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, C hrysomela scripta F., vary among leaf age classes and Populus clones. Phenolic glycoside profiles of different age classes from seven Populu s, representing a range of preferences, were examined for salicin, sal icortin, and tremulacin composition and concentration among leaf age c lasses, as measured by leaf plastochron index (LPI). For each clone, e xtracts 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. C omparisons were made between feeding and oviposition preferences and g lycoside content. These suggest that salicin and salicortin content do not negatively influence host selection but that tremulacin may negat ively influence such behavior.