Pruning, Sanitation, and Disease Management
The Kentucky gardener was proud of the basket of apples that she had raised. So the apples were put away for a time, but when the gardener got back to them, she discovered that most of them were rotten. Then she remembered having left in the basket one apple with a small decayed spot on it. Were there lessons to be learned by our intrepid Kentucky gardener? Like, can one rotten apple spoil the whole barrel? Like, using good sanitation can prevent disease? Can we apply this lesson of sanitation to how we manage diseases of plants in the landscape?
Sanitation. What does that mean? Sanitary measures are those efforts at cleanliness that affect health by removal of dirt and germs, or microbes that promote disease. So sanitation, which is the practical application of these cleanliness measures, is very important for maintaining plant health in the landscape. When using integrated pest management in the landscape, sanitation is one of the most important strategies for plant disease management. How do we apply sanitation to our landscape plants?
For a start, remove dead plants and dead plant parts. Every time pruning is done on landscape trees and shrubs, look for diseased branches and remove them and destroy them so the germs or microbes don’t hang around to infect the plants. Remove plant debris - yes, those fallen leaves may harbor microbes that can cause disease. A good example is the scab disease of crabapple which can be reduced greatly if only a little sanitation is used - that is, rake up and destroy the fallen leaves.
Pruning is a powerful sanitary measure. A word of caution is needed, here, however. Pruning needs to be done properly. It is obvious that tree topping should be avoided at all costs. Gardeners need to learn the techniques of natural target pruning, that is one should neither leave a branch stub, nor should one use a flush cut that cuts into the branch collar. By leaving a stub, a food base is left for wood decay fungi and it gives them a head start into the heart of the tree. Look for the branch collar, that slightly swollen region where a branch meets a limb, or a limb meets the trunk. If a limb is cut too close to the trunk and part of the branch collar is injured, then the tree can no longer efficiently defend itself against heart rot fungi.
After all, like our intrepid gardener learned, we don’t want that one rotten branch to spoil the whole tree. And we don’t want that one spotted leaf or cankered branch to spoil the whole tree or shrub. Use sanitation, it works.