The<i>Rubus</i>Leafhopper and its Egg Parasitoid: An Endemic Biotic System Useful in Grape-Pest Management

The leafhopper Dikrella cruentata (Gillette) breeds throughout the year in the leaves of wild Rubus spp. in California, where its eggs are continually under attack by the parasitoid Anagrus epos Girault. In summer the Anagrus population has a seasonal numerical response to eggs of its alternative host, the grape leafhopper, Erythroneura elegantula Osborn, in Vitis spp. This response occurs regularly in the endemic eco-system where these 3 arthropods, together with native Vitis and Rubus, are commonly associated elements of the natural riparian biota. There is a valuable seasonal bridge of Anagrus to nearby commercial vineyards, but these parasitoids face formidable ecological barriers, including time and space, in reaching their grape leafhopper hosts in distant. unfavorably situated vineyards. The relationship of this host/parasitoid system to the pest management program on grapes is described.