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Variegated leafhoppers (Erasmoneura variabilis) are reddish brown mottled leafhoppers (family Cicadellidae) about 3 mm (0.1 in) long, first described and reported in Arizona and southern California in the 1920s. Variegated leafhoppers live mainly on Vinis (grapevine) species, puncturing cells from the underside of the leaf and sucking out the sap. In the 1980s E. variabilis became established in the San Joaquin Valley and since then have surpassed numbers of the closely related E. elegantula (the western grape leafhopper) to become the most serious pest of cultivated grape vineyards in California. The explosion of the California E. variabilis population is thought to have occurred partly because Anagrus wasps, which so effectively parasitize the eggs of the western grape leafhopper, are far less effective for E. variabilis since this hopper deposits their eggs more deeply into the leaf (Dmitriev 2013; Daane and Costello 2000).
In light infestations variegated leafhoppers cause leaf spotting, in years with heavier infestations their feeding causes defoliation and stress the vines, making the plants susceptible to other pests and reducing the sugar content and quality of the fruit. Furthermore, the hoppers’ sticky sweet droppings cause unsightly fruit spotting and cause damaging growth of sooty mold (Daane and Costello 2000). In California E. variabilis and E. elegantula are two of the most targeted species for chemical pesticides. Although pesticide applications produce the best control of E. variabilis, application of chemicals significantly effect natural predators of these pests (Hanna et al. 2003) and other methods of eradication actively being explored, including alternative irrigation strategies to water-stress and reduce the vigor of the vines, subsequently inhibiting these pests (Costello 2008; Daane et al. 1995), and pruning basal leaves early in the season (UC IMP online 2009). Release of predatory green lacewings (Chrysopa spp.) show some promise for population control, but current release methods led to increased predator mortality and variable outcome in reducing hopper numbers; more research is investigating better ways to introduce lacewings to the vineyards (Daane 1996; Daane and Costello 2000).