David Owens, Extension Entomologist, owensd@udel.edu
Alfalfa
Continue to scout alfalfa fields, even if they had been previously treated, for alfalfa weevil. Larvae continue hatching. As a reminder, alfalfa weevil thresholds are based on plant height, value of hay, and control costs. Our insect control guide is also based on pure stand alfalfa: https://www.udel.edu/academics/colleges/canr/cooperative-extension/sustainable-production/pest-management/commercial-field-crop-pest-management/alfalfa/. Thresholds are not applicable in mixed stands with 50% or less alfalfa.
Corn/Soybean
Now that the first field crops have gone into the soil, be mindful of slug populations. All life stages are currently active. Pennsylvania suggests a threshold of 1 per square foot under a shelter trap. I suspect this may be a bit on the low side for our area, but it underscores the importance of watching the emerging stand like a hawk. Be especially wary on no-till fields with a history of slugs and fields with brassica cover crops. For corn, we can make a rescue treatment, but be advised there are no established defoliation thresholds.
Small Grains
The first cereal leaf beetle adults have been observed in small grain in very low numbers. Aphid populations are generally low, and natural enemies are present, which should suppress their populations.