Mexican Bean Beetle

Okay, Mexico, we love your tacos and tomatillos, but please take your beetles back! They're eating all our beans. They remind me of those slimy Colorado potato beetles except that these (larvae) are yellow and hairy. If you haven't seen one in your garden, they look like this:

(picture via http://www.uri.edu/ce/factsheets/sheets/mexbeanbeetle.html)

The adult Mexican beetle looks like a yellow or copper colored ladybug but don't be fooled. They are evil.

Pick the beans that are ready, flick those beetles off and step on them.

According to Frank A. Hale, Associate Professor of Entomology and Plant Pathology at the University of Tennessee, "The adult Mexican bean beetle overwinters under leaves or other debris in grassy, weedy areas and around fence rows or trees. The adults move into the bean fields and gardens soon after the bean plants emerge. The adults feed for a week or two before laying their yellow egg masses on the underside of the leaves. The eggs hatch in five to 14 days."

"The bright yellow larvae are oval-shaped with six rows of branched spines. The larvae feed for two to five weeks. Larvae and adults feed on all types of beans and are an occasional pest of soybeans. They generally feed on the underside of leaves, removing all of the leaf tissue except the clear layer on the upper side of the leaf, called the epidermis."

"This damage, called "window-paning," gives the leaves a lace-like or skeletonized appearance. The remaining leaf tissue turns brown in a couple of days, giving the field a burnt cast. New pods and stems are often attacked, and severely damaged plants may die prematurely."

You can use a pyrethrum (chrysanthemum) based pesticide but there have been some studies that question the safety of these products. A cedar oil product might be better and is comparable in cost. Vacuuming is another way to get rid of these pests. If you want a physical barrier, try floating row covers from Johnny's Seeds.

August 28, 2008

Mexican Bean Beetle