We investigated the effects of paper birch (Betula papyrifera Marshall) condensed tannin on the performance of whitemarked tussock moth (Orgyia leucostigma J. E. Smith) larvae. Laboratory bioassays were conducted on fifth stadium larvae. Larvae were reared on one of three artificial diets: control (no condensed tannin), moderate condensed tannin (8.8% dry mass), and high condensed tannin (17.6% dry mass). Larvae fed tannin-amended diets exhibited increased stadium duration, decreased relative growth rate (RGR), and decreased food conversion efficiencies. Larvae compensated for low consumption and growth rates by prolonging development times such that insects on tannin diets ate more and grew larger than insects on the control diet. We analyzed tannin levels in food, frass, and body tissue and found evidence that larvae do not metabolize condensed tannin, but concentrate and egest it. This research demonstrates that paper birch condensed tannin has both positive and negative effects on the performance of tussock moth larvae. However, whether the risks of increased development time and prolonged exposure to natural enemies are balanced out by the benefit of increased final size (and possibly fecundity) remains unclear.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA