Leafhoppers feed on many different fruit, vegetable, flower, and woody ornamental hosts. Most species of leafhoppers feed on only one or several closely related plant species. Adults mostly are slender, wedge-shaped, and less than or about equal to 1/4-inch long. Leafhoppers generally are varying shades of green, yellow, or brown, and often mottled. Some species are brightly colored, while others blend with their host plant. Leafhoppers are active insects; they crawl rapidly sideways or readily jump when disturbed. Adults and nymphs and their pale cast skins are usually found on the underside of leaves.
Leafhoppers may sometimes be confused with aphids or lygus bugs. Look for leafhoppers or their cast skins on the undersides of affected leaves. Look at their actions; they are faster than aphids and run sideways and jump. Lygus bug nymphs are light green and also move much faster than aphids. They can be identified by their red-tipped antennae. Aphids can be distinguished by two tubelike structures, called cornicles, protruding from the hind end. One or more long rows of spines on the hind legs of leafhoppers and characters on their head distinguish leafhoppers from most other insects they resemble.
Some common leafhopper species in gardens and landscapes are the rose leafhopper, grape leafhopper, variegated leafhopper, potato leafhopper, and the aster leafhopper.
Leafhoppers go through incomplete metamorphosis in their development. Female leafhoppers insert tiny eggs in tender plant tissue, causing pimplelike injuries. Overwintered eggs begin to hatch in mid-April. Wingless nymphs emerge and molt four or five times before maturing in about 2 to 7 weeks. Nymphs resemble adults except that they lack wings; later-stage nymphs have small wing pads. There is no pupal stage. Leafhoppers overwinter as eggs on twigs or as adults in protected places such as bark crevices. In cold-winter climates, leafhoppers may die during winter and in spring migrate back in from warmer regions. Most species have two or more generations each year.
Leafhopper feeding causes leaves to appear stippled, pale, or brown, and shoots may curl and die. Some species cause a diamond-shape yellowing from the leaf tip. A few species secrete honeydew on which foliage-blackening sooty mold grows. Black spots of excrement and cast skins may be present on leaves and/or fruit. Some leafhopper species transmit plant diseases, but this is troublesome mostly among herbaceous crop plants.
Because of their mobility, leafhoppers are difficult to control. Fortunately control is rarely needed. General predators may have some impact. In grapes, rely on specific natural enemies. Remove alternate hosts to reduce populations that could otherwise later migrate into the crop. Insecticidal soap or narrow-range oil can be applied to infested foliage to reduce high populations of leafhopper nymphs but will not reduce virus transmission significantly; thorough coverage of leaf undersides is important. It is very difficult to control adults effectively and no control is recommended.
Adult potato leafhopper
White speckled markings left by leafhoppers
Variegated leafhopper adult