Rate of spread of myrtle wilt disease in undisturbed Tasmanian rainforests

Summary

The long-term rate of spread of myrtle wilt disease was monitored in plots within undisturbed forests at six localities in Tasmania representing a range of rainforest types containing myrtle, Nothofagus cunninghamii. The incidence of myrtle wilt, indicated by trees showing evidence of attack by the mountain pinhole borer Platypus subgranosus, at the start of the monitoring period was 15.8–45.4% of standing trees across the range of sites. After 12–18 y, the incidence was 16.8–50.9%, representing an increase in myrtle wilt of 0.08–0.67% per year.

There was a significant effect of rainforest type on both disease incidence and the level of physical damage to myrtle trees (broken limbs and stem wounds), callidendrous rainforests having higher disease and damage levels than thamnic and implicate stands. The effect of altitude on disease incidence was also significant, with myrtle wilt levels being lower at higher altitudes.

The factors affecting the levels of myrtle wilt and the current significance of the disease in Tasmanian rainforests are discussed; disease levels recorded over the sampling period indicate a currently stable situation.

Keywords:

• wilts
• rain forests
• disease surveys
• disease prevalence
• spread
• myrtle wilt disease
• Nothofagus
• Tasmania