From: heilmayr@jaffna.berkeley.edu (Klaus)
Subject: Re: Rust on Roses (chemical angst)
Date: 31 May 1993 08:32:06 GMT

savage@capella.cup.hp.com (Deborah Savage) writes: 
|>Does anyone have any "organic" methods to treat rust on roses?

Safer makes a "Garden Fungicide" that's supposed to be effective on
rust, black spot, powdery mildew, etc.  I haven't tried it yet, but I
may have to soon.  It's some sort of sulphur-based spray and, like all
Safer products, it's supposed to be less toxic than the usual bunch of
chemicals.

The latest issue of the Heritage Rose Group's Rose Letter also
describes a fungicidal spray that (in research at Cornell) has been
shown to be effective on black spot, powdery mildew, and other fungi.
It hasn't been tested on rust yet, but it may be worth a try.  The
formula is:
- 1 Tablespoon baking soda
- 2 1/2 Tablespoons horticultural oil
- mixed with one gallon of water
Spray weekly.  (note: higher concentrations can damage foliage, so use
the indicated proportions) Apparently, you need to use an oil with a
high UR (unsulfonated residue) rating -- 92-99%.  The brands that were
specifically recommended were Sunspray Ultra-Fine Spray Oil and
Superior Horticultural Spray Oil.  Both are available from Gardens
Alive (which was mentioned by a previous poster).  To find a local
source of Sunspray, you can call the manufacturer, Microgen Corp., at
(800) 745-7476.  Note that the Safer fungicide says on the label that
it should not be used for 4 weeks after the use of an oil spray.

Two more solutions that were suggested for black spot (but not for
powdery mildew, so they're probably less likely to work for other
fungi like rust): Spray with an anti-transpirant (Foliocote and
Wilt-Pruf brands seem to work).  Spray with a solution of baking soda
and a spreader-sticker ("Tween 20" brand).

Well, that's all the information I can find right now.  I hope
something here works for you.