Vegetable Crop Insects – April 10, 2010

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Asparagus
With the predicted warm temperatures, you can expect to see an increase in egg laying by asparagus beetles adults on spears. As a general guideline, a treatment is recommended if 2% of the spears are infested with eggs. Since adults also feed on the spears, a treatment is recommended if 5% of the plants are infested with adults. For a picture of asparagus beetle eggs, adults and larvae please refer to the following link: http://www.extension.umn.edu/distribution/horticulture/M1199.html

Cabbage
Continue to scout fields for imported cabbage worm and diamondback larvae. The first larvae can be found and sprays will be needed before they move deep into the heads. As a general guideline, a treatment is recommended if you find 5% of the plants infested with larvae. There are a number of effective materials available for worm control. Please refer to the following link for a list of materials http://ag.udel.edu/extension/vegprogram/pdf/colecrops.pdf

Melons
As soon as plants are set in the field, begin scouting for aphids, cucumber beetles and spider mites. When sampling for aphids, be sure to watch for beneficial insects as well, since they can help to crash aphid populations. As a general guideline, a treatment should be applied for aphids when 20% of the plants are infested, with at least 5 aphids per leaf, but before populations explode.

Peas
We are starting to see an increase in aphid populations. 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. When sampling dry land peas, you may want to reduce the threshold, especially if they are drought stressed. Be sure to check labels for application restrictions during bloom.

Sweet Corn
Be sure to scout the first 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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