In early arboriculture, it was common to treat tree wounds with paint or a 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, but if left on for years, it can have negative effects. Since wound dressings cannot be removed once applied, it is best to leave them off. Trees have a natural defense against wounds called compartmentalization. Compartmentalization begins when the tree wound begins to oxidize. Painting the wound seals out air, halting oxidation 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.
Conclusion
Since pruning trees is a lot of work, don’t make it worse by adding more unnecessary steps like wound dressing. There is no evidence that it benefits the tree, and plenty that it harms it. 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 the Morton Arboretum
Info from the Missouri Botanical Garden about painting wounds in oak wilt-prone areas (does not apply to the Emporia or Topeka areas at this time, but that could change in the future)
