Fungal pathogen and ethanol affect host selection and colonization success in ambrosia beetles

Authors: RASSATI, DAVIDE - Universita Di Padova; CONTARINI, MARIO - University Of Tuscia; Ranger, Christopher; CAVALETTO, GIACOMO - Universita Di Padova; ROSSINI, LUCA - University Of Tuscia; SPERANZA, STEFANO - University Of Tuscia; FACCOLI, MASSIMO - Universita Di Padova; MARINI, LORENZO - Universita Di Padova

Submitted to: Agricultural and Forest Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2019
Publication Date: 8/1/2019
Citation: Rassati, D., Contarini, M., Ranger, C.M., Cavaletto, G., Rossini, L., Speranza, S., Faccoli, M., Marini, L. 2019. Fungal pathogen and ethanol affect host selection and colonization success in ambrosia beetles. Agricultural and Forest Entomology. 22(1):1-9. https://doi.org/10.1111/afe.12351.
DOI: https://doi.org/10.1111/afe.12351

Interpretive Summary: Ambrosia beetles exhibit broad host ranges, but a relatively narrow preference based on condition of the host tissue. Pathogen-infected host tissues, and tissues containing ethanol, can initiate attacks by ambrosia beetles, but few studies have determined how these factors interact and influence colonization success. Our first objective was to examine how logs infected with a fungal pathogen (Cryphonectria parasitica) and treated with ethanol affected ambrosia beetle selection. Our second objective was to assess how logs soaked in different ethanol concentrations influenced ambrosia beetle selection and colonization success. Logs infected by C. parasitica were more attractive than uninfected logs to the ambrosia Anisandrus dispar (Fabricius). Ethanol-soaked logs were also more attractive than ethanol-baited logs or untreated logs. Increasing ethanol concentrations in host tissues was differentially attractive to X. saxesenii and X. germanus. Overall, these results indicate pathogen-infection and the presence of ethanol affect both host selection and colonization success of ambrosia beetles, but this effect varies among species.

Technical Abstract: Opportunistic ambrosia beetles exhibit broad host ranges, but a relatively narrow preference based on condition of the host tissue. Pathogen-infected host tissues, and tissues containing ethanol, can initiate attacks by ambrosia beetles, but few studies have determined how these factors interact and influence colonization success. Our first objective was to examine how logs infected with a fungal pathogen (Cryphonectria parasitica) and treated with ethanol (i.e., baited with ethanol lure, soaked in ethanol, or untreated) affected ambrosia beetle selection and colonization success. Our second objective was to assess how logs soaked in different ethanol concentrations ranging from 3–12.5% influenced ambrosia beetle selection and colonization success. Logs infected by C. parasitica were more attractive than uninfected logs to the native ambrosia Anisandrus dispar (Fabricius). Ethanol-soaked logs were also more attractive than ethanol-baited logs or untreated logs, but the difference among these treatments was more evident in uninfected than infected logs. Increasing ethanol concentrations in host tissues was differentially attractive to X. saxesenii and X. germanus. A nonlinear relationship was also documented between concentration of ethanol used for soaking logs and emergence of X. germanus adults. Overall, these results indicate pathogen-infection and the presence of ethanol affect both host selection and colonization success of ambrosia beetles, but this effect varies among species. This contrasting response could be a niche-partitioning mechanism based on ethanol within host tissues.