Mexican Bean Beetle a pesty cousin to the ladybug

Mexican Bean Beetle (Epilachna varivestris) is one of two harmful cousins of the ladybugs.mexican-bean-beetle
A young adult Mexican bean beetles are round, about 1/4 inch long, and yellow, but as they age their color becomes coppery. Though the Mexican bean beetle has mandibles that are typical of chewing insects, it does not swallow bits of food. Rather, it chews its food and consumes the plant juices. The leaves of garden beans such as snap, kidney, pinto, and lima, soybeans, alfalfa, clover, peanut, okra, eggplant, squash, and various weeds are its favorites.

In the winter adults live along fences, woodlots, or in stubble and can usually be found within 1/4 mile of the host plants and hibernate. In the spring as the weather warms, the beetles fly to the bean, sorgum plants, feed for a week or two, and then mate.

The female after mating will lay 400 to 500 eggs on average, but sometimes as many as three times this number have been recorded. The eggs, yellow and oval shaped, are laid in clusters on the undersides of leaves over a period of 3 to 6 weeks.

Larvae of the Mexican bean beetle hatch in 5 to 14 days and are about 1/3 of an inch long have sixteen black spots, eight on each wing cover with six branching spines on each segment of the bright yellow and feed for 2 to 5 weeks on leaves; in their early growth stages, they feed exclusively on the lower surface of the leaf. Bean pods may also be scarred, but this damage is seldom considered economic. Then they pupate on the undersurfaces of leaves. The pupae are bright yellow and have only remnants of larval spines. Adults emerge 7 to 10 days later and live from 4 to 6 weeks.In certain areas of the country the weather may allow for three generations of these beetles to emerge.

Both larvae and adults impart a skeletonized or lacy appearance to leaves by consuming the leaves’ epidermal layers. Heavily infested soybean fields take on a dusty appearance as leaves shrivel and turn brown.

Excerpts courtesy of Clemson University – USDA Cooperative Extension

Image courtesy of UIWeb


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