Here are tips on how to identify and get rid of Mexican bean beetles.
What are Mexican Bean Beetles?
Found throughout the United States, these pests do the same type of damage as Japanese Beetles, leaving skeletons of foliage up and down your garden. Mexican Bean Beetles are a relative of the ladybug, and they look the part. They are small, about ¼ inch long, and have sixteen black spots displayed on their tan yellow bodies. Don’t be fooled by the name, although they are partial to beans, they can also affect your pea, beet, squash and tomato crop.
How to Identify Mexican Bean Beetles
The larvae of the Mexican Bean Beetle start out as yellow eggs on the undersides of plant leaves, which are laid sometime in late spring to early summer. Adult beetles overwinter by burrowing in the soil or left over plant debris. They usually begin to emerge in early spring when the soil warms, but can also stay hidden and emerge at any time during the summer.
- Females will feed for 2–3 weeks before laying eggs.
- Females are capable of laying eggs as frequently as every 2 days, and be laid in clusters of 30–40.
- Eggs will hatch 1–3 weeks later, and larvae will feed on foliage before the pupal stage. Larvae are yellow, robust, and spiny, and grow to about ½ inch.
- Cocooning larvae will rest on the undersides of leaves for 5 days before emerging as an adult beetle.
Usually damage is to the leaves only, but in some cases, Mexican Bean Beetle damage can result in lower crop yield, or even the demise of plants.
How to get rid of Mexican Bean Beetles
- Bush beans are less susceptible than pole beans, and also require less maintenance.
- Handpick larvae and beetles, and destroy them.
- Check undersides of leaves, especially from early spring until June, to look for and remove eggs and pupal stage larvae.
- Rosemary is said to help deter Mexican Bean Beetles. Consider planting some of this herb around susceptible plants.
- Clean up your garden at the end of the season, and till soil in the spring before planting. This will unearth any overwintering adult beetles.
- Check with your local Cooperative Extension  for a list of approved pesticides and insecticides if the problem gets out of hand.