Blister Beetles
Epicautaspp., Meloidae, COLEOPTERA


DESCRIPTION (several species)

Adult - Blister beetles are slender insects 12 to 19 mm long. They have prominent heads and may be black with yellow margins or black and yellow striped.

Egg - The yellow cylindrical eggs are 1.3 to 1.8 mm long.

Larva - Each of the seven larval instars differ in size, shape and color. They can be 2.5 to 13 mm long, slender to plump, and white to yellow or brown. All instars have three pairs of short ventral legs and 12 body segments, excluding the head.

Pupa - The white, 10-mm-long pupae darken gradually beginning with the eyes.


BIOLOGY

Distribution - Blister beetles are found throughout the continental U.S. and agricultural areas of Canada. Although fairly common in North Carolina, they are infrequently pests of importance.

Host Plants - Blister beetles have a wide host range. Important vegetable hosts include potato, tomato, melon, eggplant, sweet potato, bean, pea, cowpea, pumpkin, onion, spinach, beet, carrot, pepper, radish, corn, and cabbage.

Damage - Some species of blister beetles feed on flowers but most species are strictly foliage feeders. This latter group feeds gregariously, occasionally damaging foliage and stunting plant growth. Black stringy excrement often is found on heavily infested plants. Blister beetles also have been known to transmit the disease organism which causes southern bacterial wilt of potatoes. Larvae, on the other hand, are considered beneficial insects because they feed on grasshopper eggs.

Life History - Blister beetles have an unusual life cycle. They usually overwinter as sixth instar larvae 2.5 to 4 cm deep in the soil. In spring, resting larvae molt into active nonfeeding larvae which soon pupate. Adult blister beetles begin to emerge in June. Adults can be found well into September but are most abundant in July. During summer months, they congregate and feed voraciously on foliage or flowers (depending upon the particular species of beetle). Two to 3 weeks after mating, each female deposits up to six egg masses in the soil. These masses may contain 50 to 300 eggs apiece. Active larvae hatch from the eggs 1-1/2 to 3 weeks later and search for grasshopper egg cases. A few days after locating and feeding on the eggs, the active larvae molt and become fairly inactive. The grubs continue to feed on the eggs and molt until they are fat, almost legless fifth instars. These larvae create oval hibernating chambers in the soil, molt into sixth instars, and overwinter. Development usually continues the following spring but the larvae may remain inactive for as long as two years. Sometimes fifth instars molt directly into the pupal stage, by-passing the last two larval instars. As a general rule, however, blister beetles complete one generation each year.


CONTROL

Blister beetles often appear suddenly and may cause much damage before they are detected. Therefore, insecticides are generally applied as an emergency measure after beetles are found on a crop. Control failures usually are attributed to applying insecticides too sparingly, too late. Spot treatment is usually adequate. For recommended insecticides and rates, consult the current North Carolina Agricultural Chemicals Manual

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