Bean leaf beetle

About

A small beetle about a quarter inch long, yellow, orange or red, usually with black spots and always with a black triangle at the base of the wing covers. It is best known as a soybean pest but also feeds on snap beans and southern peas in home gardens.

Spotting it

Damage

Adults chew small, round holes between the leaf veins and scar the pods, which lets in rot. Damage is worst on young seedlings, and the beetles can spread bean pod mottle virus.

How to find it early

Check seedlings and leaf undersides for small round holes and for the beetles themselves.

When

April through fall; worst on seedlings in spring.

Life cycle

Adults spend the winter in leaf litter, mostly in wooded areas, and become active in spring; larvae feed on roots and root nodules. There are about three generations a year in the South, two in the central states and one in Minnesota.

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Floating row cover Barrier

   Cover young bean plants with row cover, since seedlings suffer the most damage (Mississippi State).

2. Home-garden insecticides Conventional spray

   Mississippi State lists bifenthrin, permethrin, zeta-cypermethrin and malathion for bean leaf beetle in home gardens.

   All of these are highly toxic to bees and kill natural enemies. Keep sprays off open flowers, and follow the label and pre-harvest interval.

Plants it goes after

Dry beans (pinto, black, kidney, navy), Edamame, Green beans (snap beans), Southern peas

Pressure by region

It is a pest in most soybean-growing parts of the U.S., with three generations in the South and one in Minnesota. No source rated it by region, so the moderate ratings are estimates, and the West, Alaska and Hawaii are rated low as estimates.

Ratings come from extension sources where available; some are estimates, as noted above.