In early arboriculture, it was common to treat tree wounds with paint or some type of wound dressing. Periodically we get questions about whether or not we should paint our pruning wounds. The short answer is no. The long answer: wound dressing generally does more harm than good. There are a few special circumstances where it could be beneficial however, these situations can usually be avoided with some foresight and planning.
The Bad – Wound Dressing:
- prevents wound wood from forming
- can inhibit compartmentalization
- will not prevent decay or rot
- may be phytotoxic (poisonous to plants) if not specifically labeled for plants
- can provide food for microorganisms
- retains moisture causing increased fungal activity
Think of wound dressing like a band-aid applied to a cut finger. A band-aid will prevent some organisms from entering the wound in the short term, however if left on for years there will be negative effects. Since wound dressing cannot be removed once it is applied, it is best to leave it off. Trees have natural defenses to wounds called compartmentalization. Compartmentalization begins when the tree wound begins to oxidize. Painting the wound seals out air halting oxidization and reducing compartmentalization, allowing for easier spread of decay organisms.
The Not as Bad
Wound dressing can be beneficial in a few special circumstances. These are limited and can often be avoided with a little foresight. An example would be pruning oak trees in an area with oak wilt, a fungal disease carried by a small insect called a nitidulid. Painting wounds can reduce the likelihood of this deadly disease infecting trees. Pruning done when the fungus and insect are inactive eliminates the need for painting wounds.
Since pruning trees is a lot of work, don’t make it worse be adding more unnecessary steps like wound dressing. There is no evidence that it is beneficial to the tree, and there is plenty of evidence that it is harmful. Finally, if in an area with oak wilt or some other highly transmissible disease (currently not a problem in Emporia and Topeka), avoid wounding trees when infectious organisms are active.
For more information check out these sites
Info from Texas about painting wounds in oak wilt prone areas (does not apply to Emporia or Topeka areas at this time)