A thirteen-year study on the impact of a severe canker disease of Corymbia calophylla, a keystone tree in Mediterranean-type forests

Worldwide, forests and woodlands have shown progressive declines in health as a result of global environmental changes in combination with local anthropogenic drivers. This study examined the incidence and progression of a canker disease of marri ( Corymbia calophylla) caused by the endemic fungal pathogen Quambalaria coyrecup at three paired forest and anthropogenically disturbed sites in the southwest of Western Australia over 13 years. At the time of plot establishment in 2001, cankers were present on trees at all six sites with 22.7% of the assessed trees cankered. By 2014, cankers had led to the death of 6.7% of the trees, and an additional 10.0% of the trees developed cankers during this time. A further 2.3% of trees died due to causes other than canker, resulting in a final figure of 65.0% of trees remaining alive and free of cankers for the duration of the survey period. Canker incidence was significantly greater on trees present at anthropogenically disturbed sites ( along roadsides and in paddocks) than forest trees ( 35.3% increasing to 50.7%, 10.0% increasing to 14.7%, respectively). Trunk diameter at breast height, tree height and crown ratings were not correlated with canker presence. This long-term study provides evidence of the increasing severity of this canker pathogen and the impact it is having on the survival of marri.