Catkin cup fungus

Mollisia amenticola is a fungal pathogen classified within the order Helotiales that specifically targets the reproductive structures of alder trees. As a parasitic organism, it focuses its life cycle on the catkins, leading to significant physiological stress during the tree's flowering phase. It is a well-documented subject in forest pathology, particularly concerning the health of Alnus species.

The primary hosts for this pathogen are various species of alder (Alnus spp.). The fungus exclusively infects the male catkins, hindering the normal pollination process and seed development. By concentrating its activity on these reproductive organs, the fungus can severely impact the natural regeneration and seed yield of affected tree stands.

Symptoms of the infection involve the appearance of small, disc-shaped apothecia on the surface of the catkins. These fruiting bodies are typically white or greyish and signal that the fungus has colonized the tissue. Infected catkins become necrotic, turn brown, lose their structural integrity, and eventually drop from the branches prematurely before pollination is complete.

The development and spread of Mollisia amenticola are highly dependent on environmental conditions. High humidity levels, prolonged rainfall, and cool temperatures during the early spring create ideal conditions for spore germination and colonization. The pathogen survives the winter in fallen plant debris, providing an inoculum source for the following season's infections.

• Remove and destroy fallen infected catkins to reduce the inoculum level.
• Maintain proper tree spacing to ensure good air circulation within the canopy.
• Apply preventative fungicides in early spring before significant spore discharge occurs.
• Monitor tree stands annually to assess the intensity of the infection.

Preventative management is the most effective approach in controlling the spread of the fungus. Maintaining good forest hygiene and optimizing microclimatic conditions are crucial. In severe cases, particularly in nurseries, chemical treatments must be timed precisely with the developmental stages of the pathogen to ensure the protection of the catkins during their most vulnerable period.