Pitch canker

Pitch canker is a devastating disease caused by the fungus Fusarium circinatum. This pathogen is globally recognized as a major threat to forestry, particularly affecting a wide range of pine species and some other conifers. It is classified as a quarantine pest in many jurisdictions due to its potential to cause severe economic and ecological damage to natural forests and commercial plantations.

The disease primarily targets species such as radiata pine, maritime pine, and many others. It affects trees at all growth stages, from seedlings in nurseries to mature trees in commercial stands. In nursery conditions, the disease can cause significant mortality rates, often wiping out entire batches of seedlings if left unmanaged, which complicates efforts to supply healthy reforestation materials.

Typical symptoms include resin-soaked wood, discolored foliage, and the development of cankers (lesions) on stems, branches, and the main trunk. Infected seedlings often exhibit damping-off, while older trees show tip dieback and flagging. A diagnostic feature is the presence of deep, resinous lesions that penetrate into the xylem, causing structural weakness in the tree and eventually leading to its death.

Environmental factors play a crucial role in the development and spread of Fusarium circinatum. High humidity, mild temperatures, and frequent rainfall create optimal conditions for the fungus to reproduce and spread via wind-borne or rain-splashed spores. Additionally, mechanical damage caused by insects, pruning, or heavy weather events provides entry points for the pathogen to infect the host tissue.

Management and prevention focus heavily on phytosanitary measures, as curative treatments for established infections in forest settings are generally impractical. In nursery operations, strict hygiene, the use of pathogen-free seeds, and the removal of infected plants are essential. Integrated pest management, including the use of resistant genotypes and regular monitoring for symptoms, remains the primary approach to mitigating the impact of this serious forest pathogen.