Re: CULT: Crown Rot(s) and Southern Blight

From: John Montgomery <monashee@junction.net>

 Anner wrote:

> How curious. We have a crown rot here in the Southern US as well. Probably
> several of them if the truth be known, but one in particular which is very
> distinctive, very destructive and not specific to irises. What it can do to
> columbines or hostas would make you weep and it just carried off my Clematis
> montana. Our rot is called Southern Blight, or Mustard Seed Fungus. It is so-
> called because, after the fine white webbing which forms across the soil and
> and crown of the plant----the active fungus----begins to go quiescent, it
> forms resting bodies that resemble mustard seeds. Little spherical things.
> First they are blond, then they eventually turn darker brown and in this state
> they can  inhabit the soil for years awaiting advantageous conditions. The
> soil-borne pathogen involved is the fungus Sclerotium rolfsii and it enjoys
> high humidity, poor dainage, and poor ventilation, but the activating factors
> are heat and moisture. It can carry off either bearded or beardless irises and
> is to be taken very seriously. The only fungicide I know that is effective on
> the disease is Terraclor, applied as a drench. Bleach will kill it on a
> rhizome lifted from the ground, but not one in situ. I wonder if this is the
> same fungus found in the antipodes?
>
> I noticed that the April issue of the AIS Bulletin had an article on disease
> control, but in this article whereas Subdue was recommended for Crown rot-
> pathogen unspecified--on beardless irises, Terraclor was recommended for
> Botrytis. I would reverse these prescriptions, myself, so I wondered if anyone
> had any new information on this point.

I had this fungus years ago. It is not normally present at these higher
latitudes
and arrived on a shipment of iris. After consultation with our Provincial
Horticulturist, he brought me a reprint of research done at Oregon State Univ.
on
soil solarization. The findings were that solarization was a more effective
control of Sclerotium rolfsii than any fungicide available at that time.

After disposing of the rhizomes I got out the poly and gave the soil a good
heating. Since then we have had no problem. Now that may also be due to the
organism not being able to survive or winter. In any event, that was my
initiation
to soil solarization and I am a believer.

Sincerely

John Montgomery
Vernon  BC  Zone 5
email:monashee@junction.net




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