Thanks for writing. Do you know what's eating the leaves on your gerbera daisies? If it's an animal such as a deer or rabbit, it's best to look for a deer/rabbit repellent spray at your local garden center. If it's an insect, then you may need to treat for that particular bug. Without knowing which pest it is, though, I'm afraid I can't really recommend a specific product.
There are a number of fungicides that can be effective at stopping black spot disease from affecting your roses; look for them at your local garden center. And get more information on fighting black spot here: http://www.bhg.com/gardening/flowers/roses/how-to-save-roses-from-black-spot/
---Justin, Senior Garden Editor, BHG.com"