In Wisconsin, oak trees are at risk of infection by a deadly disease, oak wilt. It gets transmitted by beetles that carry fungal spores from tree to tree. These spores move inside the tree through openings and infect the vascular system of the tree, the part that moves water and nutrients. Unfortunately, pruning cuts create openings that are perfect for this fungus. If we want to care for trees through pruning, it’s important that the timing is appropriate.
A key rule of thumb is to avoid pruning from April to July in Wisconsin, according to the Wisconsin DNR. In fact, the best time to prune is now – during the dormant season before April. The trees won’t lose the water, nutrients, and food stores in the leaves that would be lost while pruning in the summer. Plus, dormant pruning can take advantage of frozen ground and a clear view of the tree’s structure.
Oak wilt is a continuing challenge for arborists. We have a limited set of options for controlling the disease, much like Dutch Elm Disease, and encourage following best practices, like pruning oaks when dormant, as a simple way to control the oak wilt.
Let’s quickly highlight oak wilt controls that our company provides:
- Don’t prune oaks between April and July.
- Remove diseased oaks immediately to reduce the risk to neighboring trees.
- Severe roots from diseased trees that may be grafted to healthy trees.
- Inject with Alamo to protect the tree’s vessels from infection.
- Plant a diverse variety of species so one disease impacts only part of your tree population.
We love our oak trees and hope you do too! For more information, you can read the USDA Forest Service’s thorough article on oak wilt. In Wisconsin, the Wisconsin DNR offers more local information you might find helpful.
Let’s work together to keep our beautiful oak trees from being distant memories.
Photo by phigits.