The Activity of the Phytochemical Defenses of Red Maple (Acer Rubrum L.) And Sugar Maple (Acer Saccharum Marsh.) Against the Forest Tent Caterpillar (Malacosoma Disstria Huebner)

Abstract

The forest tent caterpillar (Malacosoma disstria Hubner) is a serious economic pest of many deciduous trees throughout North America. This insect avoids the foliage of red maple (Acer rubrum L.). An investigation of the phytochemical activity of the foliage of A. rubrum against the forest tent caterpillar (FTC) was undertaken. It was discovered that the foliage of sugar maple (Acer saccharum Marsh.), generally considered to be a food host of the FTC, could also contain secondary chemicals that harm this insect. When fed foliage of both maples, the FTC grew at a significantly reduced rate than those larvae that were fed the foliage of the preferred host, trembling aspen (Populus tremuloides Michx). All larvae fed red maple were dead within two weeks. The primary mode of action of sugar maple was one of internal toxicity (growth inhibition) whereas red maple was severely antifeedant and possibly also internally toxic. Feeding bioassays with extracts and purified compounds from the maples incorporated into artificial diet at sub-ecological levels, revealed that both species are chronically toxic and cause concentration-dependent reductions in larval growth and pupal weight, and increases in larval mortality. An increase in the time needed to reach pupation and adulthood for males in the red maple treatment was also observed. The extract of A. saccharum leaves was actually more active against the forest tent caterpillar than was the species of maple that the insect always avoided. A study of the variability of the maple defensive phytochemicals showed that although some variation in anti-FTC activity between different growing sites and within individual trees from the same growing site existed, it was not great enough to support the hypothesis that certain sugar maple trees possessed relatively lesser phytochemical defenses. (Abstract shortened by UMI.)