Subject: Re: Black spot on roses
From: <godfatha@hotmail.com>
Organization: Deja News - The Leader in Internet Discussion
Date: Thu, 05 Nov 98 18:36:42
Message-ID: <MOD$981105.27404@rec.gardens.ecosystems>
References: <MOD$981103.1091@rec.gardens.ecosystems>
In article <MOD$981103.1091@rec.gardens.ecosystems>,
"Bill Robinson" wrote:
>
> Apparently the issue of black spot on roses is a continuing theme of
> interest. Here's a couple of
> more things to add to the talks.
>
> The Godfatha talks about the use of Wilt-Pruf
> as the only organic fungicide with an effective
> record.
I don't want to prolong this because we apparently have some basic
disagreements, but I do want to reply to some of your points.
If you want to use a fungicide material because some organization has
"certified" it as organic, you are free to do so. Not for me, however.
I'll specifically address the two you mention. Lime-sulfur has a very low
LD50, lower in fact than many powerful chemical insecticides. That makes it
a serious poison, and I won't have it around. Others can decide for
themselves.
Sulfur has been shown to be highly toxic to beneficial predatory mites. I
find it contradictory to use a material as a fungicide when it is so toxic to
beneficial animals. Again, that's a decision each must make.
I'm not going to address the historical-organizational arguments.
Obviously, they don't carry any weight for me.
So I guess we must agree to disagree.
> The blanket statement that all roses need to be sprayed with a fungicide
> to prevent or control black spot just doesn't wash.
I don't believe I said or implied this, and I certainly don't DO it. For the
reason that my roses were selected so they can grow without needing
fungicides at all, "organic" or otherwise.
What I did say is that all roses get blackspot. Of course, that only means
the roses I'm familiar with, but that is a very wide representation, and
includes those species roses and simple crosses which are called
"disease-free". In this context, "disease-free" really means "doesn't
usually defoliate". For example, Rosa chinensis, the ancestor of the China
roses, does get blackspot, but it keeps most of its foliage in most years.
That's a big difference, and one of the reasons why a lot of the rose
literature is misleading.
>The best all around way
> to deal with black spot is to use black spot resistant roses
Certainly true, but how does one know? Especially when the recommendations
are so obviously driven by local climate and weather (and even growing
conditions). The best one can do is to search out a local grower who truly
does grow roses without fungicides. Don't go to your local rose society or
botanical garden, because you won't find them there (usually).
I'd be glad to tell people the roses that I grow. I'm not claiming that they
are disease free or resistant, just that I don't use any fungicides on them.
But maybe that wouldn't work out in other climates and I don't want to add to
the problem.
>and to keep
> the garden clean.
Ah, yes... the old "sanitation" pitch. Actually, sanitation is fairly
effective as part of a MANAGEMENT strategy, but it isn't going to eliminate a
disease.
Again I feel the literature is somewhat misleading about management vs.
elimination. If we insist on growing roses, we are going to have diseases.
If we grow resistant ones, we will have less. If we grow susceptible
varieties, we'll have more.
Thank you for an interesting discussion.
--
**The Godfatha**
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