oak disease

[ScottF]

Bit stumped with this one. Looked at an oak the other day which had pushed a small section of a wall down after a wind, although it had been buckling the wall for years. Small leaves, weak extension compared to its neighbours and scatted dead wood.

The slightly puzzling bit was the blackened and slightly depressed bark near the base. I can't rule out fire, as it is in a little snicket where kids hang out, but ti just looks odd. There was a fairly weep at two point close to one another.

 

No fruiting bodies or obvious hyphae. Picus test revealed a fairly clean stem for the age and specie.

 

Any ideas?

[Fungus]

Looked at an oak the other day which had pushed a small section of a wall down after a wind, although it had been buckling the wall for years. Small leaves, weak extension compared to its neighbours and scatted dead wood.

The slightly puzzling bit was the blackened and slightly depressed bark near the base. I can't rule out fire, as it is in a little snicket where kids hang out, but it just looks odd. There was a fairly weep at two point close to one another. No fruiting bodies or obvious hyphae.

 

Scott,

Doesn't this blackening of the bark come from before present Hedera being ripped off at this side of the tree ?

[ScottF]

Hi Gerrit,

 

I removed the ivy when inspecting the tree, but the position of the ivy doesn't correlate with the position of the blackened bark. Did you mean, the bark damage precedes the growth of the ivy? I guess it must. The surrounding vegetation is cherry laurel thicket, all quite young and small diameter..

 

It's hard to see from the images, but the area of blackened bark is slightly recessed in relation to the surrounding bark. As I say, I can't rule out fire, as the associated root damage may cause the other symptoms (movement, small leaves, low vigour), and possibly a secondary infection with Armillaria, for instance (hence the early weep).

 

But then again, it just doesn't look "right".

Edited November 28, 2011 by ScottF

[Fungus]

Did you mean, the bark damage precedes the growth of the ivy? I guess it must.

 

Hi Scott,

No, I meant the rootlets of the Hedera attached to and uptaking water and nutrients from the bark caused the blackening and maybe also the slight depression.

[ScottF]

Hi Gerrit.

 

Perhaps, but as I said, the black areas don't correspond to the where the ivy was. That doesn't address the thick weep or the other symptoms though.

[MATTMOSS]

It looks like old fire damage to me.

[Fungus]

the thick weep or the other symptoms though.

 

You mean the black tar-like oozing from a crack in the bark at two thirds from the top in the first picture ? To me that looks like bleeding coming from an infection of the cambium with (rhizomorphs of) a parasitic Armillaria species. Does it smell of vinegar acid ?

Edited November 28, 2011 by Fungus

[ScottF]

Hi Gerrit

 

well, I went back to sniff the ooze, but the odour was fairly indistinct. It was, however, viscous, deep red-brown and fairly sticky. Attached is a close-up of the weep, plus a possible dried weep (brown light crust) just to the left of the ooze proper.

 

I had a bit of a look around and about three metres from the oak was a standing dead cherry laurel. The tree has been dead for some time and there is a black deposit (possibly a Hypoxylon sp.?) on the stem. The sample is attached.

 

There are no other dead or diseased trees nearby. Yes, Matt, I think that fire's involved, but I'm now trying to get to the bottom of the knock-on effects in terms of disease entering the damaged wood and roots, and it's significance.

 

Cheers

[Fungus]

1. It was, however, viscous, deep red-brown and fairly sticky. Attached is a close-up of the weep, plus a possible dried weep (brown light crust) just to the left of the ooze proper.

2. The tree has been dead for some time and there is a black deposit (possibly a Hypoxylon sp.?) on the stem.

 

Hi Scott,

1. The long vertical crack oozing on top and at the bottom does look like an indication of the presence (of rhizomorphs) of Armillaria to me.

2. The black deposit is not of fungal origin, but looks like burned (charcoal) bark to me.

[ScottF]

Cheers, Gerrit.

 

I think that all adds up. Fire vectoring armillaria through boiled roots, essentially.