Many species of flea beetles are found throughout the United States. Some species of flea beetles, like the corn flea beetle, will attack many different crops, but most species prefer a small group of related plants. Flea beetles is the general name applied to the beetles of the leaf beetle family (Chrysomelidae) that feed on the surface of leaves, stems and petals giving the appearance of small shotgun holes all over plants. They are small jumping insects (similar in appearance to fleas) commonly found in home gardens early in the growing season. A voracious pest, they will damage plants by chewing numerous small holes in the leaves, which make them look as if they have been peppered by fine buckshot. Some of the most problematic flea beetles are two that attack or brassicas, or crucifers: the crucifer flea beetle, which is all black, and the striped flea beetle, which is black with two light tan stripes on its back. When populations are high, flea beetles can quickly defoliate and kill entire plants. They feed most on hot sunny days and attack a wide variety of plants including beans, cabbage, corn, eggplant, potatoes, peppers, tomatoes, lettuce and most seedlings. On vegetable farms in the Northeast, one can find the horseradish flea beetle, potato flea beetle, and spinach flea beetle, to name a few.
Adults are small (1/10 inch long), shiny, dark brown or black beetles with large hind legs that allow them to jump when disturbed. Some species may have white or yellow stripes on their wing cases Adults are quite small, sizes ranging from 1/16 to 1/8 inch long with enlarged hind legs that help them leap away. They live underground and feed on the roots and tubers of young plants as well as on germinating seeds. Flea beetle control is an ongoing battle that relies upon three levels of approach. Control of flea beetles naturally starts with consistent cultural practices, physical barriers and even biological methods.
Flea beetles overwinter as adults under soil and leaf litter in brushy or woody areas surrounding fields, rather than in grassy areas right next to fields. Adults overwinter in the soil or garden debris and become active in the spring, feeding on host plants as new growth appears. They emerge in early spring when temperatures reach about 50 degrees, feeding on weeds or crops, if available. Females soon lay their eggs in the soil at the base of these plants. Tiny white eggs are laid on or in soil cracks around the base of plants. These hatch in about one week, and the slender white larvae feed on plant roots for approximately 2-3 weeks. Then they pupate in the soil for 11 to 13 days before emerging as adults. Delaying the planting dates of susceptible crops until after the overwintering beetles have emerged is one way to reduce damage to young plants. There are one to four generations per year, depending on species and climate.
Organic Control and Preventative Measures:
1. Plant or transplant susceptible crops into the garden as late as possible to avoid attacks from the early emerging flea beetles. Set out large healthy transplants rather than sowing seeds directly in the garden.
2. Trap crop method: This method involves growing plants that are more favorable to flea beetles than the crop you are trying to protect. Plant these trap crops all around the corners of your garden, several feet away from your precious vegetables. Giant mustard plants and radishes are good trap crops. Pull up and destroy or spray the plant with insecticide to ensure they don’t move further into the garden.
3. Remove and dispose of all weeds and crop debris from the growing area to ensure elimination of flea beetle habitats in your garden. Digging up the soil is also a good practice to kill over-wintering adults.
4. Since handpicking is not an option, household and handheld vacuums to suck away flea beetles can be effective in reducing pest numbers.
5. Mulching the ground around your plants can make it difficult for female beetles to lay eggs on the base of plants.
6. Attract or obtain beneficial insects such as baraconid wasps, soil-dwelling nematodes and the tachinid fly. Daisies, cosmos, yarrow, alyssum, dill, fennel, angelica, clover and cone-flower all help attract beneficial insects.
7. Plant vulnerable plants that are tolerable to shade in shaded areas. Flea beetles prefer the sun.
8. Plant resistant varieties that include ones with hairy or waxy leaves.
9. Inter-planting cabbages or broccoli with radishes can help save them as flea beetles prefer radishes.
10. Cover seedlings with fine insect proof netting to avoid damage from adult beetles.
11. Food grade diatomaceous earth spread on affected plants is excellent for reducing feeding on plants by adult flea beetles. It can also be used as a preventative measure.
12. Neem oil has been found to be useful against flea beetle populations.
13. Try a homemade spray such as the following: 2 parts rubbing alcohol, 5 parts water and 1 tablespoon organic liquid soap on susceptible plants. Garlic and pepper sprays and catnip tea sprays have been found to be effective too.
14. Sticky yellow traps will catch flea beetles but will deceive some beneficial insects too.