EFFECTS OF CO2-MEDIATED CHANGES IN PAPER BIRCH AND WHITE-PINE CHEMISTRY ON GYPSY-MOTH PERFORMANCE

We examined the effects of CO2-mediated changes in the foliar chemistr y of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown un der ambient or enriched CO2 conditions, and foliage was subjected to p lant chemical assays and insect bioassays. Enriched CO2 atmospheres re duced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations were not mar kedly altered by CO2 environment. Gypsy moth performance was significa ntly affected by CO2 level, species, and the CO2 x species interaction . Under elevated CO2 conditions, growth was reduced for larvae fed bir ch, while development was prolonged for larvae fed pine. Although gyps y moths performed better overall on birch than pine, birch-fed larvae were influenced more by CO2-mediated changes in host quality.