Mexican Bean Beetles – Prevention

Q: For the first time in twenty years of gardening I’ve been invaded by Mexican bean beetles. They stripped my bean plants, then the squash plants, then cucumbers, and then the sunflowers. How can I prevent them next year?

A: There is no way to prevent them. But you can forestall a big population buildup by keeping a sharp eye out for their eggs when your beans are young. The eggs are orange-yellow, similar in size to a grain of rice, and found in clusters on the undersides of bean leaves. At this point, you can mash them with your gloved fingers. If unmolested, the eggs hatch into bright yellow, bristly things that are beetle larvae. Both larvae and adults feed on squash, bean, and pea leaves, leaving large, tattered holes in the leaves. Adults closely resemble a lady beetle. They have eight black spots on each wing. You might also spot squash beetles and larvae. They have seven wing spots. The control of both insect adults is the same: garden insecticide.