury on seedlings. Defoliation thresholds are close to 40%. A few cutworm have also been found in fields, so make sure that stand is not being harmed.