Responses of Russian wheat aphid (Homoptera : Aphididae) to aphid alarm pheromone

rn a series of laboratory tests, Russian wheat aphids, Diuraphis noxia (Mor dvilko), responded to synthetic aphid alarm pheromone, (E)-beta-farnesene, by removing stylets and leaving feeding sites or by crawling out of test ar enas. Late instars and adults were more responsive than early instars. In d ose-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 cornicl e-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)-beta-farnesene and the aphid pathogenic fungu s Paecilomyces fumosoroseus (Wize) Brown & Smith did not enhance aphid mort ality relative to controls treated with fungus only. Further studies involv ing appropriate formulations of (E)-beta-farnesene are necessary before pra ctical biorational strategies can be devised combining this semiochemical a nd biological control agents.