Phytophthora pluvialis

Is Phytophthora pluvialis found in Scotland?

The pathogen Phytophthora pluvialis is a fungal-like water mould found in Scotland, infecting western hemlock (Tsuga heterophylla) and Douglas fir (Pseudotsuga menziesii).

How does Phytophthora pluvialis affect trees?

Symptoms of P. pluvialis infection include:

needle cast
shoot dieback
lesions on the stem, branches and roots

More information about symptoms can be found in the Forest Research guide.

Phytophthora pluvialis: Symptoms on western hemlock and Douglas-fir (Forest Research website)

When was Phytophthora pluvialis discovered?

The pathogen was first described in 2013 from Oregon, USA, infecting tanoak (Notholithocarpus densiflorus).

One year later it was discovered to be the causal agent of ‘red needle cast' in radiata pine (Pinus radiata) in New Zealand.

Phytophthora pluvialis was discovered in Scotland in 2021 after extensive surveillance following the first UK detection in Cornwall.

First report of Phytophthora pluvialis in Europe causing resinous cankers on western hemlock (British Society for Plant Pathology website)

Report suspected sightings of Phytophthora pluvialis

Report suspicious symptoms on any tree in Scotland to TreeAlert using the general enquiry webform.

Use TreeAlert (Forest Research website)

The web form asks for:

your contact details
the location of the sighting
clear photographs of the affected tree(s) in context and the symptoms

For more information on what to include in your report, visit the ‘TreeAlert - what to do page’.

What do you need to make your report (Forest Research website)

Once you submit your report, diagnosticians at Forest Research will review it. They may contact you to request additional details.

Any suspected findings of regulated pests or pathogens will be sent to our Tree Health Officers for follow-up.

Restrictions no longer apply in Scotland to manage Phytophthora pluvialis

An initial risk assessment conducted by the UK Plant Health Risk Group in 2021 concluded that Phytophthora pluvialis met the criteria to be treated as a GB quarantine pest, allowing controls and statutory measures to be introduced while further research was undertaken.

Measures taken on a precautionary basis included the introduction of demarcated areas around confirmed outbreak sites and the use of statutory plant health notices.

In 2023, following interim research evidence and publication of a rapid Pest Risk Analysis, demarcated area restrictions on timber movement were lifted but restrictions on movement of plants for planting remained in place.

The Pest Risk Analysis was updated at the end of 2023 with new evidence from the programme of research, concluding that Phytophthora pluvialis does not meet the criteria to be confirmed as a quarantine pest for GB.

As of 4th March 2026, demarcated areas for Phytophthora pluvialis in Scotland are revoked and statutory action will no longer be taken on findings.

Monitoring and surveillance for Phytophthora pluvialis will continue, to ensure that any change in risk is identified early. Please continue to report any suspected findings via Tree Alert.

The UK Plant Health Risk Register entry for Phytophthora pluvialis has links to the Pest Risk Analysis information:

UK Risk Register Details for Phytophthora pluvialis (UK Plant Health Risk Register website)

Plant Health (Phytophthora pluvialis) Demarcated Area Notices

As of 4th March 2024, all demarcated areas for Phytophthora pluvialis in Scotland are removed.

The Plant Health (Phytophthora pluvialis) (Scotland Demarcated Areas Revocation) Notice revokes previous demarcated area notices.

Report suspected Phytophthora pluvialis

To report suspected Phytophthora pluvialis, use TreeAlert.

This online platform allows you to submit symptom observations, including photos and location, helping quicker diagnosis and action.