Ash-grey mollisia

Mollisia cinerea, commonly known as the ash-grey mollisia, is an ascomycete fungus frequently found on decaying or weakened wood of deciduous trees. While primarily saprotrophic, it can act as a secondary pathogen, exploiting physiological stresses in the host tree to colonize and break down bark and underlying tissues.

This fungus is found on a wide range of woody plants, including various fruit trees and forest hardwoods like oak, birch, and beech. It particularly targets twigs, branches, and trunks that have suffered from winter injury, sunscald, or improper pruning wounds where the natural defenses of the plant are compromised.

The primary symptom of infection is the emergence of small, disc-shaped apothecia, which appear in clusters. These reproductive structures are characteristically ash-grey or bluish-grey in color and reach a few millimeters in diameter. They are usually found growing on dead bark, often emerging through fissures in the surface of the wood during periods of high humidity.

Environmental factors play a crucial role in the development of the fungus. High moisture levels, such as frequent rainfall or dense canopy conditions, facilitate the release and germination of spores. Once established, the fungus can survive and expand as long as the wood maintains a high level of moisture, making overgrown or poorly maintained orchards highly susceptible.

The economic impact of Mollisia cinerea is associated with the degradation of wood tissue and the weakening of the tree's vascular system. By colonizing the bark, the fungus creates lesions that inhibit normal physiological functions and provides entry points for more aggressive pathogens and wood-boring insects, ultimately reducing the lifespan and productivity of the tree.

Effective control strategies focus on sanitation and preventative care. Gardeners should regularly prune dead or diseased branches and dispose of them away from the orchard to prevent spore dispersal. Properly healing wounds with pruning paint and maintaining optimal tree health through proper fertilization and watering are the best ways to prevent infestation by this fungal pathogen.