Calonectria spathiphylli leaf spot and root rot

Pathogen and disease type. The disease is caused by the pathogenic fungus Calonectria spathiphylli (anamorph: Cylindrocladium spathiphylli). It is a highly destructive soil-borne pathogen that targets the vascular system, inducing severe root and crown rot, which disrupts water uptake and causes the rapid collapse of the host plant.

Susceptible crops. While primarily affecting members of the Spathiphyllum genus, this pathogen has a broad host range in greenhouse environments. It can infect various ornamental foliage plants, leading to significant outbreaks in commercial plant nurseries where propagation happens under humid conditions.

Symptoms and signs. Early symptoms include yellowing and leaf chlorosis, followed by the appearance of dark, necrotic spots with a chlorotic halo. As the infection progresses to the root zone, the plant exhibits signs of permanent wilting. In later stages, the roots become black, soft, and mushy, indicating advanced degradation of the plant tissue.

Conditions for development and spread. The fungus thrives in warm conditions with temperatures ranging from 25°C to 30°C and high soil moisture. It spreads through contaminated irrigation water, infested growing media, agricultural tools, and by the movement of infected plant materials across growing areas.

Damage and control measures. This disease is economically devastating, often resulting in 100% loss of infected crop batches. Management relies on stringent sanitation protocols, including the use of pasteurized soil, quarantine of new arrivals, and the application of systemic fungicides like thiophanate-methyl, although complete removal of infected plants is the most effective containment strategy.

• Sanitize all greenhouse tools regularly.
• Maintain good drainage in pots.
• Ensure proper airflow to reduce humidity.
• Source healthy, certified plant material.