LIGHT ENVIRONMENT ALTERS RESPONSE TO OZONE STRESS IN SEEDLINGS OF ACER-SACCHARUM MARSH AND HYBRID POPULUS L .3. CONSEQUENCES FOR PERFORMANCE OF GYPSY-MOTH

Both light conditions and ozone fumigation alter the chemical composit ion of tree foliage and are thus likely to influence tree-insect inter actions. We investigated the direct and interactive effects of light e nvironment and ozone exposure on the performance of gypsy moth (Lymant ria dispar L.) larvae reared on hybrid poplar (Populus tristis Fisch. x P. balsamifera L. cv. Tristis) and sugar maple (Acer saccharum Marsh .). We used a split-plot experimental design (light nested within ozon e) and fourth-instar bioassays to calculate standard indices of insect growth and feeding performance. For insects fed poplar, consumption, growth and processing efficiencies were affected more by light environ ment than by ozone. Larvae ate and grew less on high-light foliage, re sponses attributable to higher levels of phenolic glycosides in those leaves. For insects fed maple, no significant effects of light, ozone, or light x ozone were observed. These results demonstrate that light environment and ozone pollution can alter the dynamics of interactions between trees and associated insects and that responses are species-s pecific.