What is ‘Black Knot’?Check this out! One of our technicians brought in a branch this week with a strange bulbous-looking fungus growing on it; have you ever seen anything like it? Our technician explained that it is called “Black Knot,” a disease that commonly affects Cherry and Plum trees. It is caused by a fungus that will infect the wood on twigs, branches, and stems. At first, the fungal spores will create light brown swellings; these swellings are not very noticeable, and will eventually turn green. In the last phase, the green will progressively get darker until it is black. It will harden and become rough, becoming a ‘black knot’ around the branch or stem. The disease doesn’t stop there! It will continue to grow and can begin to girdle the branches it rests upon. When girdling happens, the affected twigs are cut off from water and will eventually die.
Taking ActionDid you realize how serious a little fungus like this could be? While the fungus might not look too serious, it can girdle branches, cut them off from nutrients, and kill them. So, what action can be taken to prevent Black Knot from taking over and girdling affected tree branches? This type of fungus will spread to other susceptible trees if given the chance. There are only a few ways to get control of this kind of disease:
- One way is to very carefully prune the affected branch or stem; cuts need to be made around 6-8 inches below the infected area. Not only that, but any equipment used to prune around the Black Knot will have to be sterilized after each cut so as not to spread the infection further.
- As a last resort, burning the affected branches or removing the entire tree can be used to control Black Knot.