Holly...
As far as I know Safer spray is an insecticide, not a fungicide, so unless they have a product that i don't know about I doubt it would do any good. Even though it is totally safe for your pets. Most fungicides have a danger rating to them for one reason only, that they are an eye irritant, and cause blindness in its straight form. I would check with your vet and ask him his opinion. Once sprayed, and dried I think it should be safe because I seriously doubt the dog will try to eat a
rose bush or even rub his face in it.
The only other thing that I can think of that may help is not to water the
plant over the leaves in the sunshine and let a liquid fert touch the leaves. A properly fertilized
plant can withstand disease attacks and sometimes not even get them.