Re: CULT: first casualty
- To:
- Subject: Re: [iris-talk] CULT: first casualty
- From: J* a* C* W*
- Date: Mon, 6 Mar 2000 21:43:17 -0700
From: "Jeff and Carolyn Walters" <jcwalters@bridgernet.com>
> From: Gullo <tgf@frontiernet.net>
>
> Might be an opportunity to see if any cultivars or
> species managed to survive the onslaught, and perhaps might be more
resistant.
> Could be useful information for hybridizing purposes. I wondered if you
grow
> any rebloomers, and if so, how they fared this winter.
Michael,
My experience has been that different classes of iris vary in the level of
risk that Botrytis presents to them. I have never had a case of Botrytis
infection in a beardless iris. Among bearded irises, Arilbreds are most
susceptible, followed by the regular bearded irises in order by size with
TBs most affected and no cases ever observed in SDBs or MDBs. While I
believe I have seen a difference among cultivars in susceptibility to
bacterial soft rot, it seems that all TBs are potentially susceptible to
Botrytis, and it is a matter of the luck of the draw which ones actually
are affected. For example, I have grown BEVERLY SILLS for over 15 years
during which time it has never before been bothered by Botrytis, but this
year a vigorous two-year old clump with multiple bloom size fans and
numerous increases has almost completely rotted out. On the other hand,
should it be considered mere coincidence that BS's white sport, BEVERLY IN
WHITE, is another clump that has been severely infected with Botrytis?
I have never made a big fuss over rebloomers, and consequently have not
enjoyed much rebloom, but last summer I dug all dozen cultivars I grow with
known reblooming tendencies and replanted them in a separate bed where I
can give them the special attention they are reported to respond to. None
of these is showing any sign of Botrytis. The ground they are in has not
been planted with irises for five years, but there are other irises, some
of them with Botrytis infection, growing only a few feet away. I did make
it a point of soaking everything I replanted last summer and all new
acquisitions in a 10% bleach solution for at least a half hour. So far, the
only newly planted/replanted TB rhizome that has shown signs of Botrytis is
one that I stuck in a hole in a bed that was left from a cultivar that
succumbed to Botrytis last year. Three replanted Arilbreds also have shown
signs of Botrytis, but as I have already said, Arilbreds have proven
extremely susceptible to this pest, and the infections in these cases are
much less severe than what I am seeing in the established clumps of TBs
that are affected.
> I've been doing some
> reading on salicylic acid ( aspirin ) and would suggest that trying some
might
> not be a bad idea to see if it helps control the Botrytis.
What dose rate, and how do you apply it? I'm willing to give it a try. The
problem with evaluating the effectiveness of Botrytis treatment is that the
fungus becomes inactive as soon as the ground dries out or the temperatures
rise above 40 degrees and stay there. Of course, it is a bit early to
expect either of those conditions to prevail here yet.
Jeff Walters in northern Utah (USDA Zone 4/5, Sunset Zone 2)
jcwalters@bridgernet.com
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