Effects of Gypsy Moth on Radial Growth of Deciduous Trees

Abstract

Abstract We investigated the effect of gypsy moth (Lymantria dispar L.) larval abundance on annual radial growth of preferred, intermediate, and avoided host trees: northern red oak (Quercus rubra L.), sugar maple (Acer saccharum Marsh.), and white ash (Fraxinus americana L.), respectively. Individual trees were surveyed for gypsy moth larvae from 1979 to 1992 in a chronically infested forest on a drought-prone site in southwestern Québec. Increment cores were collected from 156 oaks, 39 maples, and 39 ash, and annual radial growth indices from 1950 to 1992 were calculated for each species. Growth was corrected for the influence of climate using regression models. For red oak, the average number of gypsy moth larvae per tree explained 73% of the variance in growth not explained by climate. Sugar maple and white ash growth was not correlated with gypsy moth larval numbers. These results are consistent with gypsy moth host preferences and provide evidence that nonepidemic levels of gypsy moth larvae can have a significant negative effect on the radial growth of individual trees. For. Sci. 47(3):338–348.