Water lily anthracnose

Pathogen and disease type. The causative agent of water lily anthracnose is the fungus Colletotrichum nupharicola. It is a pathogenic fungus belonging to the Ascomycota phylum, known for infecting the foliage of various aquatic plant species. This disease is classified as an anthracnose, characterized by localized tissue death and the presence of fungal fruiting bodies called acervuli on the necrotic lesions.

Host range. The fungus specifically targets members of the Nymphaeaceae family, primarily species within the Nuphar and Nymphaea genera. It is a significant problem in commercial aquatic plant nurseries and private ornamental ponds, where environmental conditions often remain stable enough to facilitate the survival and spread of the pathogen throughout the growing season.

Symptoms and signs. Symptoms manifest as circular or irregular brown to dark lesions on the leaf blades. As the infection progresses, these spots expand, often causing the leaves to become brittle and eventually rot. Under high humidity, the characteristic spore-bearing masses of the fungus appear as tiny clusters or pustules within the center of the necrotic tissue.

Environmental conditions. Colletotrichum nupharicola thrives in warm, humid environments with stagnant water. Optimal temperatures for the infection are generally between 20°C and 25°C. Crowded planting conditions prevent adequate water circulation, increasing local humidity and creating an environment where spores can easily germinate and infect new leaves after physical damage.

Harmfulness and protection. The disease significantly reduces the ornamental value of water lilies and can weaken the entire plant if left untreated. Control measures focus on strict sanitation, including the prompt removal of infected leaves from the pond. Maintaining good water quality, providing adequate space between plants, and monitoring for insect pests that cause leaf damage are essential components of an effective integrated pest management program.