On the twigs, you’ll see a soft olive green growth and it will change to hard black knots in the fall. Large clumps of bark swell on the ends of branches and twigs of the tree. This disease mostly attacks fruit and branches. This disease is life threatening if not treated.

Black Knot Close Up

What Will Happen To My Landscape?

Black knot only affects certain trees, but once it takes hold, it can claim an entire tree within a few years.

What Can I Do About Black Knot?

Prune four (4) inches away from the signs of infection towards the trunk of the tree to help to control the disease from spreading. Disinfect your pruning tool in a bleach solution of one part household bleach to four parts water after each cut. Make sure to destroy the infected trimmings. In some severe cases of black knot, it may be better to remove the entire tree from the landscape than to keep it and put the other trees at risk. A combination of cultural and chemical control is often required. Use a fungicide each spring to help combat the fungus that spreads this disease. Most local hardware stores carry fungicides that will help to control and prevent black knot. Because these sprays can cause injury to some plants, read the label thoroughly before using and apply according to the directions. Depending on the severity of the damage, more than one fungicide application may be required for complete control. Combating black knot can be a timely and unpleasant weekend task.

How Can Natural Way Help?

Prevention is the key in controlling black knot. Here at Natural Way we have certified professionals who can give you advice on pruning and are used to preventing and controlling diseases like black knot. Our 6 Point Protection Program will provide several critically timed sprays that will prevent black knot, extend the life of your trees and minimize overall damage.

Black Knot on Trees

Photo of Black Knot disease symtoms on tree branches – Credit: Joseph O’Brien, USDA Forest Service,