Phytophthora cinnamomi requires warm moist soils if it is to reproduce and spread. This limits its distribution in Tasmania to areas that are generally below about 700 m in altitude and prevents it affecting low rainfall areas such as the Tasmanian midlands. Cold soil conditions can also occur at altitudes below 700 metres where a dense forest canopy shades the ground. For this reason wet forest and rainforest communities are not susceptible to P. cinnamomi in their undisturbed state.
The vegetation types most affected in Tasmania are heathland, moorland, dry sclerophyll forest. These vegetation types occur within the climatically susceptible areas and contain susceptible plant species. Moorland and heathland communities are perhaps the most severely affected as many of the shrub species present in these communities are susceptible to P. cinnamomi.
The map below shows the locations of all sites where the presence of P. cinnamomi has been confirmed by laboratory analysis. There will be many other infested areas which have not been sampled. The size of the infested area or severity of infection will vary significantly from site to site and is not indicated.
Phytophthora cinnamomi Map
The route of the Lyell Highway from Derwent Bridge to Queenstown is clearly distinguishable on the map and indicates the role of road construction, maintenance and vehicles in the spread of P. cinnamomi. The South Coast Walking Track and Mt Graeme Walking Track at Freycinet, are examples of disease spread associated with walking tracks. The area of mining exploration activity south of Macquarie harbour is also shows widely distributed disease. On Schouten Island, disease symptoms cover extensive areas of the granite country. This remote part of the island has received very little visitation for many years. The extent of disease spread in these areas suggests that P. cinnamomi has been present for a very long time, potentially dating back to the early tin mining days. It is very likely P. cinnamomi was introduced in the early days of European settlement and was widesprea by the time it was first surveyed for in the early 1970s. Many tens of thousands of hectares of moorland and heathland in Tasmania are infested with P. cinnamomi.
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.