Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 14, 1998
Publication Date: N/A
Interpretive Summary: The Russian wheat aphid (RWA) is a worldwide pest of wheat and barley. It was first found in the United States in the mid-1980s. Since then, it has caused a combined direct and indirect economic impact in excess of $1 billion. The fungus Paecilomyces fumosoroseus has potential as a safe and effective biological control agent for this aphid, but information is needed about the mechanisms of infection. Different spore types of three strains of this fungus were tested in laboratory assays againist Russian wheat aphids. Spores were tested following production in a liquid medium and compared to spores produced by a standard, aerial production method. All spore types readily infected aphids in laboratory assays. These results will facilitate development of efficient large-scale production methods for this fungus.
Technical Abstract: The Russian wheat aphid, Diuraphis noxia, is a world-wide pest of wheat and barley. It was accidentally introduced into the United States in 1986 and since then has caused an accumulated impact of nearly $1 billion. The object of this study was to compare the efficacy for adult aphids of Paecilomyces fumosoroseus conidia of three strains produced on soild and liquid substrates. Preparations tested included aerial conidia produced on SDAY amd three preparations of spores grown in a liquid amino-acid-glucose- salts medium: freshly harvested spores, freeze-dried spores, and spores dried in air with the addition of a filtration agent. Spore suspensions were sprayed on aphids at a concentration of approximately 50 spores/sq cm. Mortality of aphids after 5 days was compared after adjusting the number of CFUs obtained for each preparation. Mortality indices were estimated in relation to aerial conidia of a standard isolate. There were no significant tdifferences among spore preparations for aphid survival time or mortality index. This study demonstrates that spores P. fumosoroseus produced culture are as efficacious as aerial conidia against the Russian wheat aphid.