The Town of Falher has identified a noticeable amount of Black Knot infections within the local tree population. To assist in the control of the spread of this disease, the Town of Falher will be accepting tree debris from Black Knot trimming for burning disposal.
We ask that when trimming or pruning infected trees, the debris is disposed of immediately in order to prevent the spread.
Debris can be disposed at the Town of Falher Public Works yard from November 12th – 16th, 2024.
What is Black Knot?
Black Knot, caused by the fungus Apiosporina morbosa, is a very common disease of plants in the genus Prunus. A survey in Alberta revealed a significant and widespread distribution of Black Knot found in commercial, municipal, private and natural plantings. This disease reduces the aesthetic value of affected specimens, as infections spread rapidly; high levels may result in the eventual death of the plant.
How can you recognize Black Knot? The most distinguishing symptom of Black Knot is the characteristic black, tar-like swellings that develop on branches of the infected plant.
Initially, a small, olive-green gall or swelling will develop at a succulent growing point or fruit spur (as a result of spores landing and infection taking place). This swelling will grow until it is mature after 2-3 years. The mature galls are hard, black, 10 to 15 cm (4 to 6 inches) and may be somewhat ruptured. Mature galls will produce and release a vast amount of spores during the bloom period, resulting in a rapid increase in infections. The fungus continues to grow internally and externally, with the branch eventually becoming girdled and dying.
What can be done to control Black Knot?
Removal of sources of inoculum (prevents population build up)
Prune out all knot-bearing branches during late fall, winter or very early spring when plants are dormant and knots are easy to see
Remove infected branches to at least 15-20 cm (6-8 inches) below knot. NOTE: It is preferable to prune an infected branch further back to an appropriate location, such as a healthy collar, rather than leave a stub
As a precaution, cutting blades should be cleaned and disinfected after pruning, if possible, especially if cuts have been made through obviously infected material
For knots on scaffold branches or trunks that can’t be removed, cut away diseased tissue down to good wood and at least 1 cm (1/2 inch) beyond the edge of the knot
Failure to remove branches beyond the internal growth will result in re-growth of the fungus
DISEASED WOOD MUST BE DESTROYED IMMEDIATELY (burned, buried or removed from site). Diseased knots can produce and release spores for up to 4 months after removal. Proper composting can help to accelerate the breakdown of infected materials
Ensure plants are healthy and free from stress(not a guarantee from disease)
Regular monitoring
Ensure adequate canopy ventilation through proper pruning
Chemical control (preventative not curative)
Few choices available
Not usually recommended unless for valuable plantings, such as collections, orchards, arboreta or for severe infestations
Other options
May include use of more resistant selections, ensuring adequate buffer zones between plantings and wild stock, or potential employing biological control products (limited)
