Comparison of cultivars of ornamental crop Gerbera jamesonii on productionof spider mite-induced volatiles, and their attractiveness to the predatorPhytoseiulus persimilis

We investigated whether volatiles produced by spider mite-damaged plants of four gerbera cultivars differ in attractiveness to Phytoseiulus persimilis , a specialist predator of spider mites, and how the mite-induced odor blen ds differ in chemical composition. The gerbera cultivars differed in resist ance, as expressed in terms of spider mite intrinsic rate of population inc rease (r(m)). In order of increasing resistance these were Sirtaki, Rondena , Fame, and Bianca. To correct for differences in damage inflicted on the c ultivars, we developed a method to compare the attractiveness of the blends , based on the assumption that a larger amount of spider mite damage leads to higher attraction of P. persimilis. Spider mite-induced volatiles of cul tivars Rondena and Bianca were preferred over those of cultivar Sirtaki. Sp ider mite-induced volatiles of cultivars; Sirtaki and Fame did not differ i n attractiveness to P. persimilis, Sirtaki plants had a lower relative prod uction of terpenes than the other three cultivars. This was attributed to a low production of cis-alpha -bergamotene. trans-alpha -bergamotene, trans- beta -bergamotene. and (E)-beta -farnesene. The emission of (E)-beta -ocime ne and linalool was lower in Sirtaki and Fame leaves than in Bianca and Ron dena. The importance of these chemical differences in the differential attr action of predatory mites is discussed.