Powdery mildew of aspen

The causal agent of this condition is the ascomycete fungus Propolis farinosa. It is primarily known as a pathogen that affects the bark and woody tissues of deciduous trees. Unlike common foliar powdery mildews, this species often manifests through the development of necrotic lesions and distinct fruiting bodies on the tree surface.

The main host for this fungus is the European aspen (Populus tremula). The pathogen typically targets trees that have been compromised by environmental stress, mechanical damage, or secondary pests, entering the host through fissures or injuries in the bark surface where protection is minimal.

Symptoms are characterized by the appearance of small, pale, powdery-looking patches or raised, circular fruiting structures on the bark. As the infection progresses, it causes localized bark death, leading to necrosis. This disruption of the phloem and xylem inhibits nutrient transport, resulting in dieback of branches.

Environmental conditions play a critical role in the development and spread of Propolis farinosa. High humidity and moderate temperatures during the growing season significantly enhance spore production and germination. Poor air circulation in dense plantations further facilitates the rapid dispersal of spores across the site.

The impact of this disease is significant, as it weakens the overall vigor of the trees, making them susceptible to secondary wood-decaying organisms. In forest settings, it contributes to branch failure and reduced quality of wood, which can lead to economic losses if the infection becomes widespread.

Control and prevention strategies focus on maintaining tree health and reducing pathogen inoculum. Proper forest management is essential for long-term control.

• Sanitary pruning of infected branches.
• Removal of dead or heavily diseased trees.
• Ensuring adequate spacing between trees for airflow.
• Applying copper-based fungicides as a preventative measure on valuable specimens.