Be Vigilant for Phytophthora Pluvialis
The Royal Forestry Society is urging woodland owners to check for signs of fungus-like pathogen Phytophthora pluvialis as new movement restrictions are announced in England.
Picture: Crown Copyright Forest Research
The Forestry Commission has announced a new demarcated area has been introduced following the identification of the pathogen in a woodland in Shropshire. It will take effect from 16 June. The Notice for Surrey has been revised to correct an error. In England there are also Notices in parts of Cornwall, Cumbria, Devon, Gloucestershire and Herefordshire. Restrictions are also in place in parts of Wales and Scotland.
Phytophthora pluvialis is a fungus-like pathogen known to affect western hemlock, Douglas fir, tanoak and several pine species (in particular radiata pine). It is reported to cause needle cast (where needles turn brown and fall off), shoot dieback, and lesions on the stem, branches, and roots.
Phytophthora pluvialis was first identified in a woodland in Cornwall during routine inspections by the Forestry Commission – the first time it had been recorded anywhere in Europe. Initial demarcation areas came into force in November 2021.
The UK Chief Plant Health Officer has confirmed further findings of the disease in woodlands in the affected areas in England. For symptoms see here. Find details of all demarcation areas in England here. Follow these links for restrictions in place in Wales and in Scotland.
A Forestry Commission webinar gives more details on how Phytophthora pluvialis was first identified and how to spot it. They have also developed this You Tube explanation of how to identify it on western hemlock.
Forestry Commission, Forest Research and the Animal and Plant Health Agency are rapidly conducting further surveillance and diagnostic analysis to understand more about the pathogen and ensure that any required control measures are swiftly undertaken to stop its spread. This includes extensive ground and aerial surveillance as part of a UK-wide survey, and comprehensive research and modelling to explore factors such as climatic and potential species susceptibility and to help inform the management response.
Nicola Spence, the UK Chief Plant Health Officer, said: “We are continuing to take swift and robust action against the findings of Phytophthora pluvialis, as part of our well-established biosecurity protocol used for tree pests and diseases.
“I urge all sectors to support efforts to tackle this pathogen by checking the health of western hemlock and Douglas-fir trees
Any sightings in England, Wales and Scotland should be reported to the Forestry Commission via its Tree Alert online portal. In Northern Ireland sightings should be reported to TreeCheck.
Phytophthora pluvialis, was originally reported in Oregon, USA in 2013 on tanoak and Douglas fir and was subsequently identified as the pathogen responsible for ’red needle cast’ of radiata pine in New Zealand.
Frequently asked questions:
Phytophthora means ‘plant eater’ and is a fungus-like pathogen. There are more than 120 Phytophthora species. Some pose a threat to forest health and can change forest landscapes. For example, Phytophthora ramorum is the causal agent of sudden oak death in California and is a major killer of larch in the UK.
It is a fungus-like pathogen which was first isolated in 2008 but had previously been recovered from tanoak (Notholithocarpus densiflorus) and Douglas fir (Pseudotsuga menziesii) trees in Oregon, USA. It has also been identified on radiata pine in New Zealand.
Phytophthora pluvialis was described as a new species in 2013. It is known to affect a variety of trees including western hemlock, tanoak, pine (Pinus radiata, Pinus patula and Pinus strobus) and Douglas fir.
Douglas fir is considered one of the most important tree species in the timber trade worldwide. It is a dominant tree species in the U.S. Pacific Northwest, with remarkable ecological and economic significance. It is widely cultivated in Central Europe and New Zealand
In the UK it is classified as a Principal tree species widely used in forestry and is being planted more widely as we look to increase home grown timber.
Douglas fir produces a strong timber used in boats and construction and grows particularly well in Western areas with high rainfall.
Western hemlock is also an important timber tree and widely planted in the UK and used in general construction for roof decking and plywood. the UK is the first place it has been reported on western hemlock.
Radiata pine, also widely used in construction, is also among species being planted for its potential to help our woodlands adapt to climate change.
It causes die back on shoots and heavy needle cast which in turn impacts on the growth of trees. We are waiting for more information from experts on any impact on timber integrity.
It is early days in the investigations. We don’t yet know and do not wish to speculate.
Forestry Commission, Forest Research and the Animal and Plant Health Agency are rapidly conducting further surveillance and diagnostic analysis to understand more about the pathogen and we will be passing that information on to woodland owners when it becomes available.
The movement of Phytophthora species has been well documented for some species and modelled using molecular markers for others. Movement of spores can occur through soil, streams, wind and rain, as well as by humans and animals
Experts are working on how Phytophthora pluvialis spreads and we are waiting to learn more.
There is some genetic evidence from two clusters of outbreaks in radiata pine in New Zealand that it may have been introduced to New Zealand from the USA.
This pathogen has also been isolated from Douglas-fir seedlings that were grown in close proximity to diseased radiata pine in New Zealand.
It has a been identified in environmental rain traps, streams and occasionally from tanoak twig and stem cankers.
We cannot say that with any certainty.
We know Phytophthora pluvialis flourishes in damp humid conditions. These conditions are predicted to become more frequent under some climate change scenarios developed for the UK.
No, Ash dieback is caused by a fungus named Hymenoscyphus fraxineus – also known as known as ‘chalara’ ash dieback – which is of eastern Asian origin.
However, potential negative impacts on other key forestry species is a concern for those looking to plan and restock our future woodland and forests.
Be vigilant and check your woodland for symptoms. In both radiata pine and Douglas-fir, Phytophthora pluvialis infection is characterized by the production of olive-coloured lesions and black resinous bands on needles followed by accelerated aging (senescence) and casting.
A Forestry Commission webinar gives more details on how Phytophthora pluvialis was first identified and how to spot it. They have also developed this You Tube explanation of how to identify it on western hemlock.
An article ‘ Phytophthora pluvialis – a new threat to forestry’ by Ana Perez-Sirerra, Ben Jones, Mick Biddle and Joan Webber also appeared in the April QJF. Members can access it online.
A full guide to symptoms can be found here.
Report any suspected cases to Tree Alert here.
In Northern Ireland use TreeCheck here.
