leafhoppers, members of the insect family Cicadellidae which can cause both direct and sometimes serious indirect damage to vineyards. In California, both the grape leafhopper, Erythroneura elegantula, and the closely related and biologically similar variegated grape leafhopper, Erythroneura variabilis, cause damage to grapes. They begin to feed on grapevine foliage as soon as it appears in spring, and do so by sucking out the contents of leaf cells. As injury progresses, heavily damaged leaves lose their green colour and photosynthesis is much reduced. table grapes are spoilt by spots of leafhopper excrement. The damage caused is in direct proportion to the numbers. When there are 20 or fewer leafhopper nymphs per leaf, no control is required.