Larval diet prior to and following virus ingestion influences the efficacy of two nucleopolyhedroviruses in whitemarked tussock moth (Orgyia leucostigma) caterpillars

Abstract

AbstractFood quality can influence the performance of immature insects and their interactions with pathogens, such as viruses. In manipulative field studies, virus-free caterpillars of the whitemarked tussock moth (WMTM) (Orgyia leucostigma (Smith)) had higher survival, more female-biased sex ratios, and were larger when feeding on white birch (Betula papyrifera Marshall) versus balsam fir (Abies balsamea (Linnaeus) Miller) or red spruce (Picea rubens Sargent). Subsequent laboratory studies with two nucleopolyhedroviruses, derived from WMTMs and Douglas-fir tussock moths, indicated that caterpillars fed high quality food (i.e., artificial diet) prior to infection had less mortality associated with virus infection than those feeding on lower quality foliage (i.e., birch). In field studies, caterpillars fed birch following infection had significantly lower mortality than those feeding on relatively lower quality foliage (i.e., balsam fir). We postulate that higher nutritional quality in artificial diet relative to birch (previrus-ingestion nutrition) and in birch relative to balsam fir foliage (postvirus-ingestion nutrition) has a positive effect on the ability of tussock moth caterpillars to resist or recover from viral infections, although the specific mechanisms responsible for observed resistance remain unclear.