Agricultural fungicides inadvertently influence the fitness of Colorado potato beetles, Leptinotarsa decemlineata, and their susceptibility to insecticides

Abstract

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is an agricultural pest of solanaceous crops which has developed insecticide resistance at an alarming rate. Up to this point, little consideration has been given to unintended, or inadvertent effects that non-insecticide xenobiotics may have on insecticide susceptibility in L. decemlineata. Fungicides, such as chlorothalonil and boscalid, are often used to control fungal pathogens in potato fields and are applied at regular intervals when L. decemlineata populations are present in the crop. In order to determine whether fungicide use may be associated with elevated levels of insecticide resistance in L. decemlineata, we examined phenotypic responses in L. decemlineata to the fungicides chlorothalonil and boscalid. Using enzymatic and transcript abundance investigations we also examined modes of molecular detoxification in response to both insecticide (imidacloprid) and fungicide (boscalid and chlorothalonil) application to more specifically determine if fungicides and insecticides induce similar metabolic detoxification mechanisms. Both chlorothalonil and boscalid exposure induced a phenotypic, enzymatic and transcript response in L. decemlineata which correlates with known mechanisms of insecticide resistance.\n\nKey MessagesO_LIPrior-exposure to a fungicidal application changes the phenotypic response of Leptinotarsa decemlineata to the insecticide imidacloprid\nC_LIO_LIBoth a fungicide and insecticide application activates similar molecular mechanisms of detoxification in Leptinotarsa decemlineata\nC_LIO_LIFungicidal xenobiotics may contribute to insecticide resistance in Leptinotarsa decemlineata\nC_LI\n\nAuthor Contribution StatementJC, SS, CB, AH, and RG conceived and designed research. JC, AC, DA, TD, and BS conducted experiments. JC and AC analyzed data. JC and RG wrote the manuscript. All authors read and approved the manuscript.