[nafex] FW: Q. imbricaria bronzing disease

["Lon J. Rombough" <lonrom@hevanet.com>]

Has anyone in the midwest observed this?
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From: GUY STERNBERG <GSTERNBERG@DNRMAIL.STATE.IL.US>
To: L-QUERCUS@LISTS.PSU.EDU
Subject: Q. imbricaria bronzing disease
Date: Thu, Oct 12, 2000, 8:38 AM


Dear Quercus-list members:

We have been observing a disease of Quercus imbricaria here in central 
Illinois (Menard and Sangamon counties) for the past three years. The first 
conspicuous symptom is a zonal/marginal bronzing of foliage scattered 
throughout the crown in late summer, resembling fire scorch or early 
symptoms of oak wilt. The following year, the bronzing increases, some 
branches die back, and epicormic sprouting begins. The disease advances 
further the next year, resulting in death of the tree. Affected trees are 
randomly distributed among healthy trees.

The University of Illinois has not been able to culture oak wilt from 
specimens. In addition, the disease cycle lasts for at least three years, 
which pretty much rules out oak wilt in a red oak species, and there are no 
infection circles involving spread of the disease via root grafts.

Xylella fastidiosa scorch has been suggested as a possible cause, but the 
characteristic "wet" zones at the margins of necrotic areas are missing. No 
bioassay for Xylella has been done at this point, but we will have it done 
if nothing else can be suggested as a more likely pathogen.

Has anyone else on this list serve noticed this problem?
Can anyone offer any suggestions?

Please copy your responses to pathologist Nancy Pataky at the University of 
Illinois Plant Clinic (npataky@uiuc.edu) and to anyone else you feel should 
be involved.

Thanks - -
Guy Sternberg
Starhill Forest
Route 1, Box 272
Petersburg, IL 62675 USA


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