Role of leaf development and colour change in differential defoliation of Eucalyptus regnans families by the leaf eating beetle Chrysophtharta bimaculata (Olivier)

Open-pollinated families of Eucalyptus regnans, selected from a single provenance on their susceptibility to defoliation by the chrysomelid, Chrysophtharta bimaculata, were used to determine whether spring growth phenology (leaf numbers and leaf colour) was related to previously observed levels of defoliation. Families did not differ in numbers of leaves or leaf area produced per shoot. However, more susceptible families carried over 29% of their new foliage as red leaves during the period of maximum beetle activity; less susceptible families carried less than 20% of red foliage during the same period. Results were consistent across sites assessed in different years. The percentage of red leaves was strongly correlated with numbers of egg batches deposited and degree of subsequent defoliation. However as the egg lay did not occur when colour differences were evident, red foliage colour per se could not directly affect C. bimaculata host selection for oviposition.