In June of 2022 I was asked to determine why the oak tree in the picture to the left that was located in Liberty Park in Sedalia, Missouri was rapidly dying. Once arriving on site, I saw that this tree was defoliating and had large sections of recently dead branches in the tree. There a were also several like tree across the road from this tree that were dying in the same manor.
I then went home and did some research and found that it was possible that this tree was dying of Oak Wilt. Oak Wilt is a fungus that arrived in the United States in at least the 1940's from likely South America. This fungus affects all trees in the Beech tree family which includes all oak trees. This fungus spread when beetle in the Nitidulid family land on Oak Wilt fungal mats, get the fungal spores on them and then fly to open wounds in surrounding trees or by the intertwined roots of infected and non-infected trees. The fungus then clogs the water moving xylem cells of infected trees as the fungus feeds on the sugars in the tree. Oak Wilt infection can only be prevented with fungicide infusions in oak trees (TexasOakWilt) of the red oak sub-family which includes pin oaks, northern red oaks and shingle oaks. Once infection occurs in these red oak trees, they can rapidly die sometimes within a growing season. While oak tree in the white and live oak sub-families can be infected with Oak, they can be therapeutically treated with fungicide infusion but will die if they are not treated. this death will just occur in a longer time as compared to oaks in the red oak sub-family. I also need to note that as of right now, only trees in the red oak sub-family, bur oaks, and white oak are known to make fungal mats which can lead to over ground spread by beetles. They trees should be prioritized for early removed when diagnosed so they do not make fungal mats as they die and lead to long distance over ground spread.
During my research about Oak Wilt, I found a website by Kevin Belter, ArborCare & Consulting - Oak Wilt Experts (arborcareandconsulting.com) and that has become the basis of my knowledge of Oak Wilt. I also began to rely on information from the Texas Oak Wilt Partnership ( TexasOakWilt ). Though Oak Wilt was first found in the northern states of the United States, I find the information out of Texas better fits Missouri as we have like thin, rocky soils, and climate.
Based on Kevin's advice on his ArborCare and Consulting site, I took samples from the tree I was first sent to diagnose and shipped the sample to Research Analysis Laboratory, Research Associates Laboratory (vetdna.com) to be properly diagnosed to determine if this tree indeed had Oak Wilt.
This test came back positive, and I was now off and running to find where else around me were there trees infected with Oak Wilt t Missouri Arborist Company, we take a personalized approach to tree
I soon learned how to determine the signs of Oak Wilt in trees and sent dozens of samples in for DNA testing. Most of which came back positive for Oak Wilt. I tracked these cases in a ESRI Survey 123 Form (Oak Wilt Map - Data (arcgis.com)). In 2024, this has become a huge passion project for me as I am currently seeing more mature oak trees die from Oak Wilt infection then mature ash trees dying from Emerald Ash Borer. This is scarry to me because the more I learn about Oak Wilt, the more I see that our state agencies and labs like the MU Lab, do not know about Oak Wilt.
Unfortunately, I have learned there are so many dangerous misconceptions about Oak Wilt in Missouri. These misconceptions and false information are mainly coming from the Missouri University and their Laboratory. Generally, this information if based on the MU Lab not being able to positively confirm Oak Wilt during their testing process. The lab there uses cultivation process where they attempt to grow Oak Wilt fungus from samples that are sent in. This process gets many false negatives as Oak Wilt fungus dies at around 90 degrees and I believe the fungus often dies in shipping before the lab receives the samples. Based on my DNA testing of white oak trees in Missouri, I believe these false negatives have happened to such a degree that MU has labelled white oaks dying on Oak Wilt as White Oak Decline. To solve these issues, DNA testing needs to become the standard of testing for Oak Wilt.
The University of Missouri and its Assistant Extension Professor and Director of the MU Plant Diagnostic Clinic, Ph. D. Peng Tain, has stated publicly at 2024 Pesticide Applicators Recert Program and in this document on Oka Wilt ( oak-wilt-disease.pdf (missouri.edu) ) that " Some companies offer treatment by fungicide for infected trees, but the efficacy of these techniques is subjective and have not been studied clincially, so the results may vary." This statement is false and when I brough up several studies:
Appel, D.N. (1990). The use of propiconazole for control of oak wilt in live oak. Phytopathology 80, 976.
Appel, D.N., Kurdyla, T. (1992). Intravascular injection with propiconazole in live oak for oak wilt control. Plant Disease 76, 1120–1124.
Blaedow, R. A., Juzwik, J., & Barber, B. (2010). Propiconazole distribution and effects on Ceratocystis fagacearum survival in roots of treated red oaks. Phytopathology, 100(10), 979-985.
Juzwik, J., Appel, D. N., Macdonald, W. L., & Burks, S. (2011). Challenges and successes in managing oak wilt in the United States. Plant Disease, 95(8), 888–900.
Wilson, A. D., & Lester, D. G. (1995). Evaluation of propiconazole application methods for control of oak wilt in Texas live oaks. Fungicide and Nematicide Tests, 51, 389.
Dr. Tain wrote me that he would " I will consider your comment and refer to 2-3 forest pathologists from other land grant universities to peer review this publication later this fall." While it is good that Dr. Tain is willing to appeal to peer consensus, it is alarming that no one at MU looked up the Texas Oak Wilt Partnership's website and had seen the Oak Wilt Studies under the research tab before stating the ineffectiveness of fungicide that was invented in 1979 and has been used in the suppression and control of Oak Wilt since 1990.
The Missouri Department of Conservation ( Oak Wilt | Missouri Department of Conservation (mo.gov)) , University of Missouri ( oak-wilt-disease.pdf (missouri.edu) ), and Missouri Botanical Garden ( Oak Wilt (missouribotanicalgarden.org) ) all state that the pruning of oak trees in Missouri should not take place between April and either late June or through July due to this time being the height of Nitidulid beetle activity which cause Oak Wilt over ground spread. All these groups then mention painting would with paint to seal the wounds if pruing must occur during this time. While this is decent information, it is not the right information.
Indeed, the height of Nitidulid beetle active is at this time, these beetles are still active throughout the year and fungal mats on oak trees do form other times during the year outside of the only occurring in spring (nc_2005_ambourn_001.pdf (usda.gov) nc_2005_ambourn_001.pdf (usda.gov)) ( Oak Wilt Fungal Mats | ArborCare & Consulting (arborcareandconsulting.com)).
What is the right information, Oak Wilt fungal mats are present all year long, the beetles that carry Oak Wilt are active all year round, so infection can occur anytime during the year. Due to this painting wounds should occur all year round.
Here is a common example that happens because of the bad information MDC, MU, and the Missouri Botanical Garden put out; tree companies throughout Missouri schedule oak tree pruning in the winter and do not paint cuts. Then because these trees are dormant, the sound they make do not seal and stay open throughout the dormant season. We then have a hot spell in February or March, beetles wake up and fly, Oak Wilt fungal mats form, and poof, the trees you just opened wound in throughout the winter are susceptible to infection.
As all Arborist know, the best time to prune trees is in the spring when they are most active and seal wounds the quickest. Based on this, there is a good argument to pruning oaks in the spring and painting them for the best protection from Oak Wilt. Where this should be the standard is up for debate, but painting wounds all year long is not, it must be done.
There are many things we can do to address Oak Wilt in Missouri. First, we need to make DNA testing the standard for Oak Wilt diagnosis. We need to alert of Municipal organizations to the presence of Oak Wilt via mapping. We need to have it become a standard to have tree workers paint wounds in oak trees all year long. Fungicide infusion need to be recognized as effective treatments and prevention tools by the University of Missouri and other state agencies. We need to remove dead or dying oak trees as soon as possible and state or local grants to help people do this who cannot afford to do it by themselves. We also need to recognize the signs of Oak Wilt infection in specific oak species in Missouri. I will attempt to do this in the final section of this page.
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