Massaria canker

Massaria canker is a serious fungal disease caused by the pathogen Splanchnonema platani. It primarily affects trees of the genus Platanus (plane trees), causing significant dieback of branches and posing a safety risk in urban environments due to the potential for falling limbs.

The fungus attacks the bark and cambium layers of the branches. As the infection progresses, it induces necrotic lesions that disrupt the tree's vascular system. This disruption prevents the transport of water and nutrients, leading to the death of the distal parts of the branch and decay of the underlying wood.

Key symptoms include reddish-brown or grayish discoloration on the bark, often characterized by elongated lesions along the branch. Over time, the bark may crack, and the small, black fruiting bodies of the fungus (pseudothecia) become visible, usually appearing as fine, dotted structures embedded in the bark surface.

The development of the disease is heavily influenced by environmental stress, such as drought, heat waves, and physical injury to the tree. Spores are primarily spread by rain splash and wind, entering the tree through wounds or pruning cuts. The disease can be subtle initially, often remaining unnoticed until major branches begin to die back.

Effective management focuses on the early detection and removal of infected branches through professional pruning. It is essential to sterilize pruning tools between cuts to prevent cross-contamination. Cultural practices, such as maintaining proper hydration and minimizing tree stress, are critical components of a comprehensive preventative strategy.