Resin cancer of conifers

Resin cancer, caused by the fungal pathogen Zythia resinae, is a significant disease affecting various coniferous species. This fungus functions as a necrotrophic pathogen, invading the vascular system and bark, which disrupts the transport of nutrients and water within the tree.

Typical hosts for this infection include species within the Pinaceae family, particularly pines and spruces. The fungus primarily targets younger trees or those that have been physically damaged by pruning, frost cracking, or insect activity, providing an entry point for the mycelium.

Clinical signs of infection are characterized by excessive resin flow (resinosis) at the site of the lesion. As the infection progresses, small, distinct, brightly colored pycnidia appear on the affected bark. Over time, the localized bark tissue dies and collapses, resulting in perennial cankers that can girdle the stem or branches.

The spread of Zythia resinae is heavily dependent on moisture and humidity levels. Rain splashes and wind currents serve as primary dispersal mechanisms for the fungal spores. Once a tree is stressed by environmental factors, it becomes highly susceptible to colonization, often leading to rapid expansion of the disease within a stand.

Management of the disease focuses on strict phytosanitary measures, including the excision and disposal of infected branches and stems to reduce inoculum pressure. Maintaining vigorous tree growth through proper irrigation and fertilization is crucial for natural resistance. Chemical control using copper-based fungicides can be effective if applied early to wounded surfaces.