Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2004
Publication Date: April 1, 2005
Citation: Yee, W.L., Lacey, L.A. 2005. Mortality of different life stages of Rhagoletis indifferens (Diptera: Tephritidae) exposed to the entomopathogenic fungus Metarhizium anisopliae. Journal of Entomological Sciences. 40(2):167-177. Interpretive Summary: The western cherry fruit fly is the most serious pest of cherries in the Pacific Northwest of the U.S. USDA personnel at the Yakima Agricultural Research Laboratory in Wapato, WA, conducted a study to determine the effects of the fungus Metarhizium anisopliae on mortality of flies. Adult flies emerging from soil were infected, with 30-60% infection and death rates. Adults caught in trees and exposed to the fungus were also infected and suffered 100% mortality at the higher concentrations. Larvae exposed to treated soil were not infected. The results of this study are important in that they indicate the fungus has potential to be a control agent of the fly stage in soil, but that more virulent isolates are needed before practical control of the fly using the fungus can be considered.
Technical Abstract: Effects of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin on the mortality of different life stages of the western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), were determined in laboratory tests. When teneral adults were exposed to fungal spores mixed in soil (7.63 x 105 and 1.61 x 106 spores/g) or applied to the surface of soil (1.14 x 106 and 2.28 x 106 spores/cm2) with 13 to 30% moisture, adult emergence was not reduced, but 11 to 68% of emerging adults were infected at death. When adult flies were exposed to various concentrations of dry spores inside vials, 15 mg (4.59 x 108 spores/10 flies) was the lowest needed for 100% mortality at 7 d post exposure, and resulted in 6.0 x 106 spores adhering to each fly. Females exposed to 1.8 mg (5.51 x 107 spores/10 flies) laid as many eggs as control females between 0 and 3 d post exposure, but due to mortality infected flies laid fewer eggs between 3 and 7 d. Third-instar larvae exposed to treated soil (9.63 x 104 to 4.81 x 106 spores/cm2) with 20% moisture were not infected.