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+1-780-294-9992

Total Landscapes
  • Home
  • Services
  • Contact Us
  • Review
  • Gallery
  • Tips
    • Thatch
    • Black Knot
    • Aeration
    • Mowing
    • Weeds
    • Watering
  • Cancellation Policy

Tree fungus care tips

What is Black Knot?

 Black Knot Tree Fungus, 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. 

Plant Species Affected by Black Knot

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 

How can you recognize Black Knot?

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

What can be done to control Black Knot?

  •  The most distinguishing symptom of Black Knot Tree Fungus 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 are 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)


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