Gum canker of pistachio

Gum canker, caused by the fungus Cytospora terebinthi, is a severe fungal disease that primarily affects the bark and vascular tissues of trees. As a parasitic pathogen, it thrives in stressed trees, exploiting wounds and weak points to establish a successful infection colony within the host plant.

The primary host for this pathogen is the Pistachio tree (Pistacia vera). The infection interferes with the tree's vascular system, hindering the transport of water and nutrients, which eventually leads to the wilting and eventual dieback of branches and limbs.

Typical symptoms include the development of depressed cankers on the branches and trunk, which are frequently accompanied by significant gummosis (oozing of sap). The affected bark becomes discolored and brittle, and during humid conditions, small fruiting bodies (pycnidia) of the fungus emerge on the surface to release spores.

The development and spread of the disease are heavily influenced by environmental stressors such as extreme temperatures, drought, or poor soil nutrition. Spores are disseminated by splashing rain, wind, or agricultural tools used in pruning, facilitating the rapid spread of the fungus across the orchard during moist seasons.

Integrated management is essential for controlling gum canker. This includes regular sanitation, such as pruning infected branches well below the visible symptoms, painting pruning wounds with protective fungicides or sealants, and maintaining the tree's health through optimal irrigation and fertilization. Preventing mechanical injury remains the most effective form of long-term prophylaxis.