Botryodiplodia canker

Botryodiplodia canker is a serious fungal disease caused by the pathogen Botryodiplodia hydrodermia. It is classified as a bark and cambium necrosis disease, which disrupts the transport of nutrients within the tree. Over time, the infection can girdle stems or branches, leading to the rapid wilting and dieback of the affected parts.

The disease primarily affects various species of Elm (Ulmus), particularly those under environmental stress or those suffering from mechanical damage. The pathogen exploits weak points in the bark to enter the tree's vascular system. In landscape settings, high-density elm plantings can be particularly vulnerable to rapid spread if sanitary protocols are not strictly followed.

Symptoms of the infection include sunken areas of bark, discoloration, and eventual cracking of the bark surface. As the infection progresses, the inner tissues become necrotic. A distinctive visual identifier is the eruption of small, black fruiting bodies (pycnidia) through the bark surface, indicating that the fungus is preparing to release spores to infect neighboring trees.

The development and spread of Botryodiplodia hydrodermia are heavily dependent on environmental conditions, with high humidity and warm temperatures favoring spore germination and growth. The fungus overwinters in infected bark and woody debris. Dissemination occurs primarily via splashing rain, wind currents, and insect movement, which facilitates the transmission of the disease throughout a forest or nursery.

Management of the disease centers on preventative measures and early detection. It is crucial to practice good sanitation, including the removal and destruction of infected limbs. Protecting trees from drought and mechanical injuries reduces susceptibility. In areas where the disease is prevalent, regular monitoring and the use of fungicides during the growing season can help mitigate the impact of the infection on tree health.