These kill only the fungus spores and not beneficial insects, like ladybugs. And, they don't harm you, your kids or your pets. Ultrafine oil by Sunspray is a great oil to spray on your roses in early spring. Chemical or nonorganic fungicides do the job of killing off fungus spores, but can also harm you if you don't wear a respirator, goggles and protective clothing. If you choose to use these types of fungicides, be sure to alternate between two different kinds to reduce the chance of building up fungicide resistance in your garden.
Horticultural oils work by smothering the fungus or pest.
Be careful when using dormant oils because they are heavier and can cause damage to sensitive new growth. Don't apply these oils to roses that have swelling buds. It's better to use light oils that can be applied during the growing season. Sunspray ultrafine horticultural oil works great. You can usually find this at your local garden center.