Pest Profile: Flea Beetles
In the early summer vegetable patch, the damage caused by insect pests is often apparent before the pest itself. Flea beetles, residing on the undersides of leaves in cool weedy areas, are one such pest. These black or brown insects are small, only 1/10 inch long. Like their namesake, when disturbed, the flea beetle will use its enlarged hind legs to jump like a frog off the plant and usually out of sight. These insects feed primarily on vegetables like eggplants, potatoes, spinach, and members of the cabbage family. Adult beetles emerge from the soil during the spring to feed on foliage and lay eggs on the roots of the plants.
The larvae hatch in about a week and eat the roots of their host for 2 to 3 weeks. There can up be up to four generations per year. The damage manifests as small, round holes, leading to a shothole appearance. Although flea beetles usually have little effect on yields of established plants, infestations can kill seedlings and lead to significant aesthetic decline.
To prevent flea beetle infestations, start by cultivating the soil before and after planting to destroy any flea beetle eggs or larvae that may be burrowing in the soil. Once planted, cover the seedlings or vegetable shoots with a floating row cover and a thick layer of mulch. The row covers will deter adults, while the mulch will disrupt larval stages. Deploy a trap crop of radishes or daikon some distance from your main crop to divert the flea beetles should they come into your garden.
When your garden is overrun with flea beetles, Queen Anne’s lace, dill, parsley, thyme, and mint will help to not only attract the beetle’s predators such as brachonid wasps and tachinid flies, but also mask the chemical cues from host plants. And if you’re feeling extra tidy, flea beetles can even be vacuumed off your plants!