Submitted to: Journal of Chemical Ecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/28/1998
Publication Date: N/A
Citation: Interpretive Summary: Poplar trees are grown throughout the world for short rotation production of woody pulp materials which are used in paper manufacturing and in generating ethanol fuel. Poplars are easy to grow and breed, and most natural populations have excellent growth characteristics. One limiting factor for poplar crops is the severe defoliation from feeding activity of the cottonwood leaf beetle. Beetle feeding often results in stunted growt of the trees and thus lowers the recovery of woody pulp. Leaf surface chemicals of poplars are known to be involved in the stimulation of beetle feeding on foliage. The compounds were identified as alfa- tocopherylquinone (a compound related to Vitamin E) and several alcohols. Combined, these compounds synergistically stimulate cotton leaf beetle feeding in laboratory feeding bioassays. The objective of this research was to evaluate the variation in amounts of poplar leaf surface chemicals and associate the chemicals with beetle feeding. The results show that variation occurs in the leaf surface chemicals of selected poplar trees and that beetles do not feed on trees when alpha tocopherylquinone is absent from the leaf surface. Through breeding selection, as shown in this study, we can remove the feeding stimulants, improve poplar resistance to cottonwood leaf beetles, and increase the availability of woody pulp materials for alcohol manufacturing. Use of beetle resistant trees also will result in less need for insecticide treatment and lower rates of pollution from insecticides. Decreased use of insecticides will benefit farmers by reducing their expenses for pest management and the general United States population will benefit by having a healthier and cleaner environment.
Technical Abstract: Field planted University of Washington poplar pedigree materials, parent clones ILL-129, Populus deltoides, 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 alpha-tocopherylquinone (alfa-TQ), and phenolic glycosides, tremulacin and salicortin, were analyzed to correlate chemical abundance with cottonwood leaf beetle, Chrysomela scripta Fabr. (Coleoptera: Chrysomelidae) 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 alpha-TQ on the leaf surface could explain the adult beetle feeding preference. The beetle preferred to feed on the clones with alfa-TQ. Low amounts of alpha-TQ in leaves stimulated beetle feeding, but higher amounts of alpha-TQ caused a decrease from peak beetle feeding activity.