Seiridium canker of cypress

Seiridium canker, caused by the fungus Seiridium neocupressi, is a destructive disease affecting various species within the Cupressaceae family. The fungus acts as a necrotrophic pathogen, invading the vascular cambium and phloem of twigs and branches, which effectively girdles the host and restricts the flow of water and nutrients.

The disease primarily affects ornamental conifers, including genera such as Cupressus, Chamaecyparis, Thuja, and Juniperus. It is a major limiting factor for cypress cultivation in Mediterranean-like climates, where it can cause significant economic losses in nurseries and degradation of ornamental plantings in landscaping.

Typical symptoms of infection include the formation of sunken, elongated, or oval cankers on bark, often accompanied by copious resin exudation. As the pathogen spreads, the distal foliage of the affected branch turns yellow, then orange, and eventually deep brown, signaling the death of that plant part. Dark, pinhead-sized fruiting bodies (pycnidia) often appear on the surface of the cankered bark.

The environmental conditions favoring the disease are high humidity and moderate temperatures, which facilitate the production and dissemination of conidia. Spores are primarily spread by rain splash, wind, and by contaminated pruning equipment. Any form of bark damage, including frost injury or physical wounds from improper pruning, creates an entry point for the fungal spores.

Effective management of Seiridium neocupressi relies on strict sanitary practices and maintaining plant vigor. Once a branch is severely affected, the infection is often irreversible. Key management strategies involve the following practices:

• Pruning out infected branches well below the margin of the canker to remove all fungal biomass.
• Sterilizing all pruning tools with a bleach or alcohol solution between cuts to prevent cross-contamination.
• Improving plant health through irrigation management and fertilization to minimize stress-induced susceptibility.
• Applying preventive copper-based fungicides, especially during periods of wet weather or immediately after pruning operations.