Hormetic effect induced byBeauveria bassianainMyzus persicae

Abstract

ABSTRACTMyzus persicae, a serious sap-sucking pest of a large variety of host plants in agriculture, is traditionally controlled using chemical insecticides but there is interest in using biopesticides as restrictions are increasingly placed on the use of broad-spectrum pesticides. Here we show that in petri dish experiments high concentrations of the fungal entomopathogenBeauveria bassiana(strain PRRI 5336) lead to rapid mortality ofM. persicaebut at a low concentration (1 × 104conidia mL−1) there is a hormetic effect where longevity and fecundity are enhanced. Hormetic effects persisted across a generation with reduced development times and increased fecundity in the offspring ofM. persicaeexposed toB. bassiana. Whole plant experiments point to a hormetic effect being detected in two out of three tested lines. The impact of these effects might also depend on whetherM. persicaewas transinfected with the endosymbiontRickettsiella viridis, which decreases fecundity and survival compared to aphids lacking this endosymbiont. This fecundity cost was ameliorated in the generation following exposure to the entomopathogen. WhileB. bassianais effective in controllingM. persicaeespecially at higher spore concentrations, utilization of this entomopathogen requires careful consideration of hormetic effects at lower spore concentrations, and further research to optimize its application for sustainable agriculture is recommended.AUTHOR SUMMARYBiopesticides such asBeauveria bassianacan be effective alternatives to chemical insecticides to control insect pests. We tested the efficacy of this biopesticide against the important agricultural pest aphidMyzus persicaein laboratory experiments. We also tested whether the potential biological control agent and endosymbiontRickettsiella viridiscould provide protection against mortality caused byB. bassiana. While high doses ofB. bassianacaused rapid mortality in aphids, low doses enhanced aphid fecundity and survival. This enhancement persisted into the next generation, with shortened development times and increased fecundity regardless, even when high doses were used in the previous generation. The endosymbiontR. viridisdid not provide clear protection againstB. bassiana, in contrast to previous studies in other aphid species, but beneficial effects at low doses also occurred in this aphid line. We also observed hormesis on experiments on whole plants, but only for some aphid genotypes. To a lesser extent, we also observed beneficial effects of low doses ofB. bassianain experiments on whole plants, but only in some aphid genotypes. Fitness enhancement by biopesticides at low doses raises concerns for field applications but further research is required to understand its underlying mechanisms.