Vegetable Crop Insects

Joanne Whalen, Extension IPM Specialist;

Fields should be scouted for imported cabbage worm and diamondback larvae. We are starting to see an increase in moth egg laying activity. As a general guideline, a treatment is recommended if you find 5% of the plants infested with larvae. If both insect species are present, Avaunt, the Bt insecticides, Proclaim, Rimon, Spintor or Radiant have provided control.

As soon as plants are set in the field, you should begin scouting for cucumber beetles, aphids and spider mites. Aphids can be found in the earliest transplanted fields. When sampling for aphids, be sure to watch for beneficial insects as well since they can help to crash populations. As a general guideline, a treatment should be applied for aphids when 20 percent of the plants are infested with at least 5 aphids per leaf. Foliar treatments labeled for melon aphid control on melons include Actara, Beleaf, Fulfill, Lannate and Thionex. These materials should be applied before aphid populations explode. The Fulfill label states that the addition of a penetrating type spray adjuvant is recommended to provide optimum coverage and penetration. Admire, Platinum and Venom are also labeled at-planting for aphid control.

We are starting to see an increase in aphid populations on peas so be sure to sample all fields on a weekly basis. On small plants, you should sample for aphids by counting the number of aphids on 10 plants in 10 locations throughout a field. On larger plants, take 10 sweeps in 10 locations. As a general guideline, a treatment is recommended if you find 5-10 aphids per plant or 50 or more aphids per sweep. Be sure to check labels for application restrictions during bloom.

Begin sampling the earliest planted and emerged fields for Colorado potato beetle adults, especially if an at-planting material was not used. Low levels of the first emerged adults can now be found. A treatment should not be needed for adults until you find 25 beetles per 50 plants and defoliation has reached the 10% level.

Sweet Corn
Be sure to scout emerged fields for cutworms and flea beetles. As a general guideline, treatments should be applied for cutworms if you find 3% cut plants or 10% leaf feeding. In order to get an accurate estimate of flea beetle populations, fields should be scouted midday when beetles are active. A treatment will be needed if 5% of the plants are infested with beetles.

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