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Title: Infectivity of Steinernema carpocapsae and S. feltiae to larvae and adults of the hazelnut weevil, Curculio nucum: Differential virulence and entry routes

Author
item BATALLA-CARRERA, LAI, LAIA - University Of Barcelona
item MORTON, ANA - University Of Barcelona
item Shapiro Ilan, David
item STRAND, MICHAEL - University Of Georgia
item GARCIA-DEL-PINO, FERNANDO - University Of Barcelona

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2014
Publication Date: 9/1/2014
Citation: Batalla-Carrera, Lai, L., Morton, A., Shapiro Ilan, D.I., Strand, M., Garcia-Del-Pino, F. 2014. Infectivity of Steinernema carpocapsae and S. feltiae to larvae and adults of the hazelnut weevil, Curculio nucum: Differential virulence and entry routes. Journal of Invertebrate Pathology. 46:281-286.

Interpretive Summary: The hazel nut weevil is a major pest of hazel nuts, particularly in Europe; hazel nut weevil is also closely related to other nut-attacking weevils such as pecan weevil. One environmentally sound approach to controlling these weevils is the use of beneficial nematodes. Beneficial nematodes, also called entomopathogenic nematodes, are small round worms that only attack insects and are safe to humans, plants, and the environment. In this study, the basis for differential susceptibility of the hazelnut weevil (Curculio nucum) to entomopathogenic nematodes was investigated. Specifically, the main route of entry of two nematode species was determined in larvae and adult insects, and the response of the insect immune was assessed. Results suggested that nematodes primarily entered adult insects and larvae through the anus. Larvae were more susceptible to the nematode called S. feltiae D114 than S. carpocapsae B14 and adults were highly susceptible to S. carpocapsae B14 while displayed low susceptibility to S. feltiae D114. Penetration rate correlated with nematode virulence. In contrast, we observed little evidence that hazelnut weevils mounted any immune response towards the nematodes. We conclude the differential susceptibility of hazelnut weevil larvae and adults primarily reflected differences in the ability of these two nematodes to penetrate into the insect. Understanding these dynamics of infection will increase our ability to target the hazel nut weevil with nematodes in a viable pest management strategy.

Technical Abstract: The hazel nut weevil, Curculio nucum, is a major pest of hazel nuts, particularly in Europe; hazel nut weevil is also closely related to other nut-attacking weevils such as pecan weevil (Curculio caryae). In this study, the basis for differential susceptibility of the hazelnut weevil (to entomopathogenic nematodes was investigated. Specifically, the main route of entry of the nematodes, Steinernema carpocapsae strain B14 and S. feltiae strain D114 was determined in larvae and adult insects, and the response of the host immune was assessed. Results suggested that nematodes primarily entered adult insects and larvae through the anus. Larvae were more susceptible to S. feltiae D114 than S. carpocapsae B14 and adults were highly susceptible to S. carpocapsae B14 while adults displayed low susceptibility to S. feltiae D114. Penetration rate correlated with nematode virulence. In contrast, we observed little evidence that hazelnut weevils mounted any immune response towards the nematodes. We conclude the differential susceptibility of hazelnut weevil larvae and adults primarily reflected differences in the ability of these two nematodes to penetrate into the host. Understanding these dynamics of infection will increase our ability to target the hazel nut weevil with nematodes in a viable pest management strategy.