By Lindsey Rice
ISA Certified Arborist® OH-6739A
November 6, 2025
Fall and cooler weather is here! With changing temperatures, all our trees are going to be going through a change as well. As we enter the dormant season, we will be gifted with vibrant leaf colors on all our deciduous trees. The dormant season doesn’t just refer to leaf senescence and the weather getting colder; disease-carrying insects also enter the stage in their lifecycle where they do not pose as big of a threat to our landscape. In recent studies it has been found that by October 15th (previously October 1st), the Nitidulid beetles that spread Oak Wilt disease will not be actively feeding in the Midwest, thus reducing the risk of infection with the fungal disease. Nitidulid beetles are insects that feed on the sap of trees. When a beetle feeds on the sap of an infected tree, it can move to a new susceptible oak tree and spread the disease. These beetles are most attracted to fresh open wounds, such as a new pruning cut.
All oak species are susceptible to the disease, but oak wilt is most damaging to the red oak group. The fungal infection causes xylem vessels to clog, leading the host of the disease to wilt and then die as quickly as within one growing season. Thus far, we have been unable to treat any infected oak tree with any success. We have treated some healthy trees in the area with a preventative fungal application, especially those close to a confirmed case of the disease.
Unfortunately, these beetles are not the only way that this disease is spread. It is also spread via root grafts of neighboring infected trees. Root grafts can connect oak trees underground and transmit the disease from more than 50 feet away. When there is a known infected tree in the vicinity of other oak trees, root disruption may be recommended, even after the infected tree and stump have been removed.
What can you do if you have Oak trees on your property? Be sure to have them pruned during the appropriate time of year between October 15th and March 31st. If you must prune an Oak tree outside of this window, ensure the wounds are sealed with latex paint to limit the beetles' ability to transmit the disease. If you suspect any of your trees have this disease, please call us, and we can advise you on the next step to confirm a diagnosis. Note that this is the same pruning window for Elm trees as well, so we may help limit the spread of Dutch Elm Disease.
Recently, we had ISA Board Certified Master Arborist® José Fernández, an oak wilt expert and a former RTE employee, visit our office and give a presentation on oak wilt disease to our arborists. Check it out down below!
Enjoy the colorful autumn season! For a free tree work quote by one of our 25+ ISA Certified Arborists®, visit RussellTreeExperts.com/Quote or call our friendly, local office staff at (614) 895-7000!
Please note: This article was updated on 11/6/2025, but originally published on 9/28/2023.
ADDITIONAL ARBOR ED ARTICLES!
Lindsey Rice | Operations Manager, Russell Tree Experts
Lindsey joined Russell Tree Experts in 2015 with a B.S. in Agribusiness and a minor in Horticulture from The Ohio State University. Growing up in northwest Ohio, she participated in various sports, band, and FFA which ultimately inspired her love for the tree industry. In her free time she loves to spend it outdoors with her husband and daughters.
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Additional Resources & Sources for this Article:
“New Disease Control Measures for Oak & Elm Trees” Article (2021)
“Oak Wilt in Franklin County” Article (2017)