Phytophthora alder decline: disease symptoms, causal agent and its distribution in the Czech Republic

摘要

Phytophthora decline of riparian alder populations has recently become an important problem in many European countries, including the Czech Republic. The causal agent, Phytophthora alni, has spread quickly in the Czech Republic. Hundreds of kilometres of riparian alder stands, especially in the western part of the country, have been severely affected to date. Diseased trees show symptoms characteristic of Phytophthora root and collar rot; these include small, sparse and yellowing foliage, crown dieback, presence of exudates on the bark and necroses of collar and root tissues. Infected trees usually die within a few years, or they become irreversibly damaged, and their function in bank reinforcement declines. The ecological and mechanical functioning of severely affected alder stands may be seriously disrupted.