In a series of laboratory tests, Russian wheat aphids, Diuraphis noxia (Mordvilko), responded to synthetic aphid alarm pheromone, (E)-β-farnesene, by removing stylets and leaving feeding sites or by crawling out of test arenas. Late instars and adults were more responsive than early instars. In dose-response assays, EC50 estimates ranged from 0.94 to 8.95 mg/ml among 3 experiments. In arenas, D. noxia also responded to the proximity of cornicle-damaged nymphs of either the green peach aphid, Myzus persicae (Sulzer), or of D. noxia, which suggests endogenous production of alarm pheromone by D. noxia. Combinations of (E)-β-farnesene and the aphid-pathogenic fungus Paecilomyces fumosoroseus (Wize) Brown & Smith did not enhance aphid mortality relative to controls treated with fungus only. Further studies involving appropriate formulations of (E)-β-farnesene are necessary before practical biorational strategies can be devised combining this semiochemical and biological control agent
