Bean leaf beetle identification & organic control
Cerotoma trifurcata
How to identify bean leaf beetle
A small, variably colored beetle (red, yellow, or tan, usually with black spots and a black triangle behind the head) that chews round holes in bean leaves and can scar pods.
Crops attacked by bean leaf beetle
Bush bean, Pea.
Adults chew round holes between leaf veins ('shot-hole' feeding) and can scar pods; larvae feed on roots and nodules underground, with lesser impact.
Life cycle
- Overwintering adult (Winter (in debris)) — None.
- Adults emerge (Spring) — Feed on emerging bean seedlings.
- Larva (root feeding) (Summer) — Minor root and nodule feeding.
- New generation adults (Mid-late summer) — Second generation feeds on leaves and pods.
Natural, organic bean leaf beetle control
- 1. Row cover young seedlings · medium effort
Protects the most vulnerable stage from early adult feeding.
When: At emergence
- 2. Handpick adults · low effort
Beetles drop and play dead when disturbed; hold a cup underneath and tap the plant.
When: Weekly
Fastest-fix products
- Row cover — Protects seedlings during the most damage-sensitive window. · Garden centers, Amazon
Prevention
- Rotate beans to a new bed yearly.
- Till bean debris after harvest to expose overwintering beetles.