I feel certain it would work jst fine, but who would want to pay for the cost of using such a relatively nonspecific biocide? And since there is no scientific research available for hydrogen peroxide and roses, how would you know the minimum and optimum concentrations to use?

Hydrogen peroxide fungicides for home gardeners will be coming on the market soon. Zero-Tol is one brand. Here is an interesting article on the subject that mentions other new and environmentally friendly solutions for fungus diseases.
QC

Here is a link that might be useful: New Fungicides

Thanks QuiteContrary, that is good info to have. Very interesting article! (Hope they come out soon) I used corn meal a few days ago and that really seems to be helping!! No spread & spots are not getting bigger.

Got to checking into the hydrogen peroxide. Apparently it is corrosive and mutagenic. I don't know how safe it would really be, despite the manufacturer's claims. In Florida, we can grow many roses that aren't susceptible to diseases. That's the easiest way to deal with it! Plain liquid sulfur (e.g. Safer's garden fungicide) and Wilt-Pruf are other virtually nontoxic controls for blackspot.
Cheers,
QC

Here is a link that might be useful: Hydrogen Peroxide

QC, that is even better to know!
My main problem is that I have several HT & Austins that I "inherited" from my DH's late grandmother. At this point, I won't even purchase a HT for myself, and I'd REALLY have to think about an Austin (I'd said NO then I saw these bloom.) She did spray, and I will spray, every day if I have to, just nothing that will hurt my 2 year old or 2 dogs/cats.

As for purchasing roses that are disease resistant, that's all I will buy b/c of my feelings on spraying (besides, it makes life a little easier)

Thanks for the help (I need as much as I can get)
Mama :)

I have come across a remedy for blackspot which uses 5 tblsp each of Hydrogen peroxide and Baking Soda in a gallon of water. (see link) My parents have used it with success and I was keen to try it....until reading Quite Contrary's comments and link above!

Does this fact sheet pertain to the common household strength? Or is it relevant mostly to undiluted concentrations used in industry? Although at what strength does is a mutagen no longer a concern I'd like to know!

Check out the thread on vinegar as a remedy for blackspot too, wonderfully cheap and innocuous!

Here is a link that might be useful: Natural fungal controls

In the HP link: "health effects are unlikely to occur with commercial solutions of Hydrogen Peroxide used as a disinfectant."

So Ellymay I am not too worried. The caution seems designed for people who are handling pure HP in factories. I've been putting the diluted kind on my cuts since childhood, and I've only mutated very slightly :::-)

I'd take a good folk remedy over some new pesticide any day of the week - the devil you know, don'tcha know.

On another list they are claiming good results with corn flour spread on the ground early in the season.

How is HP going to do all of the things that I keep seeing on this forum. It is only water with an extra oxygen atom on each molecule. It does not kill germs or bacteria. The effect it has on a human wound is to release the extra oxygen molecule and bubble dirt and foriegn objects from the wound. I am unsure of what the proported effect would be on any organism and would love to know the causitive effects.

See:

http://forums2.gardenweb.com/forums/load/roses/msg0620204532371.html?6

Here is a link that might be useful: How does H2O2 work?