Behaviour and biological control of two-spotted spider mite (Tetranychus urticae) in floricane red raspberry plantations

The biology, behaviour and reciprocal relationships of Tetranychus urticae, Neotetranychus rubi and the phytoseiid mite Amblyseius andersoni were investigated from 1999 to 2007 on floricane red raspberry in Trentino, Northern Italy. From 2005 to 2007, in a plantation in Mocheni’s Valley the efficiency against two-spotted spider mite of an A.andersoni local strain and the commercially available predators Amblyseius californicus and Phytoseiulus persimilis was also evaluated. Two introduction rates (26 and 52 individuals/m, equivalent to 10.4 and 20.8 individuals/m2) at different times of release were compared for these two last predators. A. californicus releases, applied before the middle of June, were more effective than late releases in every year, in comparison with check plots (no release). The best control result was recorded where the highest dose was introduced. However, A. californicus didn’t perform as well as A. andersoni in the reintroduction plot. In our trials, P. persimilis established in the crop with very small populations, probably indicating important ecological requirements (prey density, release rate, climate under polyethylene rain covers, etc.) for its establishment. The information we collected was used to produce a two-spotted spider mite management recommendation scheme for Trentino’s raspberry growers.