Sudden Oak Death

3 05 2009

In recent years a whole lot of attention has been paid to Sudden Oak Death, a stem canker disease (Phytophthora ramorum) that has sickened countless oaks in California. I, too, believe that Sudden Oak Death is a particularly aggressive pathogen that requires our careful observation and study. To be sure, I often inspect the sick coast live oaks and tan oaks here in Big Sur and at least half have bleeding stem cankers.

Sudden Oak Death casaulty in Big Sur

Sudden Oak Death casaulty in Big Sur (photo by Lee Klinger)

Still, there are many other problems I am seeing in these forests that cannot be attributed to Sudden Oak Death. Pines are becoming infected with pitch pine canker, sycamores are sick with anthracnose, bays are toppling from a root collar fungus, and redwoods are losing their tops. It seems that something larger is going on . . .

I believe that the real problem is not pathological, it is ecological. This is a fire-adapted forest that is now deteriorating from years of fire suppression and neglect. The forest ecosystem is becoming overgrown and the soil is losing fertility. Add to that the occurrence of acid rain.

Hence, the use of  ‘fire mimicry’ techniques to improve the health of the ecosystem, aka Sudden Oak Life. By clearing the woody understory and fertilizing the soils we are attempting to resuscitate fire-adapted trees and forests.

Although we have had many successes with this approach (see Case Studies) there are situations where the trees are so sick and stressed that, despite all our efforts, they cannot be saved.

Consider case study no. 20041129.6 in Fairfax, CA where a bleeding coast live oak was treated in November of 2004. Leith Carstarphen of Ecologic Landscaping and Daniel Brooke of Arboright collaborated in the work on this tree (see North Bay for results of other oaks treated here). The photos below depict the sequence of changes in the tree’s canopy over the past four years. Initially, the infected tree seemed to be showing some improvement, as is indicated by the two-year photo below. But by year three an unexpected complication arose with construction of a new garage at the base of the tree. At this point the tree had begun to show some early signs of deterioration. By year four the tree appears to be all but dead.

sudden oak death

Sudden Oak Death (photo by Lee Klinger)

Photo caption: Coast live oak in Fairfax, CA, 2-yr results. Photo on the left was taken November 29, 2004, photo on the right was taken November 14, 2006 (Photos by Lee Klinger)

sudden oak death 2

Sudden Oak Death (photo by Lee Klinger)

Photo caption: Same tree as above, 3-yr results. Photo on the left was taken November 29, 2004, photo on the right was taken November 29, 2007. (Photos by Lee Klinger)

sudden oak death 3

Sudden Oak Death (photo by Lee Klinger)

Photo caption: Same tree as above, 4-yr results. Photo on the left was taken November 29, 2004, photo on the right was taken November 29, 2008. (Photos by Lee Klinger)

While the shock of construction probably hurt this tree, I have seen healthier oaks fare just fine under similar impacts of construction. I suspect that both the disease (Sudden Oak Death) and the construction were the proximal causes in the demise of this tree.

I take this oak as a reminder that many trees are simply too sick to be saved by fire mimicry or any other known treatment regimes. The obvious way to effectively deal with Sudden Oak Death is to intervene before the oaks become too ill.

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2 responses

6 10 2009
Dr. Heather Vallier

Hi Lee,

Let’s remember how virulent some pathogens are . . . I think that is why you may have gotten the negative responses you did from those in academia. This pathogen is a deadly killer, not a naturally occurring result of lack of fire, It was introduced through nursery stock from Europe where it devastated the Oaks.

In my humble opinion we need a “line” . . . and to educate the locals so they turn in suspect trees for examination. Let’s keep the communication flowing since we hold the same rope by different ends. I totally agree, as a plant pathologist, that healthy trees are less likely to become infected by any pathogen, however Phytophthora ramorum is not “any” pathogen. It’s a deadly killer and takes no prisoners . . . which brings us back to the “line”. Perhaps this ‘line’ is a fire mimicry in Big Sur?

7 10 2009
Lee Klinger

I appreciate your perspective and believe it is people like you who can help to bridge the gap between the epidemiology and ecology of sudden oak death. I do not disagree that sudden oak death is an especially aggressive pathogen. In my 2008 paper on sudden oak death I state, “There is no question that this disease is finishing off large numbers of coast live oaks and tan oaks”. Where I do disagree with the UC Berkeley/David scientists is whether the focus on treating and controlling the disease is the most effective approach. My view is that due to fire suppression the oaks are sick and predisposed to infection. Without a focus on fire or fire mimicry methods, the problem of sudden oak death will never be solved.

Let me also point out that there is still disagreement among the Phytophthora experts as to the exotic nature of sudden oak death (Phytophthora ramorum). I urge you to contact Dr. Michael Coffey, Professor at UC Riverside and curator of the World Phytophthora Collection, as well as Dr. Olaf Ribiero, co-author of the book “Phytophthora Diseases Worldwide”, to find out other professional opinions on this matter.

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