Mexican Bean Beetle

Skeletonized foliage and spiny yellow blobs on leaves are two signs that Mexican bean beetles have found your bean patch. These beetles and their larvae feed on all members of the bean family, including cowpeas and soybeans. Severe feeding can kill the plants.

Mexican bean beetles resemble their ladybug cousins, but on close inspection their coloration is bronze rather than red, and they have sixteen black spots on their back. The larvae are fat, yellow, hump-backed, spiny, and about 1/3″ long. Adult beetles overwinter on plant debris. They emerge in late spring to feed for a few weeks and then lay clusters of yellow eggs on the undersides of leaves. Though Mexican bean beetles are fairly common in the U.S. east of the Mississippi River and in the Southwest and Mexico; they are more damaging in southern states.

• In areas where these beetles are a severe problem, grow early-maturing bean varieties, such as Provider, that produce a crop before bean beetles hit their stride.
• Plant a trap crop of soybeans and destroy the beetles on the soybean plants before they move elsewhere.
• Use garden fabric to protect young bean plants from adult beetles that are looking for a place to lay their eggs.
• Check leaf undersides for masses of yellowish eggs and squish any that you spot. Handpick adult beetles and larvae and dump them in soapy water.
• Encourage native predators and parasites of the beetles and their larvae.
• Clean up plant debris in the garden at the end of the season to reduce the number of overwintering adults.