Bean Leaf Beetle

How to identify it

• Adults are about 1/4 inch, oval, usually yellowish green but sometimes red or orange, often with four black spots.^[1]
• All have a black triangle at the top of the wing covers and black margins along the edges.^[1]

Look-alikes

Where it lives

Minnesota Extension notes it's more common in southern than northern Minnesota; it feeds on snap beans, soybeans, clover, dry beans and related plants.^[1]

US map: public records from 35 states since 1990 (GBIF). View the map

Biology and life cycle

Adults overwinter in leaf litter and grass clumps and emerge from mid-May to early June.^[1]

Females lay clusters of about 12 orange eggs in soil at the base of beans; larvae feed on roots, causing minor damage.^[1]

There's usually one generation a year in Minnesota, two in the south of the state.^[1]

Damage and signs

• Adults chew round 1/8-inch holes under leaves and can defoliate seedlings; pod feeding is cosmetic.^[1]

Health risk

It feeds on plants; Minnesota Extension mentions no risk to people.^[1]

Control

Prevention

Delay planting snap beans to early or mid-June in southern Minnesota to avoid spring beetles.^[1]

Keep them out

Floating row covers with secured edges keep beetles off.^[1]

Sanitation

Clean up leaf litter around the garden to remove overwintering sites.^[1]

Traps and physical control

Hold a pail under plants and tap them; beetles drop when disturbed.^[1]

Common questions

What's chewing round holes in my green bean leaves?

Bean leaf beetles make round 1/8-inch holes on the undersides of leaves.^[1]

When should I check?

Check early in the season, in the afternoon between noon and 4 p.m.^[1]

Sources

1. University of Minnesota Extension, “Bean leaf beetles (Yard and garden insects).” extension.umn.edu/garden-and-home/yard-and-garden/yard-and-garden-insects/bean-leaf-beetles (accessed 2026-10-06)
2. iNaturalist, “Cerotoma trifurcata taxon page (order and family).” www.inaturalist.org/taxa/216533 (accessed 2026-10-06)