Jim,

I have seen Alternaria cause similar symptoms on hybrid poplars growing in wet conditions or too much shade. However, the impact is usually cosmetic. Has anyone attempted isolations? It also superficially resembles Bronze leaf disease (Apioplagiostoma populi) - but we didn't see such dramatic line patterns with it.

Those photos would make nice cover shots for Plant Disease some day!

Good luck.

Jason

Jason A. Smith
Assistant Professor of Forest Pathology
School of Forest Resources and Conservation University of Florida
134 Newins-Ziegler Hall
P.O. Box 110410
Gainesville, FL 32611-0410
Telephone: (352) 846-0843
Fax: (352) 846-1277
e-mail: jasons at ufl.edu <mailto:jasons at ufl.edu>
http://www.sfrc.ufl.edu/faculty/jsmith/index.html

-----Original Message-----
From: rg70200-forpath-bounces at lists.iufro.org [mailto:rg70200-forpath-bounces at lists.iufro.org] On Behalf Of James Worrall
Sent: Thursday, July 10, 2008 4:20 PM
To: rg70200-forpath at lists.iufro.org
Subject: [IUFRO RG 7.02 FORPATH] tiger blight?


We have a foliage disease of trembling aspen (Populus tremuloides) in southwestern Colorado, USA.  It is beautiful, strikingly unique, appears to be causing significant impact, and has me completely baffled.  The foresters who brought it to my attention are calling it "tiger blight"
because of the distinctive striping (see pictures below).  It is occurring mostly on suckers and saplings and lower branches of overstory trees.  I was told that in one regenerating stand of suckers, it is killing 30-40% of the foliage.

There is no fruiting (perhaps very early initials), but there are hyaline hyphae in the lesions.

If the striping is caused by alternation between night and day (and I can't think what else would lead to the zonation), the lesions appear to expand rapidly.

I put some leaves in a moist chamber to see if anything fruits.  In the meantime, has anyone seen this disease before, or even similar symptoms on another species?

(See attached file: tiger_4.jpg)
(See attached file: tiger_5.jpg)
(See attached file: tiger_group_1.jpg)

Thanking you in advance,

Jim Worrall

US Forest Service
Rocky Mountain Region
Forest Health Management
216 N. Colorado St.
Gunnison CO,  81230

(970) 642-1166  desk
(970) 209-1332  cell
(970) 642-1919  fax