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Alder Dieback

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Phytophthora disease of alders (Alder dieback)
Phytophthora disease of alders (Alder dieback), symptoms - Photo by Andrej Kunca; Slovakia National Forest Centre
Scientific Name: 

Phytophthora ×alni (Brasier & S.A. Kirk) Husson, Ioos & Marçais (Husson et al. 2015)


Common Name: 

Alder dieback, alder decline

Native To: 

First identified in Europe (Aguayo et al. 2013)

Date of U.S. Introduction: 

Not introduced

Means of Introduction: 

European introductions occurred through infected nursery stock (Adams et al. 2008)


Infects and kills alder trees (trees of the genus Alnus) (Gibbs et al. 1999)

Current U.S. Distribution: 
Not currently established


USDAAPHISPPQCPHST. Identification Technology Program.

ITP and the APHIS PPQ S&T Beltsville Lab are pleased to announce the release of IDphy: Molecular and Morphological Identification of Phytopthora Based on the Types, ITP’s first pathogen tool. This website offers PPQ and its partners the most complete, valid, and up-to-date resource for identifying the culturable species of Phytophthora. IDphy includes detailed standard operating procedures for all steps involved in culturing, sequencing, and identifying suspect samples, covering both molecular and morphological methods. Some species of Phytophthora are devastating plant pathogens that have a significant impact on agriculture and natural ecosystems.

Distribution / Maps / Survey Status

USDA. APHIS. Cooperative Agricultural Pest Survey. National Agricultural Pest Information System.

Federally Regulated

USDA. APHIS. Plant Protection and Quarantine.

A Federal Order is a legal document issued in response to an emergency when the Administrator of APHIS considers it necessary to take regulatory action to protect agriculture or prevent the entry and establishment into the United States of a pest or disease. Federal Orders are effective immediately and contain the specific regulatory requirements.


University of Georgia. Center for Invasive Species and Ecosystem Health.


Google. YouTube; Swedish University of Agricultural Sciences. Department of Forest Mycology and Plant Pathology.

Selected Resources

The section below contains highly relevant resources for this species, organized by source. Or, to display all related content view all resources for Alder Dieback.

Nature Conservancy. Don't Move Firewood.

USDAAPHISPPQCPHST. Identification Technology Program.

International Government

Forestry Commission (United Kingdom). Forest Research.