DAMAGE CAUSED BY INSECTS AND FUNGI TO EUCALYPT FOLIAGE - SPATIAL AND TEMPORAL PATTERNS IN MEDITERRANEAN FOREST OF WESTERN-AUSTRALIA

Damage sustained by leaves, of jarrah (Eucalyptus marginata Donn ex Sm .) ground coppice was studied in three regions of jarrah forest over 3 -6 years. After 12 months, it varied from 9 to 25% of leaf area and wa s mostly caused by insects (8-22%), particularly mining and chewing sp ecies. Damage caused by the pest insect species Perthida glyphopa Comm on and the fungus Mycosphaerella sp. was not strongly associated with any of ten environmental/stand variables measured. Comparisons of pole crowns and ground coppice showed only one consistent trend: Mycosphae rella fungus damaged leaves of ground coppice more than those of pole crowns. Two successive cohorts of leaves were studied for 39 and 51 mo nths; insect-related damage continued to increase over the half-life o f the jarrah leaf (24 months), despite a decline in concentration of f oliar nutrients within 3 months. Damage caused by Mycosphaerella fungu s occurred mostly during the first 2 months after leaf flush. Leaf abs cission differed between the two cohorts studied. The 1984 cohort show ed no difference when the wettest and driest plots were compared, wher eas for the 1985 cohort, plants in the driest plots shed significantly more leaves than those in the wettest plots. Low rainfall and high le vels of damage to leaves appeared to promote leaf abscission in this c ohort. We also compared damage sustained by jarrah leaves with the oth er seven eucalypt species present in State Forest near Manjimup. Jarra h had the highest overall damage. the highest level of insect damage a nd the second highest level of fungal damage. Data on N, K and P conce ntrations in new and mature leaves of these eucalypt species were not helpful in explaining the differences in damage levels between species . Averaging over all eight species, the proportion of leaf area damage d was 11.8%, comprising 7.4% from insects and 4.4% from fungus.Althoug h these averages conform with published values for eastern Australian eucalypts, this may be fortuitous because most studies have incorrectl y calculated average damage.