Subject: Re: Black spot on roses
From: "Bill Robinson" <roseguy@flash.net>
Organization:
Date: Tue, 03 Nov 98 10:45:37
Message-ID: <MOD$981103.1091@rec.gardens.ecosystems>



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. Two points: 1.) "Organic" gets defined in
a number of ways. The way that it is used in the
Faq is that it means that the material is environmentally
friendly and that when the material is used on crops
labeled as being "organic" or is used on land used for the
raising "organic" crops that it is certified as "organic by a
certifying agency such as the Organic Crops Improvement
Association. Wilt-Pruf is a mixture of polymers similar to
those used in the manufacture of water-based paint and
they are not permitted for use on certified organic crops.
When used as directed, they are not much of an environmental
problem as they bio-degrades fairly rapidly and they are not
particularly toxic, but they probably shouldn't be considered
as "organic";

2.) Lime-sulfur and agriculture sulfur have been in use as fungicides
for over a hundred years and they are righteously effective in the
prevention and control of black spot on roses. This use is cleared by
the USDA and both sulfur and lime-sulfur are permitted on certified
organic crops by the Organic Crop Improvement Association. They
have an established record for being both effective and environmentally
friendly.

I've done studies with sulfur, lime-sulfur, Wilt-Proof and most of the
various commercial synthetic fungicides on roses. Of all the fungicides
around,
lime-sulfur or plain agriculture sulfur gave the best results in terms of
controlling black spot. They are just such buggers to use!

One of the skeletons in my closet is that I am a bio-chemist by formal
training and worked as an agricultural chemist for one of the really big
agricultural chemical companies for many years. Its not something I'm
particularly proud of. . . . I used acrylic polymers similar to those in
Wilt-
Pruf to extend the service life of malathion on cotton. I also tried using
small quantities of plain paraffin which worked even better.

Second point. There have been studies at Texas A & M with some of the
old China roses that have shown that susceptibility to black spot is a
function of the genetics. These studies were mentioned a couple of years
ago at an Old Rose Symposium at the Huntington Botanical Gardens.
Specifically, it was said that some of the old China roses simply aren't
subject to black spot and work was going on to hybridize this quality into
other roses.

The blanket statement that all roses need to be sprayed with a fungicide
to prevent or control black spot just doesn't wash. The best all around way
to deal with black spot is to use black spot resistant roses and to keep
the garden clean.

Bill

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