Beech Bleeding Canker

**This organism is not known to be present in the United States but poses a threat.  Beech bleeding canker, a disease caused by the fungus-like Phytophthora kernoviae, is not known to be in the United States but may pose a serious risk to US plants should it be introduced. Rhododendrons and European beech are the primary disease hosts, but several other species of tree, shrub, and ornamental plant may be impacted or killed by this disease.

USDA surveys for this disease, and members of the Sentinel Plant Network support early detection efforts by monitoring for symptoms on potential host plants. While symptoms on trunk hosts are easily recognizable, it can be difficult to monitor for beech bleeding canker on many plants because symptoms may appear similar to those caused by less serious diseases and environmental factors.


Following its initial characterization in 2003 during a survey in southwestern England, beech bleeding canker easily secured acknowledgement as a serious plant threat. This disease inflicts severe damage to a range of plants and demonstrates rapid spread of infection following pathogen introduction. Beech bleeding canker’s virulence toward rhododendron outside of the U.S. suggests that similarly significant impacts -- and fatality -- could occur if the disease becomes introduced in the United States. P. kernoviae has been identified in the U.K. as well as Scotland, Ireland, New Zealand, and Chile, causing significant plant damage wherever it becomes introduced.


P. kernoviae may be spread through transportation of infected plants, or contaminated soil or water. According to risk assessments conducted by USDA-APHIS, the most likely pathway for bleeding beech canker into the United States is on infected plants moving in international nursery trade or smuggled in passenger luggage. Between 2005 and 2015, 154 interceptions of P. kernoviae host material were made from passengers traveling between the UK or New Zealand and the United States.

To avoid introducing beech bleeding canker to the U.S., do not import live host plants from infected countries (United Kingdom, Ireland, Chile and New Zealand). If this cannot be avoided, isolate new plants from other plants for 4–5 years. Remember that some plants can be infected and not show symptoms.

To support early detection if it becomes introduced, become familiar with the symptoms of beech bleeding canker and monitor trunk and foliar hosts in botanical collections and natural areas for these symptoms of this disease.


Rhododendron and European beech are recognized as the two main hosts of beech bleeding canker, with rhododendron acting as the main hub from which other plants may become infected. Beech bleeding canker may infect a range of trees, shrubs, and understory plants, manifesting through two separate sets of symptoms.

In trunk hosts, P. kernoviae caused trunk cankers and may ultimately result in fatality. European beech and English oak are susceptible to this form of the disease, also known to be contracted, though less frequently, by tuliptree, sweet chestnut, and horsechestnut.

Foliar (leaf) hosts, including rhododendron species and many other popular ornamental plants, experience a disparate array of typically nonfatal symptoms – specifically leaf necrosis (death of tissue) and shoot blight. Extreme cases may cause death in rhododendron.


Think you've spotted this pest?

If you think you've found this pest in your landscape contact your local extension office to see about sending in a sample.
Find your local extension office here.