Anything that's appropriate for diseases on ornamentals will work--there are a ton of things out there--check the gardening section at Lowe's or boxstore. Ortho comes to mind immediately (Orthonex, Daconil), but there are many other manufacturers. Floofy uses Cleary's (sp?) in Florida and has had good results. It's also a good idea to alternate between things that use different active ingredients--that helps keep anything that seems to persist from developing an "immunity" against the ingredient in just one product. Systemics seem to work particularly well for a lot of people. These get absorbed into the plant's tissues and do their job from the inside out. Their effects also seem to last longer than sprays that just remain on the plant's surfaces. There's also a product out called "Spreader-Sticker" which, when mixed with what you're spraying with, will coat the plant more evenly and help keep the disease control from washing off when you water. The downside is, it leaves a pale blue residue on the plants that's really hard to remove, but most people would much rather live with that than have to deal with repeated and more frequent spraying....