On a frosty morning in late November (Image), the final cut has been done on the lawn (Image), flowering baskets have been replaced by Christmas decorations (Image), and all that’s left is to pick up leaves. Image
Not so fast! Remember the Oaks! Image
As we look at snow flying, we may not think about our yard or garden. Winter is the perfect time to Prune your Oaks. There are several great reasons but the most important is to reduce the risk to your trees from contracting Oak Wilt. Image
Let’s start with “What is Oak Wilt and why is now a good time to prune Oaks?”
Oak wilt fungus, Bretziella fagacearum, (formerly Ceratocystis fagacearumis) a lethal fungus that can kill a mature Oak in less than a months’ time. It is vectored by the sap beetles, also referred to as Picnic Beetles (Coleoptera: Nitidulidae) which carries the fungus and transmits it while feeding on freshly pruned or damaged Oaks during the summer months. Pruning actively growing Oaks causes them to bleed which can attract picnic beetles that may be carrying the fungus.
If an Oak tree becomes infected, it can transmit the fungus to other nearby oaks that have root grafted to each other. This commonly occurs in a stand of oaks growing together in a forest setting.
For additional information, check out the OSU Factsheet on Oak Wilt at: https://ohioline.osu.edu/factsheet/plpath-tree-02 authored by Pierluigi (Enrico) Bonello with OSU's Department of Plant Pathology.
While all oaks are susceptible to this fungus, those in the red or black oak group including black, pin, northern and southern red, scarlet, shingle and Shumard oak are extremely susceptible and can die within a few weeks of infection. Image
Oaks in the white group that include bur, chinquapin, post, swamp white, and white oak are more tolerant of the disease and can even survive infection for one or more years while displaying declining symptoms. Image
We have passed the time of year where Oaks are actively growing and are now dormant. Typically, the recommendation to not prune is April 15 through October 15. Now that Oak trees are dormant it is a perfect time to prune. In addition, many Arborists tend to have more availability at this time of year. Exceptions would be storm damage (ice or wind) and hazardous conditions of trees that can harm people or property.
A professional arborist will follow procedure to reduce the transmission of oak wilt. The primary protection is dormant pruning between November 1 and April 1.
Pruning can include removing suckers, cleaning out the interior, removing low growing branches, and removing dead wood and branches. Image
By placing a call to your local arborist, you can schedule to have your trees pruned while the Oaks are dormant. This will reduce the risk of Oak Wilt transmission through Picnic Beetle feeding.
So how do I find a certified arborist? The International Society of Arboriculture (ISA) has a locator tool on their website. By putting in your zip code, you can search for local arborists.
https://www.treesaregood.org/findanarborist/findanarborist
In addition, if you have fears about whether your tree is at risk of failing, ISA offers credentials to arborists that have completed the Tree Risk Assessment Qualification (TRAQ). This is not just for oaks but any tree which may present you with concerns.
The ISA Tree Risk Assessment Qualification (ISA TRAQ) is a voluntary qualification program designed to train and assess candidates in a specialized field of arboriculture. When a professional earns the ISA TRAQ credential, they should be recognized by their peers and the public as a tree care professional who has specialized knowledge in tree risk assessment.
Happy Thanksgiving!