Phytophthora cinnamomi requires warm moist soils if it is to reproduce and spread. This limits its distribution in Tasmania. It generally is found below 700 m altitude, however in areas of recent ground disturbance it can cause Phytophthora dieback at altitudes of up to 1000 m. It is generally absent from low rainfall areas such as the Tasmanian midlands.
Due to the need for warm soils Phytophthora dieback is not generally an issue in Tasmania where there is dense shading of the ground, therefore communities such as wet forests and dense scrubs are often considered to not be susceptible.
Outside of high altitude and wet forests areas Phytophthora dieback is very widespread but generally localised in Tasmania. It is however largely restricted to areas of past or present human activity. Historical mining and prospecting activities appear to have contributed significant to the spread, whilst roading and development have contributed and walking tracks are often gateways for Phytophthora dieback in more remote areas. The size of infections or severity of infections will varies significantly from area to area.
Within this matrix of infested sites around Tasmania, significant areas still remain free of infestation e.g. Maria Island, parts of the South West National Park and many small catchments on the east and north coasts.
statewide map of phytophthora isolations - 2025