Relationships between plant pathogenic fungi and mites in vineyards: implications for IPM

In this paper we summarize the results of studies aimed at investigating the relationships between fungal diseases and mites occurring in European vineyards. Most of the data originated from observations carried out in commercial and experimental vineyards in north-eastern Italy. Grapevine downy mildew, Plasmopara viticola, and grape powdery mildew, Uncinula necator, are the most significant grape diseases in several viticultural areas in Europe and throughout the world. The spread of downy mildew in European vineyards may increase the abundance of some species of Phytoseiidae and Tydeidae. Amblyseius andersoni responded clearly to the spread of downy mildew symptoms, an effect also observed, but at lower magnitudes, for Typhlodromus pyri and Kampimodromus aberrans. The beneficial effect of downy mildew on the survival, development and reproduction of phytoseiids and tydeids has a clear impact on their population dynamics. Downy mildew effects varied among phytoseiids, being more relevant for A. andersoni than for T. pyri. These interactions may have implications for IPM because T. pyri is more effective than A. andersoni in controlling phytophagous mites in vineyards. The role of powdery mildew as a food source for A. andersoni and T. pyri was less pronounced than that of downy mildew. The capacity of generalist predatory mites to persist in perennial ecosystems contributes to the successful biological control of phytophagous mites. In vineyards, the persistence of generalist predators in the absence of prey may be improved by their feeding on various food sources. Pollen is probably the most important food source in spring and early summer, whereas mildews increase in importance in late summer. Predatory mite persistence is largely affected by pesticide use. The results of our studies showed that downy mildew availability mediates the effects of fungicides on predatory mites because it represents an alternative food for them. Moreover, downy mildew can enhance the recovery of predatory mite populations after pesticide applications.