David Owens, Extension Entomologist; owensd@udel.edu
Potatoes
Colorado potato beetle adults are active and laying eggs in potato fields. Most of the insects observed this week were confined to the edge of the field, in part because beetles do not fly when temperatures are below 80 degrees. Sample a field from 10 locations. At each location, count beetle adults and larvae per stem from 1 stem on each of 5 adjacent plants. Thresholds are 50 adults, 75 large larvae, and 200 small larvae per 50 stems. There are many non-neonicotinoid options available that can be used in a rotation strategy to ease selection pressure off of neonicotinoids. They can be found here: https://cdn.extension.udel.edu/wp-content/uploads/2012/03/23152414/Potato.pdf.
Sweet Corn
Scout for cutworm injury. Thresholds are similar to field corn. Trapping data can be found here for European corn borer and corn earworm; trap data is updated by Tuesday and Friday mornings: https://agdev.anr.udel.edu/trap/trap.php.
Watermelons
Continue scouting for cucumber beetles, especially on transplant trays that are hardening off on wagons. Recent cool, wet weather has slowed beetles down, but the weather is warming back up. This year, the Extension entomology team is looking to collect several hundred beetles from individual farm sites throughout Delaware and Maryland to conduct insecticide bioassays. If you have a cucumber beetle infestation, feel free to contact me at owensd@udel.edu. We’d love to take some beetles off your hands!