Grape downy mildew Plasmopara viticola, an alternative food for generalist predatory mites occurring in vineyards

The persistence of generalist predatory mites in scarcity or absence of prey is a requirement for successful biocontrol of herbivore mites. Pollen is an alternative food for generalist predatory mites. However, the presence of pollen in vineyards is often limited and thus other food sources should contribute towards generalist predatory mite persistence. Relationships between the population increases of generalist phytoseiids with late-season spread of grape downy mildew (GDM) Plasmopara viticola have been reported. We testest the hypothesis that GDM could be a suitable food for the predatory mites Amblyseius andersoni and Typhlodromus pyri. We compared the development times, oviposition rates and life-table parameters of predatory mites feeding on pollen or GDM in the laboratory. GDM supported the survival, development and oviposition of T. pyri and A. andersoni. GDM was a less suitable food source than pollen for both phytoseiid species and was more favorable for A. andersoni than for T. pyri. Implications for conservation biological control in vineyards are discussed.