Leucostoma canker

Leucostoma cincta is a fungal plant pathogen belonging to the Kingdom Fungi and the Phylum Ascomycota. It is recognized as a major cause of perennial canker, a destructive disease that affects stone fruit trees worldwide. The pathogen is opportunistic, often infecting tissues that have been compromised by environmental stress or physical injuries.

The fungus primarily attacks species within the Prunus genus, including peach, apricot, plum, cherry, and almond trees. The disease is characterized by the formation of sunken, necrotic cankers on the bark, accompanied by heavy gummosis. Over time, these cankers girdle branches or the main trunk, leading to the dieback of limbs and, eventually, the entire tree.

The life cycle of Leucostoma cincta involves overwintering as mycelium within the wood and bark of previously infected trees. During the spring and periods of high rainfall, the fungus produces spores (conidia and ascospores) that are dispersed by wind and splashing rain. Infection occurs when these spores enter the tree through pruning wounds, winter injury, or insect feeding sites.

The prevalence of this pathogen is highly dependent on environmental conditions, particularly moisture levels and temperature fluctuations. Trees that suffer from frost damage or lack proper horticultural care are significantly more susceptible to infection. The pathogen exploits the weakened defense mechanisms of the tree to penetrate deeper into the vascular tissue.

Effective management requires a multi-faceted approach centered on cultural practices. Growers should prune trees during dry, dormant periods to minimize exposure to spores. All cankered wood must be pruned and burned immediately. Protecting the trunk from sunscald with white latex paint, controlling wood-boring insects, and ensuring optimal nutrient management are essential strategies to prevent the establishment of the fungus in the orchard.