Leafhoppers feed on many vegetables and small fruits. They generally feed on the undersides of leaves, sucking the sap, which causes stippling. Severely infested vegetable and small fruit plants may become weak and produce little edible fruit. One leafhopper, the aster leafhopper (Macrosteles fascifrons), transmits aster yellows, a plant disease that can be quite damaging. (For further details about aster yellows, see Aster Yellows.) Leafhoppers at all stages of maturity are active during the growing season. They hatch in the spring from eggs laid on perennial weeds and ornamental plants. Even areas where the winters are so cold that the eggs cannot survive are not free from infestation because leafhoppers migrate in the spring from warmer regions.
Spray infested plants with an insecticide containing pyrethrins, malathion, or carbaryl, or with an insecticidal soap. Be sure to cover the lower surfaces of the leaves. Repeat the spray as often as necessary to keep the insects under control. Allow at least 10 days between applications. Make sure that your plants are listed on the product label. Eradicate nearby weeds, especially thistles, plantains, and dandelions, that may harbor leafhopper eggs. (For more information about controlling disease-carrying insects, see Vectors of Plant Diseases.)
