The dynamics of grape leafhopperEmpoasca vitisGöthe populations in southern Switzerland and the implications for habitat management

Abstract

The life cycle of Empoasca vitis and its most important parasitoidAnagrus atomus in southern Switzerland can be divided into three phases. In phase I the adults of E. vitis move from overwintering sites, i.e. primarily conifers, over deciduous plants into the vineyards. The parasitoid A. atomus on the other hand, appears to overwinter in leafhopper eggs, mainly on roses and blackberries. It subsequently completes one generation in leafhopper eggs primarily on blackberries and hazelnuts, before it attacks E. vitis eggs in the vineyards. For phase II, a population model with time-varying age structures and stochastic properties was constructed for E. vitis. For this purpose a time-varying distributed delay model with attrition was constructed. Given the calibrated initial density of overwintering females, the model predicts an unacceptable number of E. vitis for the growing season. However, if egg parasitism of A. atomus and Stethynium triclavatum is introduced into the model as an external variable, E. vitis densities are predicted which are economically irrelevant. Inphase III E. vitis adults leave the vineyards for the overwintering sites. The model shows the importance of the parasitoid A. atomus during phase II. A. atomus should be favoured by surrounding the vineyards with host plants carrying leafhoppers' eggs. Consequently, habitat management measures for E. vitis control could be applied to the surroundings of the vineyards.

Spatial and temporal distribution of Empoasca vitis within a vineyard

“…Before spring immigration into (and after autumn emigration out of) vine plots, adults can be observed on a wide range of deciduous plants present in the vineyard vicinity: the intermediate host plants ( Cerutti et al , 1991;van Helden et al , 2003 ). Two to four sexual generations develop in vineyards ( Cerutti et al , 1991;Bosco et al , 1996;Genini, 2000;Boell & Hermann, 2004 ), and recurrent inter-plot summer migrations are assumed (Decante & van Helden, 2003, 2006.…”

“…Before spring immigration into (and after autumn emigration out of) vine plots, adults can be observed on a wide range of deciduous plants present in the vineyard vicinity: the intermediate host plants ( Cerutti et al , 1991;van Helden et al , 2003 ). Two to four sexual generations develop in vineyards ( Cerutti et al , 1991;Bosco et al , 1996;Genini, 2000;Boell & Hermann, 2004 ), and recurrent inter-plot summer migrations are assumed (Decante & van Helden, 2003, 2006. Adults and nymphs feed on phloem sap, and punctures provoke leaf necrosis (hopperburn: Backus et al , 2005 ) that result in delayed maturity and reduced sugar content ( Vidano et al , 1987;Candolfi et al , 1993;Delbac et al , 1996 ).…”

“…Most of the studies on E. vitis plot populations focus on the influence of the surrounding vegetation (hedges, woodlands and grasslands) as a source of natural enemies, mainly egg parasitoids ( Cerutti et al , 1991;Baur et al , 1998;Genini, 2000;van Helden et al , 2003;Boell & Hermann, 2004 ), but also as alternative host plants for the polyphagous E. vitis ( Cerutti et al , 1991;Bosco et al , 1996 ). Finally, the surrounding vegetation may also generate edge effects through microclimatic modifications, shading effects, competition for water and nutrients, air flows, etc.…”

Influence of grapevine cultivars on the leafhopper Empoasca vitis and its egg parasitoids

“…The role of oophagous mymarid parasitoids, in particular Anagrus atomus (Linnaeus) (Hymenoptera: Mymaridae), and other biological control agents has been described (Arzone et al 1988;Vidano et al 1988;Cerutti et al 1991;Picotti and Pavan 1993;Viggiani 2003). The host plant can influence not only the ovipositional activity of E. vitis, but also that of A. atomus .…”

Larval development of Empoasca vitis and Edwardsiana rosae (Homoptera: Cicadellidae) at different temperatures on grapevine leaves

“…While E. vitis is long known as a widespread insect in Southern European vineyards (Cerutti et al. 1991), it has only just recently been recognized as an important pest in cooler climates such as Middle European winegrowing regions (Böll and Herrmann 2004).…”