Alder leaf blister

Alder leaf blister is a fungal disease caused by the ascomycete fungus Taphrina tosquinetii. This pathogen is an obligate parasite that specifically infects various species of the Alnus genus, resulting in distinctive morphological changes in the host's foliage.

The disease primarily impacts common alder (Alnus glutinosa) and grey alder. It is frequently observed in nurseries, young plantations, and forests situated in damp, humid environments where the pathogen can easily complete its infection cycle and thrive over multiple growing seasons.

The symptoms of the infection become visible in early spring as new leaves unfold. Affected leaves display severe curling, puckering, and thickened, distorted blades. These areas often shift in color, developing reddish, brownish, or yellowish patches, which clearly indicate the disruption of cellular functions.

The development and dissemination of the fungus are strictly dependent on environmental conditions. Excessive rainfall and high relative humidity during the spring growth phase facilitate spore dispersal and infection. The fungus overwinters in tree bark crevices and bud scales, waiting for favorable moisture levels to initiate the cycle anew.

The economic impact and damage caused by this pathogen involve premature leaf drop and overall tree physiological stress. Continued infection over several years results in stunted shoot growth, weakened vitality, and diminished aesthetic value in landscape settings, sometimes leading to the decline of young, vulnerable saplings.

• Regular pruning and removal of infected branches and litter.
• Application of copper-based fungicides during the dormant season.
• Ensuring proper site drainage to reduce local humidity.
• Promoting tree vigor through site-specific silvicultural practices.