Native to the north western United States, the first UK case of Phytophthora pluvialis was found in Cornwall in October 2021. P. pluvialis is a fungus-like pathogen which affects a variety of trees but most commonly conifers such as pine, fir and spruce. Since October P. pluvialis has been found in other parts of Cornwall and in Devon, as well as a few isolated cases in the north of the country and Scotland, resulting in a demarcated area being drawn around areas known to be experiencing infections. The wood of trees infected with P. pluvialis cannot be removed from site or taken beyond the boundary of the demarcated area, and must instead be destroyed in situ. The current boundary of the demarcated area is shown below and can also be found HERE; if you are within this area or close to its borders it is worth regularly checking for any updates, as the boundaries are subject to change depending on the spread of the disease.
Map of the P. pluvialis demarcated zone provided by the Forestry Commission
Infected trees may show symptoms including the following:
Brown needles
Dieback in some or all limbs
Sticky, white, resinous cankers on shoots and twigs
Lesions in the bark at the base of the tree and on the tree trunk
If you notice that trees on your land are displaying symptoms of P. pluvialis, you must report the case using the TreeAlert tool created by Forest Research, which can be found HERE.
Further advice and guidance can be found at the following sources:
Symptom Guide provided by Forest Research, including photographs
Government guidance on P. pluvialis, including symptoms and updates on the demarcated area
Royal Forestry Society guide to P. pluvialis
Dartmoor Tree Surgeons and our sister consultancy company, Advanced Arboriculture, are on hand to answer any queries you may have regarding P. pluvialis, both with respect to specific infected trees and regarding the effects and implications of the disease in general. If you have any concerns about trees you are responsible please don’t hesitate to get in touch for some no obligation expert advice.