Anthracnose of water lilies

Colletotrichum nymphaeae is a significant fungal pathogen responsible for anthracnose disease in a variety of plant species. While identified with water lilies, this fungus has a broad host range, causing substantial economic losses in berry crops like strawberries. The pathogen is known for its ability to persist in the environment and adapt to various climatic conditions, making it a persistent threat to horticulture.

The host range is diverse, primarily affecting species within the Nymphaeaceae family, but also causing severe infections in Rosaceae, particularly strawberries. The fungus attacks aerial plant parts, including leaves, stems, flowers, and fruits. Infections on strawberries often manifest as rapid wilting of blossoms and necrotic lesions on ripening fruit, significantly reducing overall harvest yield.

Symptoms typically present as localized, sunken necrotic spots that vary in color from brown to black. As the infection progresses, these spots often develop pinkish or orange slimy masses, which are characteristic of the pathogen's sporulation (acervuli). In aquatic plants, the disease can lead to extensive leaf necrosis, weakening the plant's ability to photosynthesize and eventually killing the aquatic structure.

The development and spread of Colletotrichum nymphaeae are strongly favored by high humidity, frequent rainfall, and warm temperatures. Spores are easily disseminated by water splashes, irrigation systems, and human activity within the planting area. The presence of water film on the foliage is a critical requirement for successful spore germination and host colonization.

Management of this disease requires an integrated approach. Sanitation is paramount: infected plant material must be removed and destroyed immediately to reduce inoculum pressure. Fungicide applications, focusing on protective and systemic products, are effective if applied early in the disease cycle. Furthermore, improving air circulation and managing water quality can significantly reduce the risk of successful infection.