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The Search for a Tree Cure for Sudden Oak Death

By Ralph J. Zingaro, Consulting Arborist - Plant Doctor 

It all started in 1995 when Ken Bovero, a certified arborist with Marin County Arborists, called me in to a site in Kentfield, CA to look at some oaks and madrones that were dying. The site, which had been all too familiar with me, having studied tree decline complexes at Cornell University under the world's authority Dr. Wayne Sinclair. The trees were riddled with hundreds maybe thousands of beetles and were dying. This is the birthplace of "sudden oak death" the complex that has been called the "aids of the forest". This does have the potential to kill the forest as we know it. 

But it was not 1995, but 1982 when our native dogwood trees began dying in mass all along the eastern seaboard. It was déjà vu, it was a recurring nightmare that followed this New York native all the way to the West Coast. The cooperative extension of new york attributed the dieback to a fungus called anthracnose a leaf fungus that was clearly killing over 90% of all the dogwood trees. But the question arose, why is this fungus killing trees now, when it usually just makes leaves a bit unsightly? I decided to dig a little deeper, literally, and look at the soil. With the funding of a wealthy landowner of 500 acres on the North Shore of Long Island I began sampling the soils that these precious trees are growing in. What I found confirmed my suspicions that the soils had turned extremely acid and toxic aluminum, which is normally unavailable at higher ph, was killing the roots of these trees. At that time the Cooperative Extension was in essence creating a huge market for fungicide sales along the east coast. Even with this spraying the trees continued to die. I wrote articles about my findings and try to alert the forest service and cooperative extension with no success. After moving to Northern California 10 years later a friend sent me an article stating that the forest service had found that acid rain was killing the dogwoods and that the fungus was secondary. I felt good about that.

Now it was the native California Oak trees. Those graceful trees that line the coastline of Route 1. These trees were riddled with beetles and dying at a rapid rate. Ken Bovero and I alerted the Cooperative Extension of Marin. What followed after that was a series of nightmarish experiences for this career plant doctor. The cooperative extension of took the chemical line, they recommended a toxic termaticide to be sprayed on the bark of trees to kill beetles. This termite killer is only available to professional licensed applicators usually, but thanks the the Cooperative Extension, they began passing it out directly to homeowners. What followed was a deluge of toxic insecticide spraying throughout Marin and Sonoma and Coastal California. An insecticide that kills beetles but, as we later confirmed, did work to kill beetles but not save oak trees.

Then one day I went on a consultation in the heart of tree devastation country in West Marin. Another landowner with 500 acres hires me to research this problem because she is not convinced that beetles are killing trees. Again, I do a search of the literature and begin sampling the soil and leaves of trees nutritionally. Again I turn up severely acid soils, low phosphorous and high aluminum. During this period of time the "Oak Mortality Task Force" comes into being, I am a member of the "Treatment Committee". This was the group that was supposed to find a cure. What a joke, the self appointed head of the committee is the agricultural commissioner who only promotes more use of Astro or Dragnet insecticide. Any attempts to prevent the use of this insecticide is met with censure. Then UC Berkeley professor approaches me for collaboration.  We meet and then I share my findings and proceed to conduct experiments on what I know already, that a UC patented fertilizer called a phosphite will nutritionally boost a tree and save it.

To this day, this simple nutritional tool remains the only effective treatment for this devastating tree decline complex along with many others. To be continued...

Regards,
Ralph Zingaro, Consulting Arborist