Cabbage root maggot fly. This pest is a concern in spring or fall crucifer crops. Pupae overwinter in the soil wherever they fed on fall brassicas. First generation adults fly from April to May and lay eggs at the base of the crop stems. Maggots feed on roots and kill early cole crop seedlings. Immediately after planting, place spunbonded row covers in the field and seal the edges to keep cabbage maggots out. It is important to rotate crops as pupae can overwinter in the soil and flies may emerge under the row covers and damage the crop.
Flea beetles. There are many different species of flea beetles, each with a specific host crop. Because they typically spend the winter as adults around field edges, they can be effectively excluded by row covers if covers are in place soon after planting. Crucifer and striped flea beetles are tiny, black or striped beetles which cause shot-hole feeding patterns on any of the cabbage family crops. Covers can be used with spring or fall transplants, or all summer on direct-seeded crops, but are too hot for transplants in midsummer. Potato flea beetle causes similar damage to eggplant, tomato, and potato. Corn flea beetles cause feeding damage but are primarily a concern because they vector Steward's wilt. Excluding beetles with row covers prevents infection of young corn plants.
Spinach leafminer and Beet leafminer. These are pests of spring spinach, beets, and chard. The adult black fly emerges from overwintering sites in the soil and lays small eggs in the underside of leaves. Maggots tunnel inside the leaf, making unsightly pathways that render greens unmarketable. Row covers prevent flies from laying eggs on the leaves.
Striped cucumber beetle. This is a pest of cucumber, melons, summer squash, winter squash, and pumpkins. Row covers prevent feeding damage and transmission of bacterial wilt vectored by the beetle. Remove when flowers appear to allow for pollination by bees.
European corn borer. Adults emerge in late May or early June and lay eggs on corn. If row cover is left on into mid- to late June, after flight is peaked, it provides excellent protection to corn. If removed just as flight starts (e.g., first week in June) the larger, healthy corn that was covered may be just as infested as corn that was never covered. Row covers can be left on until tassel if enough slack is left for 3 to 4 feet of stalk growth.
Colorado potato beetle. This insect moves into potatoes and eggplant in late May and early June. Row covers should be removed before tuber initiation, which usually coincides with flowering, to prevent excessive heat.
Potato leafhoppers (PLH). Adults migrate from southern states where they overwinter. Adults usually arrive, reproduce and damage beans, potatoes and sometimes eggplants in June and July, but may last until September. Feeding causes a symptom known as hopper burn, where tips and edges of leaves begin to yellow, curl and die back. Adults and nymphs hide on the underside of leaves. Row covers can be used on beans from emergence until bud stage or the start of bloom. If removed for bloom, damage can be avoided and yields maintained. Lightweight row covers can also be used on potatoes to exclude PLH, flea beetles and Colorado potato beetles.