Starvation and imidacloprid exposure influence immune response by Anoplophora glabripennis (Coleoptera: Cerambycidae) to a fungal pathogen

Authors: FISHER, JOANNA - Cornell University; Castrillo, Louela; DONZELLI, BRUNO - Cornell University; HAJEK, ANN - Cornell University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2017
Publication Date: 5/17/2017
Citation: Fisher, J.J., Castrillo, L.A., Donzelli, B., Hajek, A.E. 2017. Starvation and imidacloprid exposure influence immune response by Anoplophora glabripennis (Coleoptera: Cerambycidae) to a fungal pathogen. Journal of Economic Entomology. 110(4):1451-1459. https://doi.org/10.1093/jee/tox124.
DOI: https://doi.org/10.1093/jee/tox124

Interpretive Summary: Fungal entomopathogens sometimes synergize with certain insecticides which results in accelerated host death in some insects. Using the Asian longhorned beetle, Anoplophora glabripennis, we investigated potential mechanisms in the synergy between the entomopathogenic fungus Metarhizium brunneum and the insecticide imidacloprid. We investigated whether starvation would have a similar impact as imidacloprid exposure on the mortality of fungal-inoculated beetles. Using quantitative real-time PCR to quantify fungal load in inoculated beetles we determined how starvation and pesticide exposure impacted the beetles’ ability to tolerate or resist a fungal infection. The effect of starvation and pesticide exposure on the immune responses of the beetles were also quantified. Starvation had a similar impact on the survival of M. brunneum-inoculated beetles compared to imidacloprid exposure. The synergy, however, is not completely due to starvation since imidacloprid reduced the beetles' immune response while starvation did not significantly reduce these immune responses. Our results suggest that there are multiple mechanisms involved in the synergy between M. brunneum and imidacloprid.

Technical Abstract: In several insect systems, fungal entomopathogens synergize with neonicotinoid insecticides which results in accelerated host death. Using the Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), an invasive woodborer inadvertently introduced into North America and Europe, we investigated potential mechanisms in the synergy between the entomopathogenic fungus Metarhizium brunneum Petch and the insecticide imidacloprid. A potential mechanism underlying this synergy could be imidacloprid’s ability to prevent feeding shortly after administration. We investigated whether starvation would have a similar impact as imidacloprid exposure on the mortality of fungal-inoculated beetles. Using quantitative real-time PCR to quantify fungal load in inoculated beetles we determined how starvation and pesticide exposure impacted the beetles’ ability to tolerate or resist a fungal infection. The effect of starvation and pesticide exposure on the encapsulation and melanization immune responses of the beetles were also quantified. Starvation had a similar impact on the survival of M. brunneum-inoculated beetles compared to imidacloprid exposure. The synergy, however, is not completely due to starvation since imidacloprid reduced the beetles’ melanotic encapsulation response and capsule area while starvation did not significantly reduce these immune responses. Our results suggest that there are multiple interacting mechanisms involved in the synergy between M. brunneum and imidacloprid.