Do you have chokecherry or ornamental cherry trees in your yard? Have you noticed that they have any black clumps on them that are stuck to the branches? These clumps are a tree disease known as Black Knot and there have been quite a few sightings of it around Saskatoon.
What is black knot?
Black knot is a fungus that affects native chokecherry and pin cherry in Saskatchewan, but can spread into ornamental cherries. Black knot is easily noticable due to the large black growths developing on stems and branches. These will usually begin as greenish brown swellings on one side of the branch and develop into large black malformations.
What can I do if I have black knot on my tree?
If you have black knot on your tree, the only effective control is pruning. Pruning of infected branches at least 10-15cm below the knots should remove the infection on that particular branch. Multiple prunings to
remove more than one infection requires sterilizing your pruning shears before and after every cut to prevent spreading of the fungus. This can easily be done using a 10% bleach solution sprayed onto the cutting edge of your pruning shears.