Does windborne pollen mediate the effects of pesticides on predatory mites?

Generalist predatory mites belonging to the family Phytoseiidae can persist in European apple orchards when prey is scarce by feeding on pollen and other alternative foods. It has been reported that grass management can affect pollen availability on apple leaves with implications for phytoseiid persistence. The use of pesticides is a major factor affecting phytoseiid abundance in apple orchards. In this study we compared the effects of a number of pesticides on populations of Kampimodromus aberrans in two apple orchards with a different grass management, i.e. a high or a low grass mowing frequency. Reducing grass mowing frequency resulted in higher predatory mite numbers probably because of a higher pollen availability on apple leaves. A laboratory study was planned to demonstrate the role of pollen vailability in mediating interactions between pesticides and phytoseiids.