Cucurbit anthracnose

Colletotrichum orbiculare is a dangerous plant pathogenic fungus belonging to the genus Colletotrichum. It serves as the primary causal agent of anthracnose in cucurbits, including cucumbers, melons, watermelons, and squash. The fungal mycelium develops within plant tissues, leading to necrotic spots and premature death of vegetative parts.

The disease is characterized by circular or angular brown lesions appearing on leaves, stems, and fruits. In high humidity, these infected areas develop a pinkish mass of spores (conidia). On fruit, the fungus often creates deep, sunken craters or lesions, rendering the produce unsuitable for storage or fresh market sale.

The life cycle of the fungus includes primary and secondary infection phases. The pathogen survives in soil debris and is often seed-borne. During the growing season, spores are dispersed by splashing water, rain, wind, or farm equipment. Fungal development is favored by temperatures between 22°C and 27°C and relative humidity levels exceeding 90%.

The economic impact of the disease is severe, with the potential to destroy 50–80% of a crop during extended wet weather periods. Infected plants show reduced vigor, while deformed and rotting fruits result in significant post-harvest losses. Severe stem infection can result in the complete collapse of the plant canopy.

Management strategies require an integrated approach including cultural and chemical controls. Implementing a crop rotation cycle that excludes cucurbits for at least 3-4 years, using disease-free seeds, and thorough post-harvest residue removal are essential. Chemical control is achieved through the application of fungicides, such as strobilurins and triazoles, when favorable weather conditions for disease spread occur.

• Use of resistant varieties and hybrids
• Optimal plant spacing to encourage airflow
• Proper greenhouse ventilation
• Preventive fungicide application