Fusicoccum canker, also known as Godronia canker, is one of the most important fungal diseases affecting blueberry plants and is considered the second most common canker disease after mummy berry–related stem blights. Caused by the fungus Fusicoccum putrefaciens, this disease is particularly widespread in cooler blueberry-growing regions such as the northern United States and Canada. In recent years, it has become one of the most frequently reported diseases of highbush blueberry in the Lower Mainland of British Columbia, where climate conditions favor its development.
The disease primarily attacks young to middle-aged stems, typically those that are one to three years old. Early in spring, small, reddish-brown, water-soaked lesions appear, often at leaf scars or buds where the fungus can easily enter the plant. As the season progresses, these lesions enlarge and develop gray centers with dark, sometimes target-like margins, forming visible cankers. One of the most recognizable symptoms occurs in summer and is known as “flagging,” where infected branches suddenly wilt, turn reddish-chocolate brown, and die while neighboring shoots remain healthy.
As cankers expand, they may girdle the stem, blocking water and nutrient movement. This leads to dieback of the affected portion of the plant, reduced fruit production, and overall weakening of the bush. In severe cases, repeated infections can kill entire plants. Within mature cankers, small, dark, pimple-like structures called pycnidia often appear. These structures produce large numbers of conidia, or asexual spores, which are responsible for spreading the disease.
The disease cycle is driven almost entirely by the asexual stage of the fungus, Fusicoccum putrefaciens. Although the pathogen has a sexual stage known as Godronia cassandrae, research indicates that it plays little to no role in disease spread. The fungus survives the winter in old cankers and those formed during the previous growing season. During wet weather, especially when temperatures range from 8°C to 22°C—with optimal activity around 16°C—spores are released and spread by rain splash to new infection sites.
If left unmanaged, Fusicoccum canker can significantly reduce blueberry yields and plant longevity, making early detection and proper management essential for maintaining healthy blueberry fields.Fusicoccum (Godronia) Canker of Blueberry: Symptoms, Spread, and Impact
