Biological control of spider mites in North-Italian vineyards using pesticide resistant predatory mites

Abstract

The success of phytoseiid mite releases to control spider mites [Eotetranychus carpini (Oudemans) and Panonychus ulmi (Koch)] on grapevines can be influenced by pesticide use and competition with local predatory mites. In field experiments we evaluated the effect of the release of Kampimodromus aberrans (Oudemans) and Typhlodromus pyri Scheuten strains showing field resistance to organophosphates and dithiocarbamates. Predatory mites were released in two vineyards infested by spider mites despite the occurrence of Amblyseius andersoni (Chant) and/or Phytoseius finitimus Ribaga. Single or mixed releases were planned. Spider mite populations were not effectively controlled by local predatory mites while successful control was achieved by released species. The effects of releases were higher in the second experimental year. In most cases A. andersoni densities were reduced by T. pyri and K. aberrans releases. Ph. finitimus suffered less than A. andersoni from intraguild predation. Among released species, the effect of the presence of a competitor was higher on T. pyri than on K. aberrans. Results suggest that the outcome of intraguild predation is prey-mediated. The equilibrium level between K. aberrans and T. pyri may depend on which spider mite species is the shared prey. The implications in management of spider mites on grapevines are discussed.