Chemical Ecology of Cottonwood Leaf Beetle Adult Feeding Preferences on Populus

Abstract

The effect of select Populus clones on adult cottonwood leaf beetle feeding preferences was examined. Field-planted University of Washington poplar pedigree materials—parent clones ILL-129 (Populus delloides) and 93-968 (Populus trichocarpa), F1 clones 53-242 and 53-246, and 87 F2 selections—were used. Both field cage feeding tests with parent and F1 clones, and leaf disc feeding tests with all 91 clones were performed. Feeding stimulants on the leaf surface, long-chain fatty alcohols and α-tocopherylquinone (α-TQ), and phenolic glycosides, tremulacin and salicortin, were analyzed to correlate chemical abundance with cottonwood leaf beetle Chrysomela scripta adult feeding preference. The beetles showed varied feeding preferences among parent clones, F1 clones, and F2 clones. Contents of alcohols, tremulacin, and salicortin did not explain adult beetle feeding preference. Content of α-TQ on the leaf surface did explain the adult beetle feeding preference. The beetles preferred to feed on clones with α-TQ rather than clones without α-TQ. As the amount of α-TQ increased, the feeding preference increased, and then decreased as the amount of α-TQ increased further.