Strategies Involved in the Location of Hosts by the ParasitoidAphidius erviHaliday (Hymenoptera: Braconidae: Aphidiinae)

A volatile kairomone emitted from lima bean plants (Phaseolus lunatus) infested with the spider miteTetranychus urticae, was collected on Tenax-TA and analyzed with GC-MS. Two components were identified as the methylene monoterpene (3E)-4,8-dimethyl-1,3,7-nonatriene and the methylene sesquiterpene (3E,7E)-4,8,12-dimethyl-1,3,7,11-tridecatetraene, respectively, after purification by preparative GC on a megabore column and recording of UV, IR, and [(1)H]NMR spectra. The response of two species of predatory mites towards the identified chemicals was tested in a Y-tube olfactometer. Four of the compounds tested, linalool (3,7-dimethyl-1,6-octadien-3-ol), (E)-β-ocimene [(3E)-3,7-dimethyl-1,3,6-octatriene], (3E)-4,8-dimethyI-1,3,7-nonatriene, and methyl salicylate attracted females ofPhytoseiulus persimilis. Linalool and methyl salicylate attracted females ofAmblyseius potentillae. The response ofA. potentillae to these two kairomone components was affected by the rearing diet of the predators in the same way as was reported for the response to the natural kairomone blend: when reared on a carotenoid-deficient diet, the predators responded to the volatile kairomone ofT. urticae, but when reared on a carotenoid-containing diet they did not. The identified kairomone components are all known from the plant kingdom. They are not known to be produced by animals de novo. In addition to biological evidence, this chemical evidence suggests that the plant is involved in production of the kairomone. Based on the present study and literature data on the response ofT. urticae to infochemicals, it is concluded that the kairomone component linalool is also a component of a volatile spider-mite dispersing pheromone.