CLONAL AND LEAF AGE VARIATION IN POPULUS PHENOLIC GLYCOSIDES, IMPLICATIONS FOR HOST SELECTION BY CHRYSOMELA-SCRIPTA (COLEOPTERA, CHRYSOMELIDAE)

Feeding and ovipostion preferences of adult cottonwood leaf beetles, Chrysomela scripta F., vary among leaf age classes and Populus clones. Phenolic glycoside profiles of different age classes from seven Populus, representing a range of preferences, were examined for salicin, salicortin, and tremulacin composition and concentration among leaf age classes, as measured by leaf plastochron index (LPI). For each clone, extracts from the most preferred leaf age class for both behaviors (LPI 3) and from a nonpreferred class (LPI 12) were examined. Significant differences in the concentrations of these glycosides were found both between leaf age classes and among clones. The LPI 12 leaves contained lower concentrations of all three glycosides than the LPI 3 leaves. Comparisons were made between feeding and oviposition preferences and glycoside content. These suggest that salicin and salicortin content do not negatively influence host selection but that tremulacin may negatively influence such behavior.