Vegetable Crop Insect Scouting

David Owens, Extension Entomologist; owensd@udel.edu

Watermelon
Spider mite populations continue to build up near the edges of fields. In general, very few are in the main crop, but there are some exceptions. Last year and this year, pokeweed along wooded edges has been the first plant to become heavily infested (see picture below, note the yellow and reddening leaves caused by heavy mite loads).

Complicating the picture a little bit is the arrival of worms in several fields. We observed 2^nd instar caterpillars of various species in melons this week. To my knowledge, beet armyworm has not yet been observed in pigweed or main crops. Most other worms should be fairly easy to control with most products. Radiant, a good worm product, does have some effect on spider mites though not as good as a miticide. Some premix products are available, including Minecto Pro (Abamectin + cyantraniliprole) and Gladiator (avermectin B1 + zeta-cypermethrin). Be sure to follow label directives regarding pollinator protection and use of adjuvants if using either product. The cyantraniliprole is a systemic material with long residual control of Lepidoptera.

Sweet Corn
Sweet corn pheromone and blacklight traps are checked twice weekly on Mondays and Thursdays. By Tuesday and Friday morning, data is uploaded to our website: https://agdev.anr.udel.edu/trap/trap.php. For reference, action thresholds based off of blacklight and pheromone trap can be found here: http://extension.udel.edu/ag/insect-management/insect-trapping-program/action-thresholds-for-silk-stage-sweet-corn/. Moth counts continue to decrease. We have caught very few moths in our pheromone traps at the REC, and moths are no longer looking ‘fresh’. We have been evaluating moth susceptibility to pyrethroids using vial testing (vials prepared by Dr. Sally Taylor’s lab, Virginia Tech Tidewater AREC). So far, we have run 69 treated moths and have not observed elevated levels of resistance. I suspect this will change later in the season when southern migrants reach our area. Last year when we started, about 20% of moths survived the treatment in late June to early July, but by the end of August, around 40% survived. Thursday’s trap capture is as follows: