Bean Leaf Beetle (Cerotoma trifurcata) adults overwinter in protected areas and move into gardens and fields as temperatures warm. They feed on bean leaves, chewing numerous small, round holes between the veins. Later in the season they may also feed directly on pods, leaving scars that can reduce quality and provide openings for disease. The larvae live underground and feed on roots and root nodules, but adult feeding is usually the damage gardeners notice.

How to Fix It
Hand-pick: Knock beetles into soapy water, especially early in the morning when they are less active.
Protect young plants: Use insect netting or row cover while plants are small, removing it when flowering begins so pollinators have access.
Control weeds and volunteers: Remove nearby legumes and weedy hosts that can harbour beetles.
Clean up the garden: Remove bean debris after harvest and eliminate volunteer bean plants.
Plant later where practical: Delaying planting can help young beans avoid heavy feeding from overwintered adults.
Encourage beneficial insects: Predators and parasitoids help suppress beetle populations.
Spinosad: If damage is severe, spinosad can control feeding beetles; avoid spraying flowers or when bees are active.