Role of Tree Trunks, Foliage Type, and Canopy Size in Host Selection by Lymantria dispar (Lepidoptera: Lymantriidae)

Abstract

In caged choice experiments, Lymantria dispar (L.) larvae strongly preferred Acer saccharum Marsh. and Fraxinus pennsylvanica Marsh. trunks (44.3 and 43.3% of larvae, respectively) to Betula papyrifera Marsh. trunks (5.7%). When larvae were allowed to choose among the foliage of live seedlings of the same species, they preferred B. papyrifera (71.0%) over A. saccharum (14.3%) and F. pennsylvanica (0.7%). Trunk sections of A. saccharum and B. papyrifera were wrapped around live seedlings of the same trees and F. pennsylvanica in six possible combinations of trunk and foliage species to evaluate the impact of trunk characteristics on host selection in the presence of foliage. The most preferred trunk-foliage combinations, in descending order of percentage larvae found on each, were as follows: A. saccharum-B. papyrifera (41.0%), B. papyrifera-B. papyrifera (19.0%), A. saccharum-A. saccharum (14.8%), B. papyrifera-A. saccharum (12.2%), A. saccharum-F. pennsylvanica (2.2%), and B. papyrifera-F. pennsylvanica (1.0%). Both trunk species and foliage species Significantly influenced larval choice. The effect of tree canopy size, as measured by leaf surface area, on the distribution of larvae was measured in a forest clearing where five replications of 17 tree species and cultivars were planted. The tree species ranged from highly susceptible ( Malus sp.) to highly resistant ( Gleditsia triacanthos L.). The number of larvae per tree was explained well by the size of the leaf canopy for the six most preferred tree species and cultivars. This relationship did not exist for the remaining 11 species and cultivars of less preferred trees. Apparently, the size of preferred trees influences the distribution of gypsy moth larvae among them.