Phytophthora plurivora

Phytophthora plurivora is a destructive soil-borne oomycete pathogen that causes significant economic damage to forests and ornamental plant nurseries. As a member of the Peronosporales order, it is recognized for its broad host range and high adaptability in diverse environmental settings, making it a persistent threat to woody plant species.

This pathogen primarily targets trees and shrubs, inducing root rot, stem cankers, and collar rot. Common hosts include species of Fagus (beech), Quercus (oak), and Rhododendron. The disease often manifests as progressive dieback of the crown, leaf chlorosis, and eventually, the sudden or slow decline and mortality of the affected host plant.

The biological cycle of Phytophthora plurivora relies on the production of motile zoospores that migrate through saturated soil or surface water to locate host roots. Once contact is made, the pathogen colonizes the root tissues, destroying vascular integrity. It survives adverse periods by forming resistant oospores and chlamydospores, allowing it to persist in the soil for several years.

Environmental conditions favoring the development and spread of the pathogen include poor soil drainage, waterlogging, and moderate temperatures. Human activities are the primary vectors for long-distance dissemination, specifically through the movement of contaminated nursery stock, infected root balls, and infested soil transported on agricultural machinery or footwear.

Management strategies focus on a multi-pronged approach: prevention is paramount, starting with the use of certified pathogen-free planting stock and strict nursery hygiene. Chemical control involves the application of systemic fungicides, such as phosphonates, during early stages of infection. Site management, including improving soil aeration and moisture regulation, is essential to reduce the risk of further outbreaks.