LESREC Cucumber Beetle Pest Management Trials 2022
David Owens, University of Delaware Extension Specialist, Agricultural Entomology
owensd@udel.edu; 302 698-7125
Cucumber beetles are one of the key insect pests affecting watermelon, cantaloupe, cucumber, squash, and pumpkins throughout the country. They transmit diseases such as bacterial wilt to many (watermelons are resistant to wilt), and they feed on rinds which can render the fruit unmarketable. Insect pest management for cucumber beetles involves regular early season scouting and early to mid-summer scouting. Usually around Memorial Day, cucumber beetles migrate into fields. Early colonizing males release aggregation pheromones which act as a beacon to bring a greater population into the field. Females lay eggs in the soil and by mid-July, first generation adults emerge out of the soil to feed on flowers, leaves, and fruit. Cucumber beetle management relies heavily upon neonicotinoid insecticides in drip lines (ex. Admire Pro, Platinum) or broadcast insecticides (ex. the neonicotinoid Assail, pyrethroids, and the diamide Harvanta). A trial performed at LESREC in 2021 indicated reduced susceptibility to the pyrethroid class of chemistry, severely limiting pest management options. In 2022, a follow-up watermelon trial was planted at LESREC to evaluate these insecticides. Plots consisted of 3 rows, 10 plants each of ‘Fascination’ seedless melons transplanted May 25. Overwintered beetles were treated on June 24 with Admire Pro and Platinum in the driplines and foliar Brigade and Azera. Treatments were replicated three times. We produced a video discussing the proper way to calculate product rates when chemigating fields with insecticides and that was posted to YouTube.
Overall beetle numbers were low in 2022 and no significant treatment differences were observed for applications targeting the overwintered generation. A second application was made in August, with treatments applied August 2, 9, and 19, testing an experimental product from Syngenta and comparing it with another insecticide Besiege. (Besiege is a pyrethroid/ diamide premix sometimes used for rindworm management). Summer beetle pressure was also low, and no significant treatment differences could be detected in terms of live or dead beetle counts and incidence of flower feeding. While it was disappointing not be able to follow up on interesting findings from the 2021 trial year, there were multiple trials conducted in Maryland and Delaware in which beetle pressure was unusually low. More trial work is being conducted in 2023 at LESREC and at the University of Delaware Carvel REC. We are grateful to the University of Maryland experiment station for supporting work to understand how beetle susceptibility to commonly used insecticides may be changing as well as gathering data on potential new products. We also are grateful to David Armentrout for his support and assistance with this project.