Leucostoma canker

Leucostoma canker is a destructive fungal disease caused by species of the Leucostoma genus, particularly L. cincta and L. persoonii. It is classified as a bark necrosis disease that interferes with the vascular system of trees, leading to dieback and, in severe cases, the death of the tree.

This pathogen primarily targets stone fruit crops, including peach, apricot, cherry, and plum trees. The fungi are opportunistic pathogens that gain entry into the tree through compromised bark surfaces, often initiated by winter injury, sunscald, or improper pruning wounds.

The visual symptoms typically appear as sunken, dark-colored lesions on the bark. As the disease progresses, the necrotic tissue cracks, and the tree often exudes gum (gummosis) as a defense response. Small black pycnidia develop within the dead bark, releasing spores during wet weather, which facilitates the spread to other parts of the orchard.

The development of the disease is highly dependent on environmental factors, with the pathogen thriving in high humidity and areas where trees have suffered from cold stress. Once the fungus establishes itself in the cambium, it spreads rapidly throughout the tree, colonizing healthy tissues and weakening the host plant significantly.

Control of Leucostoma canker relies heavily on sanitation and cultural practices. It is crucial to prune and destroy all infected limbs, sanitize tools to prevent cross-contamination, and protect trees from physical trauma. Maintaining tree vigor through balanced nutrition and preventing sunscald with whitewash are essential components of long-term prevention strategies.