Vegetable Insect Update – June 15, 2018

David Owens, Extension Entomologist, owensd@udel.edu and Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

Cucurbits
Squash bugs have recently become active in high tunnels, and eggs were found in watermelon this week. There are several effective products that can be used for squash bug. The broad-spectrum insecticides include neonics and pyrethroids. Neonics such as Belay, Scorpion, Venom, Assail, the group 4c insecticide sulfoxaflor (Closer) and the 4d insecticide Sivanto are also recommended for squash bug. Be mindful when using these products; all are toxic to bees. Assail and Sivanto are a little less harmful. The various products also have varying pre-harvest intervals, and rates change whether they are being applied through the drip, soil, or as a foliar application. Other products that have had efficacy in recent university tests include the ‘reduced risk’ insecticides flonicamid (Beleaf) and cyclaniprole (Harvanta), although squash bugs are not on the label.

Squash bugs prefer summer squash and pumpkin. At the end of the season, you can remove cucurbit plants and clean debris to reduce overwintering habitat. Zucchini is listed as the most susceptible type of squash. In the literature, Waltham butternut, acorn, and cushaw squash are less preferred, but I have seen large numbers build up on cushaw. Cushaws are also resistant to squash vine borer.

Helene Doughty and Tom Kuhar at Virginia Tech write in a review article (https://academic.oup.com/jipm/article/7/1/1/2658001) that wooden boards can be placed between squash rows. The bugs will hide under the boards and can be crushed easily by stepping on the board or by flipping it over and removing the insects.

Row covers can help, but because squash flowers need to be pollinated, the covers must be removed at flowering or the plants would need to be hand pollinated. Also, row covers might hurt the plants under hot humid conditions. Preliminary work in Virginia suggests that planting nasturtiums next to or in between squash rows can help repel bugs. The organic insecticides neem (azadirachtin) and pyrethrin may have efficacy on low to moderate populations.

According to degree day models, squash vine borers should be active state wide now.

Sweet Corn
As a reminder, our trapping data gets updated Mondays and Thursdays on the insect pest management Extension site, which can be accessed here: http://agdev.anr.udel.edu/trap/trap.php. We have recently seen a small bump in corn earworm activity as reported by the pheromone traps, but trap counts are declining statewide. This is normal. Historically, there is a small increase in earworm flight at the beginning of June, tapering off by the 3^rd week of June, and building again around the 2^nd to 3^rd week in July. After that, earworm activity remains pretty high through the end of the season. Historical graphs can also be found on the same site by clicking on a tab at the top of the page that says ‘historical interactive graphs’.

The spray schedule listed in the table is based off our sweet corn action thresholds which can be found here: http://extension.udel.edu/ag/insect-management/insect-trapping-program/action-thresholds-for-silk-stage-sweet-corn/.