Role of winter host plants in the phenology and vineyard colonization pattern of Zygina rhamni (Hemiptera: Cicadellidae: Typhlocybinae)

ABSTRACT Zygina rhamni Ferrari (Hemiptera: Cicadellidae: Typhlocybinae) is a mesophyll-feeding leafhopper that infests grapevine, Vitis vinifera L. This leafhopperÕs overwintering strategy and the dynamics of its vineyard colonization, relative to the distance between the grapevines and the winter host plants and different grapevine vegetative densities, are described herein. This species shows a facultative heteroecious life cycle. In autumn, it migrates from vineyards to bramble, Rubus gr. fruticosus, and rose, Rosa chinensis Jacquin. On these host plants, females lay eggs that start to hatch at the end of March. Adults that developed on bramble colonize grapevines beginning in May; the leaf fall of rose, which takes place during the Þrst half of April, probably causes the death of unhatched eggs and nymphs.Wefound that overwintering females can move back to vineyards and lay eggs until early June. The dynamics of vineyard colonization by the leafhopper involved initial concentration in areas close to bramble (MayÐearly July) with subsequent, progressive spread through the vineyards, with concentration in areas of high vegetative density. Leafhopper presence was negligible in areas of vineyards with levels of vegetative density below a certain threshold.