The cabbage looper, Trichoplusia ni, a global generalist lepidopteran pest, has developed resistance to many synthetic and biological insecticides, requiring effective and environmentally acceptable alternatives. One possibility is the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). This baculovirus is highly infectious for T. ni, with potential as a biocontrol agent, however, its effectiveness is strongly influenced by dietary context. In this study, microscopy and transcriptomics were used to examine how the efficacy of this virus was affected when T. ni larvae were raised on different diets. Larvae raised on potato host plants had lower chitinase and chitin deacetylase transcript levels and thickened, multilayered peritrophic membranes than those reared on either cabbage or artificial diet. These changes help explain the significantly lower susceptibility of potato reared individuals to baculovirus, underlining the importance of considering the dietary influences on insect susceptibility to pathogens when applying biological control agents in integrated pest management strategies
