Diseased oaks?

[Jehinten]

I was recently called to a home where an oak tree lost a 50' limb roughly 13-14" diameter at the branch union. The tips were hung up in the top of a Box Elder and the butt of the limb was resting where it broke off with maybe 2 square inches of wood holding. Got it down with no problem but noticed that all 5 oaks in this backyard had similar wounds and many were right in the branch collar although some were in the middle of the limbs. Any thoughts as of the cause? I did notice one limb, roughly 4" diameter that all of the bark was off of the top of the limb for maybe 5', if that's related. I didn't get a picture of that one.


My ID on this kind of stuff is pretty much non existent, so I appreciate any help. In addition, what should be done once the cause of this has been identified. Should they expect future limb failures at this point, or was this just a coincidence?

 

[Brando CalPankian]

They look pretty vigorous. I don't know if so much diseased as damaged. Maybe a storm a while back took out some trees/limbs and things that tore up those sections. It looks like rub damage/abrasion to me, but I could be wrong. I've seen mammals cause damage like this too, though nowhere near to that extent. Sun scald from overpruning could have caused or contributed as well. Would love to see what others chime in with.

Climb high!

 

[Jehinten]

They look pretty vigorous. I don't know if so much diseased as damaged. Maybe a storm a while back took out some trees/limbs and things that tore up those sections. It looks like rub damage/abrasion to me, but I could be wrong. I've seen mammals cause damage like this too, though nowhere near to that extent. Sun scald from overpruning could have caused or contributed as well. Would love to see what others chime in with.

Climb high!

I forgot to mention, the leaves actually looked good (no wilting or spots) and they did have full canopies apart from some old storm damage in two. Those two look like they'd lost their tops some time ago. The other three do not appear to have lost anything major.

There are a number of dead limbs in these canopies as well, but not really concerning. In that regard they simply look like neglected trees and a deadwood trim would improve them greatly.

I appreciate your insight, the amount of damage that I'm seeing at the branch collar makes rubbing seem unlikely. I have seen what I believe to be damage from squirrels in other trees, but most of that was on top of limbs and not under or in collars like this.

 

[The Green One]

This link may have some answers.

Branch shedding in trees

The shedding of lateral twigs and branches is a frequently-observed phenomenon of woody plants. Millington & Chaney (1973) outline two distinct mechanisms by which a branch may be shed: (1) phy…

arboriculture.wordpress.com

 

[Serf Life]

@KTSmith any ideas?

 

[KTSmith]

Thanks Serf Life for the call out!
Entirely consistent with Strumella canker, although perhaps not obligately so. A good description of the disease is in Dave Houston's 1966 article here. I don't have the Sinclair and Lyons text here at my home office, so I can't check that. There are often multiple rounds of woundwood production, and may or may not appear in concentric rings (as the case with Nectria canker).

Given the description in the original post, I'm leaning hard on Strumella. Although not particularly encouraging, the linked article probably is still correct in stating that infected trees do not recover and that for stands managed for timber, sanitation removals are called for.

 

[Brando CalPankian]

I stand corrected. Great information! Thank you for sharing!!

 

[KTSmith]

Thanks for the opportunity to cite a Dave Houston article. He was Alex Shigo's supervisor in the FS in the early 1960's, and had a big hand in Shigo's early Forest Service publications. Curiously in turn, I worked with Dave on Sapstreak Disease of maple in the 1990s and was Dave's final FS supervisor as he was finishing his government tenure in the early 2000s. Last I heard, he was still working during the summers on beech bark disease throughout the northeast US and Canada. Hope he's still at it, anyway!

 

[Serf Life]

Very cool, it looked similar to one of the Nectria cankers but not quite right. Some have that defined target and some look like enlarged beech bark cankers but this is new to me. Also pretty neat to see on the branch undersides attacked and not much on the trunk.

 

[guymayor]

Thanks Serf Life for the call out!
Entirely consistent with Strumella canker, although perhaps not obligately so. A good description of the disease is in Dave Houston's 1966 article here. I don't have the Sinclair and Lyons text here at my home office, so I can't check that. There are often multiple rounds of woundwood production, and may or may not appear in concentric rings (as the case with Nectria canker).

Given the description in the original post, I'm leaning hard on Strumella. Although not particularly encouraging, the linked article probably is still correct in stating that infected trees do not recover and that for stands managed for timber, sanitation removals are called for.

When you say infected trees do not recover, does that still allow for a kind of standoff, where the tree grows enough new tissue to compensate for the lost tissue? So in landscape tree terms, it could be quite reasonable to retain?

 

[KTSmith]

Thanks for the prompt, Guy. I missed an opportunity here, for which I will attempt to recoup:

In my observation and with reference to established forest pathology research, trees with Strumella Canker Disease do not "grow out" of the diseased condition. But yes indeed, a standoff does occur over some years. The roughly-perennial nature of the cankers shows that infected parts do remain functional and contribute, to some degree, to the welfare of the individual tree.

I should also hasten to say that management recommendations ought to depend on the goal or intent of the land manager. Most all of the written stuff on this disease comes from native secondary/tertiary forests managed for timber, so may be most applicable to folks with those goals. Management for wildlife or for the urban/community environment? There is a great research topic!