OK to prune OAKS. Now’s the time to schedule!

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As we approach winter, and the Christmas season, here’s another thing to add to your list; Pruning your Oaks this Winter.







There are several great reasons but the most important is to reduce the risk to your trees from contracting Oak Wilt.


Let’s start with “What is Oak Wilt and why is now a good time to prune Oaks?”


Oak wilt is a fungus, Bretziella fagacearum, (formerly Ceratocystis fagacearumis). 





It causes the vascular tissue to clog.






This lethal fungus that can kill a mature Oak in less than a months’ time.


wilt leaves






It is vectored by the sap beetles, also referred to as Picnic Beetles (Coleoptera: Nitidulidae),




Pennsylvania Department of Conservation and Natural Resources - Forestry , Bugwood.org




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. 



Also, a previous BYGL post by Amy Stone highlights facts about Oak Wilt




The purpose of this post is to promote winter pruning. While all oaks are susceptible to this fungus, those in the red or black group; black, pin, northern and southern red, scarlet, shingle and Shumard oak are extremely susceptible and can die within a few weeks of infection. 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.


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 is a perfect time to prune. In addition, many Arborists tend to have more availability at this time of year. Exceptions to only pruning in winter would be storm damage (ice or wind) and hazardous conditions of trees that can harm people or property when an arborist' workload can really increase.


A professional arborist will follow procedures to reduce the transmission of oak wilt.







The primarily 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.








If you have an oak that is already completely dead, you want to remove it if it presents a hazard to people or structures. If a tree has shown signs of decline, you may want to send a branch in for diagnosis at the OSU – Plant Pest Diagnostic Clinic. In order to diagnose oak wilt correctly the tree and the fungus has to be actively growing and present.




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.




In addition, if you have fears on whether your tree is or be at risk of falling, ISA offers credentials to arborists that have completed the Tree Risk Assessment Qualification (TRAQ). This is not for just 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.


Put it on your list, check it twice, schedule your arborists, so your OAKS LOOK NICE!