Re: diseases of siberians
- Subject: Re: [sibrob] diseases of siberians
- From: B* H* <c*@cablespeed.com>
- Date: Tue, 02 Nov 2004 09:11:25 -0500
I agree with Ken. The work at Cornell was inconclusive. Scorch is a symptom
arising from the catastrophic loss of roots, not a disease in itself.
Potentially there can be several or many causes of root loss, so "scorch"
might be the common symptom of attack by a number of organisms. There was a
theory a few years ago (arising from work at Univ. Iowa with TBs) that
scorch is a disease caused by mycoplasmas (soft-walled bacteria-like
organisms), but it's not clear to me that this has been widely accepted. My
attempts over the years to have the causative agent diagnosed by
pathologists at Purdue and Michigan State have resulted in different
conclusions such as rhizoctonia, sclerotium etc. The problem is that these
fungi are surely present in the rotted roots, but they are universally
present in soils and may be secondary infections after the initial attack
has occurred and not the primary cause. As likely as not, more than one of
the complex of pathogenic soil fungi can cause this disease depending on
your location and past soil history. Two other points -- scorch is
generally an isolated phenomenon affecting just one plant in a group,
although it can be more widespread. Presumably something happened
underground to open up that one plant to infection. Second, it may be
possible to control the loss of roots with a soil fungicide if you can spot
the problem very early, but once the situation becomes obvious with
browning of the leaves, the roots are gone and it's too late. I have never
had success in saving a scorched plant and don't even try now, but someone
else may know how, in which case I'd be interested to find out! I hope this
helps. Bob
At 07:55 AM 11/2/2004, you wrote:
>Sharon, Juri & all,
> The technical work behind Currier's article was done here at Cornell
>University. I had a chance to talk to the professor in charge, Dr. George
>Hudler. (His background is in tree diseases). He was fairly negative
>about the report, basically saying that not enough diseased material had
>been provided to get to the bottom of the scorch problem.
> Personally, I have had a lot of trouble with root rot fungal
> diseases, and
>I have to wonder if some of the reports of "scorch" were in fact one of
>these.
> Ken
>
>
>
>
>
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