Lawn care tips

 Black Knot, caused by the fungus Apiosporina morbosa, it 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. 

Amur Cherry - Mayday Tree - Apricot - Mongolian - Cherry Black Cherry - Nanking Cherry - Chokecherry  - Pin Cherry -  Dropmore Cherry - Cultivated Plum - Flowering Almond  -  Wild Plum - Flowering Plum - Prunus Hybrids - Japanese Plum  -  Sand Cherry -  Korean Cherry  -  Sour Cherry 

 The most distinguishing symptom of Black Knot is the characteristic black, tar-like swellings that develop on branches of the infected plant. 

•  The most distinguishing symptom of Black Knot is the 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)