As of 2005, it was confined to a relatively small area of Cornwall but has also been found in Wales and Cheshire suggesting that the pathogen may be being spread by the horticultural trade. It grows optimally at 18°C and cannot grow above 26°C which suggests that it may have originated in a temperate climate, possibly in China, before being introduced to the UK. It is currently being controlled by culling Rhododendrons within diseased regions. In 2008, an infected Rhododendron ponticum was found in Ireland.
Another host is Bilberry (Vaccinium ssp.), with severe outbreaks in Staffordshire, England. In such cases, the disease is known as Bilberry Blight.