By Sandy Feather ©2015
Penn State Extension
Q. I planted my first vegetable garden this year, and things are growing surprisingly well. The only real problem is my eggplant. The leaves are full of tiny holes and look more like lace than leaves. I do see some small black bugs, but they jump away when I try to look at them more closely. Can you tell me what they are and how to get rid of them?
A. The eggplant flea beetle (Epitrix fuscula) is one of this plant’s most common pests. Other species of flea beetles also feed on cole crops (cabbage, broccoli, cauliflower, etc.), potatoes and sweet corn. High populations of these pests can slow development of transplants and severely limit photosynthesis by destroying the foliage, which in turn reduces the yield from infested plants.
Flea beetles are small (1/16th to 1/8th of an inch), black or brown beetles with hard shells. They jump like fleas when disturbed. Adults overwinter in the soil and on plant debris.
They emerge in spring and feed on weeds until vegetable garden crops are planted. After feeding briefly, they lay their eggs in the soil. Tiny gray grubs hatch in two or three weeks, and feed on plant roots and the surface of the leaves. Fortunately, larval feeding does not usually cause damage to plants. Then they pupate in the soil and hatch out as adults, which may feed for two months. The tiny holes in the leaves are characteristic of adult feeding.
Cultural controls include good weed control in and around the vegetable garden. This removes the alternate food source for the overwintering adults until garden transplants are planted out in the garden. Good garden sanitation -- the prompt removal of annual vegetable plants at the end of the growing season -- also helps eliminate overwintering sites.
Flea beetles are much more damaging to young transplants than more mature plants. If you can protect the young plants until they start producing fruits, you should get a good yield. If you practice crop rotation, you can exclude flea beetle adults from susceptible crops with floating row covers (Reemay, Garden Blanket). Plant the transplants and cover them with the floating row cover. Leave enough excess fabric to allow room for the plants to grow, then seal the edges with soil.
Once the plants are half-grown and start to bloom, you will have to remove the covers to allow bees and other pollinators to work the flowers. At that point, monitor the plants to see how large a population of flea beetles is active on them. If their population is not high, the plants can probably live with them. Otherwise, you can begin protecting them with insecticide applications.
Another option is to use a kaolin clay product such as Surround. This is a particle film that is sprayed on plants and protects them by creating a physical barrier to pest feeding and egg laying. Kaolin clay has a couple modes of action; it may make host plants unrecognizable to pests and it acts as an irritant to them. You can use it instead of row covers or begin using it once you remove the row covers. Kaolin clay is a thick material and works best with sprayers that have mechanical agitation to keep the clay particles in solution. You may find that it clogs conventional pump-up sprayers.
Insecticides labeled to control flea beetles include botanical insecticides containing pyrethrins (Pyganic), biological insecticides such as spinosad (Captain Jack’s Deadbug Brew), as well as conventional insecticides such as Sevin (carbaryl). Some formulations of neem (azadirachtin) may also be effective. Always read and follow label directions for mixing instructions and intervals between applications.