Hi Enrico,
Here is an updated contact for Rachael: Rachael - FS Sitz (rsitz@fs.fed.us). Rachael has just started as a research
plant pathologist with Rocky Mountain Research Station in Moscow, working with Ned Klopfenstein.
While I was a Forest Health Protection plant pathologist in southern California, Shannon Lynch’s project in the Eskalen lab was to work on determining causes of oak mortality and staining not attributed to sudden
oak death. Sandra examined some of the stained declining coast live oak attacked by the goldspotted oak borer, Agrilus auroguttatus, and determined that besides the many canker-causing fungi that were being discovered, Lonsdalea species (formerly Brennaria,
formerly Erwinia when I first starting in plant pathology!) were present. Sandra’s statement that black staining in oaks is often caused by Lonsdalea bacteria is also true for a number of other hardwoods with borer or other insect damage: Lonsdalea species
also cause staining in alder and walnut with insect damage. There seems to be a relationship with Agrilus species worldwide. Do you know if the red oak borer is present? This insect has long been associated with red oak decline.
Fusarium solani, Cryptosporiopsis, Phytophthoras, and other canker fungi often are associated with staining in oaks, but it is usually difficult to parse the contributions of the mix of organisms to determine
what is causing the staining. However, inoculations showed some of these fungi can cause black staining in inoculated oak seedlings without the presence of bacteria.
Here are some references.
Akif Eskalen or Shannon Lynch may be able to provide more details of the research findings on coast live oak and California black oak decline in southern California such as the mix of associated pathogens and
which fungal agents are most likely to cause black staining by themselves.
You may also want to contact Jason Smith, who is working on declines in additional oak species.
Paul
Paul
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Paul Zambino, PhD
Plant Pathologist
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Forest Service
Northern and Intermountain Regions
Forest Health Protection
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Caring for the land and serving people
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Dear Enrico
It is very good to hear from you, thanks for sending nice photographs.
Is this on Quercus robur?
I have seen very similar symptoms in the UK on Q. robur although weeps from the lower region of
stem branches. Although these type of symptoms are not typical of AOD (Acute Oak Decline), the cankers and weeps tested positive for the AOD bacteria and so we assign the cause of the cankers to bacteria.
Do you know if there is any insect association with the cankers in Ohio?
We could send you swabs, you could swab affected trees and post them back to us for RT-PCR assessment for AOD bacteria, if that is of help to you.
Additionally, there is an apparent emergence of Drippy blight in Colorado (Lonsdalea quercina). I think it would be useful to test for that in the case you mention in Ohio, it could
be important. Rachel Sitz and Ian Pearse are contacts for this expertise (Rachael.Sitz@colostate.edu; ianspearse@gmail.com).
I hope this is helpful,
Best wishes,
Sandra
Dr Sandra Denman
Principal – Oak Declines: Senior Pathologist
Centre for Ecosystems Society and Biosecurity
Forest Research
Alice Holt Lodge
Gravel Hill Road
Farnham
GU10 4LH
Hello forpathers and forenters,
Below are a couple of pictures sent to me by a local arborist, wondering what’s going on on the main limbs of a white oak. I am contacting you because I find that this kind of very localized bark discoloration/staining is quite
common in oaks. I’ve always suspected these were very small, localized infections by some species of Phytophthora, like citricola, citrophthora, etc. but I’ve never verified. Whatever it is, it seems to me it never goes anywhere, i.e. the lesions remain
very small and do not have any serious impact on the host.
Does anyone else actually know what these are? It would be of great interest to me personally, in addition to providing an answer to the arborist.
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Pierluigi (Enrico) Bonello Professor
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