CHEMICAL ECOLOGY OF COTTONWOOD LEAF BEETLE ADULT FEEDING PREFERENCES ON POPULUS

The effect of select Populus clones on adult cottonwood leaf beetle fe eding preferences was examined. Field-planted University of Washington poplar pedigree materials-parent clones ILL-129 (Populus deltoides) a nd 93-968 (Populus trichocarpa), F-1 clones 53-242 and 53-246, and 87 F-2 selections-were used. Both held cage feeding tests with parent and F-1 clones, and leaf disc feeding tests with all 91 clones were perfo rmed. Feeding stimulants on the leaf surface, long-chain fatty alcohol s and alpha-tocopherylquinone (alpha-TQ), and phenolic glycosides, tre mulacin and salicortin, were analyzed to correlate chemical abundance with cottonwood leaf beetle Chrysomela scripta adult feeding preferenc e. The beetles showed varied feeding preferences among parent clones, F-1 clones, and F-2 clones. Contents of alcohols, tremulacin, and sali cortin did not explain adult beetle feeding preference. Content of a-T Q on the leaf surface did explain the adult beetle feeding preference. The beetles preferred to feed on clones with alpha-TQ rather than clo nes without alpha-TQ. As the amount of alpha-TQ increased, the feeding preference increased, and then decreased as the amount of alpha-TQ in creased further.