Can alternative foods availability influence the impact of pesticides on predatory mites?

Generalist predatory mites belonging to the Phytoseiidae are important biocontrol agents in several perennial cropping systems. These predatory mites can persist for long periods on plants without prey, feeding on alternative foods included polle n and fungi. Predatory mite population are often limited by pesticide applications and these effects can be influenced by environmental factors such as the availability of alternative food sources. On grapevine, predatory mite abundance can be influenced by the spread of pathogens (e.g., grape downy mildew). Thus different grape downy mildew infection levels induced by different fungicide strategies can result in significant (indirect) effects on predatory mite populations. These effects can be stronger than those associated to the intrinsic toxicity of pesticides. On apple, the availability of alternative food sources (i.e., pollen) can mitigate the impact of insecticides on predatory mites. The provision of uncontaminated fresh pollen is likely to decrease pesticide exposure, and provides a highly nutritional food source that boosts mites’ fecundity, favoring the resilienc e of phytoseiid populations on treated plants.