Otthia canker

Otthia canker is a fungal disease caused by species within the genus Otthia, primarily affecting various woody plants and shrubs. These ascomycete fungi are known to colonize the bark and underlying tissues, eventually leading to localized necrosis and vascular obstruction within the host plant.

The disease targets a range of hosts, including common orchard fruit trees and various ornamental shrubs. The infection typically begins when fungal spores enter through wounds, pruning cuts, or frost-damaged areas of the bark, establishing a foothold in the susceptible host tissue.

Initial symptoms are characterized by small, discolored lesions on the bark that expand into sunken cankers over time. As the fungus develops, small black fruiting bodies appear on the surface of the infected bark, often becoming visible as the disease progresses to its reproductive stage.

Environmental conditions that favor the spread of Otthia include high humidity, prolonged dampness, and poor air circulation within the canopy. These conditions allow spores to germinate and spread rapidly via splashing rain, wind, or contaminated pruning tools, which can facilitate the transmission of the pathogen throughout a nursery or orchard.

The economic impact of this disease is significant, as it leads to twig dieback, reduced vigor, and the potential loss of entire branches. Effective management involves a combination of cultural practices, such as removing and destroying symptomatic branches, keeping tools sanitized, and applying protective fungicides during periods of high risk. Maintaining plant health through proper fertilization and stress reduction is also crucial for preventing secondary infections.