Mexican Bean Beetle

The Mexican bean beetle is an injurious pest of beans. Both adults and larvae feed on leaves of several plants, including garden beans, cowpeas and soybeans, leaving the leaves skeletonized with a lace-like appearance. Although feeding occurs mainly on the leaves, young pods and even the stems may be attacked and destroyed. Severely affected leaves often dry up and drop off the plant; serious infestations usually result in the death of young plants.

Description

The Mexican bean beetle is one of the few harmful members of the lady beetle family; yellow to coppery-brown adults resemble large lady beetles. They are about 1/4 inch long with eight small black spots on each wing cover. Full grown larvae are yellowand have six rows of black-tipped spines on their backs.

Life Cycle

Adult beetles overwinter in hedge rows, ditch banks, and woodlands and may attack plants soon after seedlings emerge. The adults feed for approximately two weeks before depositing orange-yellow egg masses on the underside of leaves. Eggs hatch in 5-14 days and larvae feed for two to five weeks before pupation. The greatest amount of injury occurs in July and August, and the adults begin to disappear in late summer.

Control

• Plant early and fast-maturing varieties.

• Plant bush beans instead of pole beans and pick pods as soon as they mature.

• "Floating-row" covers work well as protective barriers.

• Use carbaryl (Sevin) in home gardens, following instructions on productlabel.

Richard A. Casagrande and David B. Wallace, 1999