The best way to control leafhoppers is to encourage populations of leafhoppers' natural predators. These include parasitic wasps, predatory mites, lady beetles, lacewings, minute pirate bugs and spiders. Some predators can be purchased from garden supply centers. Removing the insects' favorite hiding places is also helpful.
Leafhoppers are small wedge-shaped insects that feed on plant juices in both their immature and adult forms. They attack a wide variety of fruit and vegetable plants. Their feeding removes the contents of plant cells and leaves pale yellow spots as evidence of their presence. Plants may also show severe leaf distortions in response to the leafhoppers' toxic saliva. Leafhoppers cause stress to the plants, which can lower crop yields and can also spread plant diseases.
Leafhoppers usually wait out the winter in garden trash and debris. In vineyards, removing the plants' basal leaves and lateral shoots at the time the grapes set and during the two weeks that follow can reduce leafhopper populations by up to 50 percent. Strong sprays of water can wash leafhopper nymphs from trees. Young nymphs are also vulnerable to insecticidal soaps, narrow-range oils and kaolin clay but become less vulnerable as they approach maturity. Heavy infestations may require spot treatment with botanical insecticides.