The influence of the jarrah leafminer Perthida glyphopa Common (Lepidoptera: Incurvariidae) and prescribed burning on the girth increment of jarrah Eucalyptus marginata Donn ex Smith

Girth increment in jarrah trees, E. marginata, both resistant and susceptible to the jarrah leafminer, P. glyphopa, was measured at 3 sites between 1971 and 1986 and at another site between 1971 and 1981. Significant annual losses of girth increment were detected in the susceptible trees damaged by the leafminer before and during the time of observation. In trees observed through the development of heavy infestation, significant girth increment losses occurred some 5 years after the damage began. Over the period of observation the mean losses of girth increment in the susceptible trees ranged from 44 to 70%.

Rainfall in both current and preceding years had a significant effect on the girth increment in all trees, but varied between sites. At the drier sites both resistant and susceptible trees responded significantly only to the current year's rainfall, while those at the wetter sites were significantly influenced by rainfall of the previous year. In the susceptible trees this effect was overridden by the influence of damage by the leafminer. Girth increment in both resistant and susceptible trees increased for 1 year after 4 out of 5 ground fires in spring that occurred during the time of observation.