Cylindrocladium colhounii

Cylindrocladium colhounii is a highly pathogenic fungus belonging to the kingdom Fungi, known for its ability to cause severe damage to various tree and shrub species. Often linked to its teleomorph Calonectria colhounii, this pathogen is recognized globally as a significant threat in nurseries and forest plantations, particularly in tropical and subtropical climates.

This fungus primarily affects species such as Eucalyptus, Acacia, and Camellia, causing distinct leaf spot, shoot blight, and damping-off symptoms. The infection begins with small, discolored spots that rapidly expand, often killing young tissues. In severe cases, the entire plant may collapse due to root rot and collar rot infections, leading to substantial economic losses in commercial production.

The biology of the pathogen relies on its ability to produce abundant conidia, which are disseminated primarily through water splashes, contaminated soil, and infected plant material. The fungus survives in plant debris and soil, maintaining its viability for long periods until conditions become favorable for infection, making it a persistent challenge for land managers.

Development and spread are strongly favored by high humidity and warm temperatures (ranging from +20°C to +28°C). These conditions stimulate spore germination and penetration of the host's epidermal layers. Poor sanitation practices, such as excessive canopy density and inadequate drainage, exacerbate the spread of the pathogen within cultivated plots.

Integrated disease management (IDM) is essential to control Cylindrocladium colhounii, focusing on the following strategies:

• Strict quarantine measures and use of pathogen-free seedlings.
• Timely application of systemic and contact fungicides (e.g., mancozeb, thiophanate-methyl).
• Sanitizing pruning tools and maintaining proper spacing between plants to improve aeration.
• Systematic removal and deep burial of infected plant parts to reduce the initial inoculum level.