Vegetable Crop Insect Scouting

David Owens, Extension Entomologist; owensd@udel.edu

Sweet Corn
This is about the time of the year that fall armyworm may start paying us a visit. Be on the lookout for whorl damage. Treatment thresholds are 12-15% infested plants. Good armyworm products include methomyl, though it doesn’t have residual activity (Lannate), diamides (Coragen), methoxyfenozide when worms are small (Intrepid), indoxacarb up till tassel push (Avaunt) and spinosyn class insecticides (Radiant, Entrust). Pyrethroids generally do not do as well on fall armyworm, in part because worms feed deep in the whorl where adequate coverage and contact is difficult to achieve.

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 have come up a lot over the last week. In addition, we were able to test 24 moths this past week with 19% survivorship. This is still lower than last year at this time, but greater than June’s moth survivorship. With the warm weather and elevated trap captures and rising potential resistance, shorter spray schedules than on our webpage would be advised. Thursday’s trap capture is as follows:

Watermelons
Weather conditions are conducive to rapid mite population build up. Also, be on the lookout for first generation cucumber beetles and worms. If worms are present, pyrethroids may help knock them down, but there are better options, including the diamides Coragen, and Harvanta, the spinosyns including Radiant, Bt, and Intrepid.