Variation in insect damage and growth in Eucalyptus globulus
Objectives of this study were to examine (i) between-provenance variation in susceptibility to insects in Eucalyptus globulus and (ii) relationships between insect damage and tree growth. We planted seedlings of 18 provenances of E. globulus from south-east Australia in a field trial and measured tree growth and insect damage.
Christmas beetles Anoplognathus spp. were the dominant herbivores during this experiment, and 99% of trees were affected by them. Defoliation of individual trees by Anoplognathus spp. ranged from 0% to 85%.
The main results of this study were that: (i) provenances of E. globulus from Tasmania and the Bass Strait islands, which had previously shown resistance to autumn gum moth Mnesampela privata and leaf blister sawfly Phylacteophaga froggatti tended to be resistant to Anoplognathus spp.; (ii) mean tree volume was reduced by herbivory; and (iii) the volume-based performance ranking of provenances changed depending on the probability of insect outbreaks.
Fast-growing provenances should be planted in optimal growing areas for E. globulus with low probability of insect outbreaks. However, in suboptimal growing areas, planting slightly slower growing but more resistant provenances is likely to result in greater output than planting fast-growing provenances when the probability of insect outbreaks is high.