Alder phytophthora

The pathogen responsible for this condition is the oomycete Phytophthora polonica, a fungus-like organism that targets the root systems and the lower trunks of woody plants. It acts as a severe vascular pathogen, disrupting the tree's ability to transport water and essential nutrients from the roots to the canopy.

The primary host for this specific pathogen is the black alder (Alnus glutinosa). Given that this tree species thrives in riparian zones and wetlands, the presence of the pathogen poses a significant threat to riverbank stability and the overall biodiversity of the forest stand.

Symptoms of an infection include yellowing foliage, reduced leaf size, and a thinning crown. A diagnostic feature is the appearance of bark necrosis at the base of the stem. Under the bark, you can often observe dark, bleeding lesions that indicate the active progress of the pathogen within the phloem.

Environmental conditions play a crucial role in the lifecycle of Phytophthora polonica. High moisture levels, particularly saturated soils and flowing water, facilitate the movement of motile zoospores. These spores can easily spread from tree to tree, especially following flood events which distribute the pathogen over larger distances.

• Monitor forest health near waterways.
• Avoid movement of contaminated soil.
• Ensure strict hygiene for forestry tools.
• Identify and remove severely affected trees.
• Promote biodiversity to improve stand resilience.

Current management strategies rely heavily on preventative measures. Because chemical treatment in forest environments is impractical and often ineffective, success lies in preventing the introduction of the pathogen into new areas and maintaining the overall vigor of the alder population.