Mexican Bean Beetles: Identification, Control & Prevention

Mexican bean beetles (ladybug relatives) resemble yellow/orange ladybugs but skeletonize foliage like Japanese beetles. Found throughout US except driest areas. Attack beans, peas, beets, squash, tomatoes.

Lifecycle

Eggs: yellow, clusters of 30–40 on leaf undersides (late spring/early summer). Larvae: yellow, spiny, black-tipped spines, ~1/2". Adults: 1/4", 16 black spots on tan-yellow, aging to orange-yellow. Overwinter in soil/debris; emerge spring. Multiple generations.

Damage

Skeletonize leaves from underside. Mostly leaf damage; occasionally lower yields or kill plants. Larvae may feed young pods.

Control

• Handpick larvae, beetles, eggs, pupae (check undersides spring–June).
• Consult extension for approved pesticides if severe.

Prevention

• Bush beans less susceptible than pole; early crops less hit than late (peak midsummer).
• Rosemary deters; marigold may help.
• Fall cleanup; spring tilling exposes overwintering adults.
• Attract beneficial insects.
• Old remedy: summer savory and nasturtium repel.

Plants Affected

• Beans