Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Tomato

Continue treating for tomato fruitworm. Moth flight has been heavy. Also look for the characteristic yellow starburst pattern of stink bug feeding on the fruit. Excellent stink bug products include Assail and Venom or Scorpion, but these will not protect from worms. Spider mites continue to be active. Scout for mites by examining upper terminal leaflets. Treatment is generally advised when mite counts exceed 4 per leaflet.

Cole Crops

We transplanted our cabbage Lep trial this past week and had cabbage whites oviposit on them as soon as the transplants were in the ground. All other cabbage pests are active. Thresholds for early transplants are 20% infested plants early, rising to 30% until early cupping. Harlequin bugs are also active and may require treatment. Neonicotinoids will provide excellent control without destroying the natural enemy complex, but will not provide worm control alone. Two premixes that contain both a neonic and a dimaide are Durivo and Voliam Flexi. Be sure to factor the diamide into your rotation scheme.

Squash

For those of our readers who are in Virginia, southern Maryland, or on the southern eastern shore, be careful to scout for pickleworm. The following is taken from Virginia Tech’s Ag Pest Advisory post by Dr. Lorena Lopez stationed at the Eastern Shore AREC in Painter from August 26:

“Both melonworms and pickleworms have been detected in squash plantings yesterday in Cape Charles and Machipongo farms. Approximately, 80% of the plants showed at least one flower bud/fruit with borrowing injuries. Most of the squash fruit and flower buds contained 1-2 melonworms in the latest stages of their larval development (4th-5th instar). Pickleworms on the other hand, have just started to show up in the area and only 1st to 3rd larval instars were found, most of them on top of flower buds and growing fruit. Both pests were also detected in one cucumber planting on approximately 30% of the plants sampled. These pests have been detected in squash plantings in Blacksburg this week at a lower infestation rate compared to the Eastern Shore.

Well-timed insecticide applications are crucial for the management of these pests and recently hatched caterpillars that haven’t borrowed into the plant tissue are more susceptible to insecticides. However, once they borrow inside fruits and flower buds, contact insecticides are usually not enough to suppress these pests. The use of systemic insecticides is preferred.

Useful tip: Pickleworms and melonworms are NOT the same as squash vine borers. Squash vine borers borrow into the stems causing severe damage and eventually plant death, unlike pickleworms and melonworms that feed mostly on the reproductive parts of the plant and occasionally the leaves.

If you find borrowing damage in cucurbit crops on your respective farm or gardens, please contact me at lorelopezq257@vt.edu.”

Sweet Corn

Trap counts remain elevated across the trap network, with most sites indicating a 2-3 day spray schedule. Guidance is essentially unchanged from last week, high temperatures for the next several days dictate a tighter spray schedule on account of moth eggs requiring less time to hatch. Concentrate sprays around the first 10 days of silking. Trap counts from Thursday are as follows: