Mexican Bean Beetles

Identification

Adult Mexican bean beetles are copper-colored, ladybug-like beetles with 16 black spots (see lower right image in this post’s featured photo). Their larvae are light yellow with soft, bristly spines.

Damage

Adults and larvae consume leaf tissue down to the veins. Occasionally, they also feed on flowers and bean. The larvae are often found on leaf undersides.

Prevention

Plant lots of flowering herbs as they attract a beneficial, predatory wasp that feeds on the beetle larvae.

Physical control

Cover bean plants with floating row cover from the time of germination until flowering.

Chemical control

It is highly recommended to try physical prevention/control methods before resorting to chemical control. Hot pepper wax and spinosad are both useful for the control of Mexican bean beetles. Check local regulations (or your local Extension Office where applicable) to identify which products can be used in home gardens in your area. Follow label instructions carefully for safe and effective insecticide application and to ensure that edible crops are safe to harvest. Test insecticide on a few plants before widespread application. Look for the most selective insecticide to minimize harm to beneficial insects- even some “selective” and "natural" insecticides can still negatively impact beneficial insects. Where possible, apply contact-based insecticides in the late evening and try to avoid spraying during blooming to minimize negative impacts on pollinators- in some cases the insecticide may need to be hosed off in the morning to avoid contact with pollinators. Do not spray spinosad on flowering plants.