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V. vitifoliae damage can appear initially as a few dead or declining contiguous vines in a vineyard.
Small galls, about the size of half a pea, develop on the leaf surface, sometimes so numerous as to cover practically the entire leaf. The galls are open on the underside of the leaf. Although leaf galling by V. vitifoliae does not normally cause significant losses in grape production, severe infestations do cause considerable distortion and dropping of affected leaves late in the season.
Numerous knots or galls form on grapevine roots, with rotting of the roots, yellowing of the foliage and general decrease in vigour of the vines. Death of susceptible vines may result within 3-10 years.
Flooding of vineyards for several weeks can help in reducing pest populations (Torregrosa et al., 1997) and was classically used in the past.
Use of resistant rootstocks has been the main and most successful control measure for many decades. However, recent studies indicate that this practice might become less effective in future if new biotypes of V. vitifoliae develop (Williams and Shambaugh, 1988). In Italy, new biotypes have been reported to develop in several parts of the country, distinct from those which were originally introduced from the USA (Strapazzon and Girolami, 1985a). A combined German and New Zealand research project demonstrated differences in susceptibility of several rootstocks after inoculations with New Zealand and German populations of V. vitifoliae (King and Rilling, 1985), and in the USA research studies showed that certain populations of the pest overcame the resistance of even highly resistant cultivars (Granett et al., 1985). Naturalized rootstock species (e.g. V. riparia), escaped from cultivation, may support phylloxera populations of greater genetic diversity (Kocsis et al., 2002).
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
V. vitifoliae is the most destructive pest of grapevines known in Europe and the western USA and has become an important pest of wine grapes in Pennsylvania. Within 25 years of its introduction into France from America (in about 1860) it had destroyed nearly one-third of the vineyards in the country - more than 100,000,000 ha - with incalculable economic and social consequences. This was because the European grapevine cultivars then grown were highly susceptible. The solution found was to replant with European cultivars grafted onto American rootstocks, a practice which is now almost universal wherever V. vitifoliae occurs. The pest still represents a serious threat to the few regions where susceptible grape cultivars are still cultivated on their own roots (rather than on resistant rootstocks). It is also more damaging in recently planted vineyards, and damage is less significant on vigorous vines over 10 years old. Leaf infestation is reported to have no economic effect on wine grapes, or on the quality and quantity of wine made from them (Strapazzon and Girolami, 1985b; Strapazzon et al., 1986). In California in the early 1980s, large populations of V. vitifoliae were detected in grapevines grafted on 'AxR#1' (a hybrid between V. vinifera and V. rupestris). The existence of a different biotype (biotype B), having a greater parasitic ability on this rootstock, was demonstrated (Granett et al., 1985). These susceptible vineyards had to be uprooted, fumigated and replanted at a cost of over US$500 million (Chiarappa and Buddenhagen, 1994). In general, rootstocks with no vinifera parentage have retained their resistance remarkably, for over 120 years (Grannet et al., 2001a). Problems are more likely on rootstocks like AXR#1, with vinifera, parentage, which are now best avoided. For more information, see Balachowsky and Mesnil (1935), Dominguez Garcia-Tejero (1957) and Rilling (1964).