Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2001
Publication Date: 8/16/2001
Citation: Mesquita, A.L., Lacey, L.A. 2001. Interaction of the entomopathogenic fungus, Paecilomyces fumosoroseus (Deuteromycotina:Hyphomycetes) with the parasitoid, Aphelinus asychis (Hymenoptera:Aphelinidae) and their competition for an aphid host. Biological Control. 22:51-59. Interpretive Summary: Concerns over the cost and environmental impact of conventional control strategies and subsequent development of resistance to several insecticides in targeted species have prompted an increased interest in the integrated approach for management (IPM) of Russian wheat aphid. Biological control, including use of disease causing agents will play a large role in IPM. Because the Russian wheat aphid and other aphids obtain their food by piercing plant tissues rather than feeding on the surface of the leaves, fungi are the only effective disease causing agents used as biological control agents of this group of insects. Insect parasites are also used as biological control agents of Russian wheat aphid and other aphids. The fundamental questions we address are can these two groups of natural enemies be used against the same pest insect without antagonistic interference? Our research shows that parasitic wasps will avoid aphid hosts that have been exposed to lethal concentrations of fungus. Conversely, aphids that have been parasitized by the wasps do not become infected by the fungus. Our research demonstrates minimal interference between the fungus and parasite for the biological control of this important aphid pest.
Technical Abstract: The interaction between the fungus, Paecilomyces fumosoroseus, the Russian wheat aphid, Diuraphis noxia, and its common parasitoid, Aphelinus asychis, was investigated under laboratory conditions to determine if fungal infection of the aphid host had an effect on oviposition and feeding behavior of the female parasitoid and on development of parasitoid progeny. Parasitoid females spent considerably less time with their ovipositor inserted in dead aphids and aphids that had been exposed to P. fumosoroseus 72 h prior to contact with the parasitoids. The percentage of successfully parasitized D. noxia was significantly reduced as a function of the time between treatment with P. fumosoroseus and parasitoid oviposition. The number of mummies produced by two female A. asychis, during 24 h of exposure, varied from 20.3 to 23.0 and was not significantly different when the aphids were first exposed to the parasitoids, then treated with P. fumosoroseus 24, 48, 72 and 96 h after exposure. The percentage of emergence of the F1 generation of A. asychis was significantly lower among the aphids exposed to the parasitoid and treated with the fungus 24 h afterward, than for the untreated aphids. Various findings of this study demonstrate the potential of synergistic interaction of P. fumosoroseus and A. asychis for the biological control of D. noxia.