THE ROLE OF ALTERNATIVE FOOD AND MICROCLIMATE IN THE SYSTEM TYPHLODROMUS-PYRI SCHEUTEN (ACARI, PHYTOSEIIDAE) - PANONYCHUS-ULMI KOCH (ACARI, TETRANYCHIDAE) ON GRAPE VINES .1. LABORATORY INVESTIGATIONS

The nutritional value of different food resources for T. pyri occurring on grape vines was tested in feeding experiments. Development and reproduction of the predacious mite were the criteria being studied. The majority of the offered pollen species proved to be of nutritional value to the mites. Pollen from trees and grasses that flower in spring had the best nutritional quality. Pearl hairs from grape leaves and larvae of Drepanothrips reuteri also allowed the reproduction of T. pyri. The most favourable types of food were, however, the eriophyid mites Calepitrimerus vitis and Eriophyes vitis. Panonychus ulmi was of a considerably lower nutritional value. This spider mite was barely accepted by juvenile predacious mites, but also only reluctantly fed upon by adult mites. Tetranychus urticae, on the other hand, was readily accepted. In dual-choice tests, those kinds of food were always preferred which had performed best in the feeding experiments. Electrophoretic analysis of the gut contents of predatory mites, which had been collected in vineyards, showed that pollen from different wind-pollinating species constituted the major part of the predatory mite's diet during the first part of the vegetation period. During the summer, T. pyri fed mainly on eriophyid mites and thrips larvae, if present. Spider mites constituted the major part of the diet from August to the end of the vegetation period.