Fusarium rot of begonia

Fusarium foetens is a specific fungal pathogen belonging to the Fusarium genus that primarily targets ornamental plant species. It is a highly aggressive fungus responsible for severe stem and root rot, significantly impacting the commercial production of various Begonia cultivars in greenhouse environments worldwide.

The primary hosts of this pathogen are indoor and outdoor begonias, particularly those cultivated in high-density conditions. The infection typically affects the lower parts of the plant, including the roots and the crown, but it can rapidly spread to the stems and leaves under favorable environmental conditions, causing widespread losses in nurseries and greenhouses.

Common symptoms include dark, water-soaked lesions that appear on the leaves and stems. As the infection progresses, these tissues become soft and necrotic, often emitting a distinct foul smell, which is a characteristic diagnostic feature of this species. Wilting is a hallmark of the advanced stage, as the fungal mycelium colonizes the vascular system and blocks water transport within the plant.

Environmental conditions such as high relative humidity, poor air circulation, and overwatering are the main drivers for the development and spread of Fusarium foetens. The fungus can persist in the soil and on contaminated plant debris for extended periods. It is disseminated through irrigation water splashes, contact with infected equipment, and handling during plant maintenance or propagation.

Effective control measures focus on preventive strategies, as curative treatments are often difficult to implement once the symptoms become apparent. This includes utilizing certified disease-free propagation material, maintaining optimal greenhouse hygiene, and managing moisture levels carefully. Should an outbreak occur, prompt roguing and destruction of infected plants are essential to prevent further spread of the pathogen.