Vegetable Crop Insects – May 17, 2013

Joanne Whalen, Extension IPM Specialist;

Be sure to scout all melons for aphids, cucumber beetles, and spider mites. We are seeing high levels of lady beetles in some fields that are helping to keep aphid populations in check. The first cucumber beetles are starting to be found in the earliest planted cantaloupe fields. As soon as we get a few consecutive days of warm, sunny weather, populations can explode so be sure to scout carefully since damage occurs quickly. Since beetles can continue to re-infest fields as well as hide under the plastic, multiple applications are often needed to achieve control.

Be sure to sample any early planted fields for thrips and corn borers. We are finding the first corn borers in light traps; however, the populations remain low. On young plants, corn borer larvae can bore into the stems and petioles. In areas where peppers are isolated or corn is growing slowly, moths are often attracted to young pepper plants. Therefore, you should watch for corn borer moths laying eggs in all fields. As a general guideline, treatment may be needed if there is no corn in the area or you are using rye strips as windbreaks. You should also look for egg masses on the leaves. For the most recent trap catches, you can check our website at ( or call the Crop Pest Hotline (in state: 800-345-7544; out of state: 302-831-8851).

Snap Beans
Continue to sample all seedling stage fields for leafhopper and thrips activity. The thrips threshold is 5-6 per leaflet and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by 1/3. In addition, bean leaf damage is showing up in early planted fields so be sure to watch for adult beetles. Damage appears as circular holes in leaves and significant defoliation can quickly occur. As a general guideline, a treatment should be considered if defoliation exceeds 20% prebloom.

Sweet Corn
Continue to sample for cutworms and flea beetles. As a general guideline, treatments should be applied 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 mid-day when beetles are active. A treatment will be needed if 5% of the plants are infested with beetles. Watch for small corn borer larvae in the whorls of the earliest planted fields, especially fields that were planted under plastic. A treatment should be applied if 15% of the plants are infested. Low levels of corn earworms can also be found in light traps. You can call the Crop Pest Hotline for the most recent trap catches (in state: 800-345-7544; out of state: 302-831-8851) or check our website at