I've used neither and information received from others tells me that organic fungicides are relatively ineffective.

Didn't work for BS in my climate. What disease is the main problem in your garden? Based on my experience it is easier to control PM oraganically than BS. But, I live where PM is not a big problem, so take it with a grain of salt.
Olga

Powdery mildew. Also in the backyard are Phlox paniculata 'Starfire', which get it by the end of summer, and 'Jacob Cline' bee balm, which got it early last year, as it truely needs to be dug up, divided, and the soil amended. I've never bothered to spray,as it's always been so late in the season by the time the mildew showed up. I'm thinking I should now, if I'm going to grow roses.

Powdery mildew can be controlled by a number of organic fungicides, including sulfur, copper products such as Soap Shield, baking soda or its kin potassium bicarbonate (many brand names), oil sprays, and antitranspirants. Copper is the most hazardous of these. However, it is a wide-spectrum fungicide that will control or help control most rose diseases.

If you garden in a Pacific coastal climate, powdery mildew is the most prevalent disease, and the best tactic is to avoid planting highly susceptible varieties. However, mildew infection can be killed by sprays or prevented by regular use of sprays.

Mildew spores are airborne and germinate most readily at temperatures of 55-65 with humidity near 100% but no rain. Generally, fog indicates prime conditions.

I take issue with the statement that PM is the most prevalent disease in Pacific coastal climates. PM is uncommon here in western Washington. Blackspot is king.

PM on phlox and bee balm is not the same as PM on roses. It won't travel from one to the other.

Have you tried the Cornell formula, baking soda and hort oil? I don't have the exact recipe but you can find that pretty easily. It doesn't work on blackspot, but it's supposed to be good for PM. I have had good results using it on indoor citrus to control scale and botrytis.

He was probably referring to the Pacific southwest. PM is definitely king here, in coastal southern California, and we rarely see any blackspot. And Cornell formula is completely worthless here, too, as are some of the stronger non-organics, like Banner Maxx. Really the only things that work are lime sulpher, copper and Compass here, with Compass being the only one that doesn't spot up the leaves almost as much as the mildew does.

So . . . it just depends.

Kathy

After defoliating a few too many roses with the supposed "Cornel" formual for PM posted on this forum and elsewhere many years ago, I purchased a product called "Remedy". It is a "baking soda" based product. For roses that have low/ to mildly moderate susceptibility to PM in my climate it worked without any side effects (such as defoliation). It required religious weekly sprayings until the conditions for P.M were gone and is not systemic, so heavy rain can wash it off. Roses that were very susceptible to P.M still succumbed dispite this regimen...Banner Maxx is more effective against B.S. with tests showing only marginal protection against P.M. One of the most readily available non-organic protections against PM that works is Ortho's Rose Pride which contains the active ingredient Triforene (it also works against B.S.)...If being organic is the most important feature to you about a rose, then try and find roses that are not susceptible or only mildly so.

Here is a link that might be useful: Remedy

Kathy,

I don't spray as much as I used to (maybe 2-3 times per year), but when I did I used a mix of mancozeb and propiconazole (ingredient in Banner Maxx) with much success. The leaves were always pristine as long as I sprayed every 7-10 days.

The mancozeb was for black spot, anthracnose, and botrytis. The propiconazole was for powdery mildew and rust. I never tried Compass (too expensive), but I am surprised you would say that Banner Maxx is worthless here in Southern California. I am inland about 20 miles, however.