Folks (and particularly Mike Albers),
Very interesting! I really have no idea, being for the most
part a Pathologist in Florida dealing primarily with pines. As a
pathologist, a thought comes to mind, but you should try to verify even
the possibility of this with someone who deals with oak wilt (caused by
Ceratocystis fagacearum). You are (as I understand it) in an area where
this disease occurs, and red oaks are susceptible hosts, often
displaying vascular staining or streaking. Most of the time infected
red oaks die, but I do know that if infections of some vascular wilts
are not lethal, recovery can occur, sometimes "compartmentalizing" the
pathogen in interior vascular tissues - together with its associated
vascular staining. Any chance that these trees might be oak wilt
survivors? This could possibly be evaluated in a laboratory.
Ed
________________________________
From: rg70300-forent-bounces(a)lists.iufro.org
[mailto:rg70300-forent-bounces@lists.iufro.org] On Behalf Of Mike Albers
Sent: Thursday, November 19, 2009 11:44 AM
To: rg70300-forent(a)lists.iufro.org
Subject: [IUFRO RG 7.03 FORENT] Fwd: Dark rings in red oak logs
Any idea what would cause dark rings in red oak logs as in the attached
pictures?
The dark rings run the length of the logs. So far this has been seen on
a number of sites in 3 or 4 counties in Minnesota. Not all red oak
trees on a site have the dark rings.
My first guess is that it is a barrier zone resulting from a wound or
injury of some type. However it seems strange that it forms a complete
cylinder that reaches the ends of the logs. I didn't see any logs where
the dark ring only went part way around a log. Also there were some
logs that had obvious injuries with decay and discoloration but these
logs did not form rings or even have distinct barrier zones going even
part way around the log.
I've only looked at logs like this while in the mill, not on the site
where they were harvested. At first, the thought was that these rings
were the result of something happening 16 to 17 years ago. This will
take more investigation, but it looks to me like the time period varies
anywhere from 6 to 35 years. Also at this time I can't say if the time
period varies ibetween sites, or if the time period varies from log to
log on the same site.
Any suggestions would be appreciated.
Mike Albers
Forest Health Specialist
MN DNR-Forestry
1201 E. Hwy. # 2
Grand Rapids, MN 55744
(218)-327-4115