Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Cucurbits

Beetles, squash bugs and spider mites are all active in various cucurbit crops. Cucumber beetles for the most part should be winding down until mid-July. However, care still needs to be exercised in bacterial wilt susceptible crops such as cantaloupes and cucumbers. If treating beetles with a drip application, pay special attention to label guidance on the appropriate amount of product per 1000 ft. of drip tape. This is NOT the same as a banded application to which only the protected area is used for calculating rates. Chemigating insecticides necessitates using the planted area, not the bed or plastic area to determine rates. Using bed area rates may result in a significant under application!

Squash bugs are beginning to lay eggs in fields. Consider a treatment in 1 egg mass per plant is reached AND those eggs recently or are hatching. Squash bugs are susceptible to many of the same products as cucumber beetles.

Spider mites are now detectible in most watermelon fields. So far, our scouting efforts have primarily found mites along field edges. For mites, it seems to be more of a question of when to treat rather than if. When treating, use high water rates and small droplet sizes. The key is to obtain good coverage, especially under leaves. Agri-Mek and Zeal have translaminar activity while Banter, Portal, and Oberon do not. To my knowledge, there hasn’t been any research done to determine whether or not it is better to use a miticide targeting adults or mobiles first or a miticide targeting eggs and small juveniles first. Pay attention to label guidance on bee toxicity. Labels will state that a product should not be applied to areas where bees are actively foraging or to areas where bees are foraging. The key is the word ‘active’. Such labels advise that applications be made late in the day.

Tomatoes

Scout for fruit worm damage. Earworms began flying about 2 weeks ago, though fortunately at lower levels and with apparent high moth pyrethroid susceptibility. If a worm treatment is necessary, account for other pests present such as spider mites and sink bugs. Mites can be flared, especially following stink bug applications. Thresholds are 2 mites per upper canopy leaflet. The other pest group to scout for are stink bugs. Their damage appears as white starburst type feeding scars on the fruit surface. Besides bifenthrin, foliar application of neonicotinoid insecticides can help speed mites up while pyrethroids take out all the insects feeding on mites.

Sweet Corn

Corn earworm counts are similar to slightly higher than last week. Moth susceptibility in bioassays remains high. Most parts of the state can probably get by with a 4-day spray schedule, especially following a Besiege or Elevest application. As a reminder, UD action thresholds are more conservative than neighboring states. Thursday moth trap counts are as follows: