oak wilt

[Kevin]

How do you diagnose oak wilt with any certainty?
Is there a remedy?
Someone on another forum suspects their tree has it and has opted for a wait and see what happens approach.

 

[Nathan]

Alamo from Novartis has varied results depending on species involved.

Symptoms vary. Here, live oaks usually have very textbook, identifiable symptoms. Red oaks have an easy symptom - DEATH.

 

[Babberney]

The most reliable way I know to diagnose is to take a tissue sample (either a section of 2-in diam branch or a "bark window" taken from the trunk) and send it to the lab. Here, it goes to TX A&M usually. They culture the tissue and see if they can grow any of the fungus. A negative result is not a guarantee of no infection, but a positive is generally pretty positive I think. Here's a link to A&M's site that answers all your questions:
http://plantpathology.tamu.edu/Texlab/oakwilt.html

As for treatment, it's like Nathan said. Some trees (especially Q. fusiormis, Q. virginiana) respond to Alamo injections and some don't. Earlier treatment increases chance of survival. The big concern I have in this case is the leave it and see approach. If this tree is infected, it should be treated or removed, adjacent trees should be treated, and a tyrench may be in order to prevent further spread by root grafts. If it is a red oak (Q. shumardii, Q. falcata, etc.) it should be disposed of at a landfill so it cannot culture the fungus and spread new spores (fruiting mats don't appear in live oaks or white oaks).

good luck,

Keith

 

[Kevin]

Thanks, I'll pass it on, I've already suggested having a certified arborist look at it and thought some testing could be done on the tree but wasn't sure.

 

[mquinn]

i'm really skeptical about the trenching idea, keith. i know that's what's recommended, but as i've seen it practiced and the justifications spelled out, i see it as a big expense with a low payoff. when i first heard about it several years ago, they were recommending a certain radius from the infected tree that had increased by several hundred feet from their original recommendations. i suspect that problem lies in the avenues of spread, and the variability of the rate of spread, connectivity of roots, variability in trees affected, etc.

another possible concern with the trenching idea is in the idea that the infection in the remaining roots is no longer being 'pulled' into the infected tree, and so is more quickly pulled into the healthy tree. i don't know about that - whether there's any research to back it up, or whether it's just somebody's idea of what might happen.

anyway, i'd not recommend trenching, generally speaking. i don't think it's well proven/correlated with prevention of spread of infection. you're cutting the roots of the healthy tree in the process, making nice infection ports. and the trench isn't particularly wide - i'd suspect it would encourage regrowth of roots in that area as well.

of course, i'm not crazy about injections either, but they make more sense to me than trenching.

 

[Babberney]

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i'm really skeptical about the trenching idea, keith. i know that's what's recommended, but as i've seen it practiced and the justifications spelled out, i see it as a big expense with a low payoff.

[/ QUOTE ]
Yes, I hear you, M. I'm also skeptical, especially after a meeting I attended with David Appel as the speaker. He told us about a test project where trenches were dug (to 48", I think). Later, after the infection spread across the trench, they dug deeper and found grafts below teh trench. Even clients with money would struggle with the cost of a five- or six-foot trench. I repeated it because, as you said, it's the current "accepted practice" and because you can be pretty sure of the result if you do nothing. That comes a little too close to saying we should do anything just to look busy, but I do not intend that to be my point. We do know root grafts are one vector of the disease and, despite my skepticism, in theory trenches make sense.

I've also heard the theory about how cutting the connections helps the fungus to spread into a new tree. I can't remember any more than you about when or where. I hope someone will find a source (or do new research), but in the meantime I'm back to the recommendations of the aggies, and , by extension, every other organization in the state that's offered an opinion on the matter, which is to trench if you see an infection heading your way.

 

[Nathan]

Dr. Appel got me my first job with a tree service. Important thing to remember is he is a fungus man, not a tree man.

I can see both sides of the trenching issue. One thing I have seen here in Austin is an entire block trenched around. Seems to have worked because years later, wilt creeps around the inside of the block but hasn't jumped out.

It is all a bit of voodoo science in that there is a lot they don't know. Ceratocystis fagacearum comes in many different varieties. Injecting has no effect on some varieties.

The important thing to remind a client with oak wilt on their property is that they are dealing with a damage control situation and not a heal and cure situation....

 

[mquinn]

hmmmm...well, of course i don't know austin's blocks, but if there's a large enough expanse of road and walk between trees in the infected block and the surrounding blocks, i'd wonder whether trenching made any sense there, either. do you have narrow streets and large trees that are likely root grafting beneath them?

one idea for trenching that seemed more logical to me was that of having concentric trenches, but it still seems like an unproven, expensive approach. i don't know the research, but i suspect there weren't a whole lot of repetitions &amp; comparison controls - just given the sheer amount of acreage and number of trees that would be required to make a study like that. i know you guys have plenty of acres of oak wilted trees down in that area, as i've seen them first hand - but given the information on the trenching research that i got from appel when he was in minnesota a few years back, i'm not at all convinced the method is justifiable.

i could be missing something.

nobody's going to want to hear it if they're trying to save their oaks, and it's not a standard recommendation of mine to just leave it alone (but one day it will be). stepping back and looking at the bigger picture, the vast numbers of oak wilting trees join other 'epidemics' in both the plant and animal kingdoms that are moving through our world quite rapidly in recent years, and are all part of the changing face of the planet - an evolutionary leap if you stand back and take the long look over the whole picture. it won't be stopped by our efforts and arguments. but we'll make them just the same, since our livelihoods depend upon them.

 

[Nathan]

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it won't be stopped by our efforts and arguments. but we'll make them just the same, since our livelihoods depend upon them.

[/ QUOTE ]

exactly, but how else are we supposed to sell fear and Alamo??......