Side Effects of Kaolin and Bunch-Zone Leaf Removal on Predatory Mite Populations (Acari: Phytoseiidae) Occurring in Vineyards

The effects of kaolin and bunch-zone leaf removal on populations of predatory mites Kampimodromus aberrans (Oudemans) and Typhlodromus pyri Scheuten were assessed in the context of four trials (2015–2016) carried out against Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae) in vineyards located in north-eastern Italy. Laboratory experiments were performed to evaluate the effects of kaolin on the survival and fecundity of K. aberrans and T. pyri populations originating from the same grape-growing area. In field trials, kaolin caused a gradual decrease in population density levels of both phytoseiid species (with the maximum reduction ranging from 49 to 91%) with a complete population recovery in the next spring. In laboratory experiments, kaolin was moderately harmful to both species, reducing their fecundity significantly (around 60%). Bunch-zone leaf removal determined lower phytoseiid populations in all trials, but this effect was significant only for K. aberrans in one of them. A limited use of kaolin and the adoption of bunch-zone leaf removal did not irreversibly affect phytoseiid populations in vineyards and thus can be considered compatible with IPM strategies.