STONY PLAIN, AB: The Town of Stony Plain is taking a proactive step towards protecting our cherished trees by launching an insightful Black Knot Awareness Campaign. This fungal disease, caused by Apiosporina morbosa, manifests as greenish brown to black swellings on the stems of trees, most commonly cherry or fruit varieties.

The fungus primarily spreads its spores during warm, wet weather, utilizing various carriers such as splashing water, wind, birds, and insects. Black Knot disease has become increasingly common and poses a significant threat to the local tree population.

“Early detection and sterile pruning are fundamental in effectively managing Black Knot disease,” says Stony Plain Mayor William Choy. “The disease deforms branches, stunts growth, and can ultimately lead to the demise of heavily infected trees. Our mission is to curb its impact and preserve our town’s natural beauty.”

The distinctive appearance of Black Knot disease begins with a small olive-green growth at a succulent growing point or a short twig with fruit buds. Over the course of 2 to 3 years, the swelling matures into a hard, black growth of 10 to 15 cm, often somewhat ruptured. These growths release an extensive amount of spores during the bloom period, accelerating the spread of infections and furthering the fungus’s growth both internally and externally, eventually leading to the tree branch’s demise.

To combat this challenge, the Town of Stony Plain has designed a strategic Black Knot pruning rotation divided into 5 zones: “Crews will commence with zone 1 in Fall 2023, ensuring a systematic and thorough approach to tree care,” says Parks & Leisure Supervisor, Darcy Carter. “Pruning takes place between late fall to early spring when the tree and spores are dormant, and the knots are more visible. The Town is exclusively authorized to prune infected trees on public property, including Open Spaces and Boulevard Trees, and utilize sterilized tools and equipment to prevent disease spread.”

Residents are encouraged to contribute to the efforts by regularly monitoring their trees for Black Knot symptoms and adhering to the guidelines for pruning infected branches. For detailed information on identifying Black Knot signs, the ongoing pruning zones, and resources for tree pruning companies, please visit our Plants and Trees webpage.