|Jandricic, Sarah -|
|Filotas, Melanie -|
|Sanderson, John -|
Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2014
Publication Date: February 25, 2014
Citation: Jandricic, S.E., Filotas, M.J., Sanderson, J.P., Wraight, S.P. 2014. Pathogenicity of conidia-based preparations of entomopathogenic fungi against the greenhouse pest aphids: green peach aphid, melon aphid, and foxglove aphid. Journal of Invertebrate Pathology. 118:34-46. Interpretive Summary: The green peach aphid, foxglove aphid, and melon aphid are among the most important greenhouse pests in the U.S., U.K., and Canada and can co-infest crops in the same greenhouse. To address this problem, biological control agents with the capacity to control all species of this pest complex are needed. The common fungal pathogens Beauveria, Metarhizium, and Isaria species have relatively broad host ranges and therefore are strong candidates for biological control; however, strains of these pathogens currently registered for greenhouse pest control are not highly effective against aphids. In a series of laboratory assays, we screened more than 40 new fungal isolates against nymphs of the above-listed aphids. The assays identified a number of Beauveria and Metarhizium isolates with virulence comparable to strains of these fungi comprising currently registered biopesticides, but none was found with exceptionally high virulence against aphid pests. Additional tests showed that adult aphids are more susceptible than nymphs to fungal infection but confirmed that infection has a limited pre-mortem effect on aphid reproduction. These results indicate that additional research into methods of improving control with existing biopesticide products and continued development of new products will be needed to make entomopathogenic fungi successful components of integrated pest management programs for aphids in greenhouses.
Technical Abstract: Seeking new isolates of entomopathogenic fungi with greater virulence against greenhouse aphid pests than those currently registered in North America for control of these insects, single-dose screening assays of 44 selected fungal isolates and 4 commercially available strains were conducted against first-instar nymphs of Myzus persicae and Aphis gossypii. Given the objective of identifying fungi highly virulent against aphids, original association with aphids or other hemipteran hosts was an important criterion in selection of the screened isolates. The assays identified a number of Beauveria and Metarhizium isolates with virulence equal to or greater than that of the commercial strains against the nymphal aphids, but none exhibited exceptionally high virulence. Virulence of Isaria isolates was unexpectedly low (less than 31 percent mortality at doses greater than 1000 conidia/millimeters squared). In dose-response assays, Beauveria ARSEF 5493 proved most virulent against M. persicae and A. gossypii; however, LC50s of this isolate did not differ significantly from those of B. bassiana commercial strain JW-1. Dose-response assays were also conducted with Aulacorthum solani, the first reported evaluations of Beauveria and Metarhizium against this pest. The novel isolate Metarhizium 5471 showed virulence greater than or equal to that of Beauveria 5493 in terms of LC25 and LC50, but 5493 produced a steeper dose response (slope). Additional tests showed that adult aphids are more susceptible than nymphs to fungal infection but confirmed that infection has a limited pre-mortem effect on aphid reproduction. Effects of assay techniques and the potential of fungal pathogens as aphid-control agents are discussed.