The Ants are inconsequential, but the diseases need attention. Prevention of these two diseases is achieved by spraying with a preventative fungicide appropriate for Roses. You can purchase one of any number of brands of fungicide from your local nursery. If the problem is severe and persistent, there really is no other option than to treat the roses with a fungicide. (Needless to say, don't use these in proximity to any plot of ground that will be used for food production.)

Bayer also makes a fungicide and fertilizer combination drench that is simply watered into the soil at the base of the plants and it is absorbed into the plant through the roots. Most people find it very effective but it takes a couple of applications to build up sufficient chemical in the plant to affect disease control.

Lastly, if you object to the use of chemicals in your garden, (many people do, and for good reasons) then you need to find out which varieties of roses do well in your climate without chemical intervention. Selecting disease free varieties is often many people's first choice for dealing with disease problems.

Regards,
Paul

I agree with Paul. I live in Kansas where its not if I get black spot but when and that's because I love hybrid tea roses. However, if your noticing ants, you might want to check to see if the roses have aphids. You will have to check underneath the leaves, if you do then some soapy water will take care of them.

Some roses are more or less resistant to B.S. if u find some roses are heavily diseased with BS then spores from that bush will infect other nearby bushes, so the BEST thing is to give heavily infested bushes the good old SHOVEL PRUNE (get rid of the bush) I used to spray with chemicals, but eventually got tired of paying the chemical industry for the pleasure of poisoning the environment. For instance, most David Austin roses are highly disease resistant.

As for powdery mildew, cut back on nitrogen fertilizer. I used to fertilize like no tomorrow, get huge growth, but the growth is soft and very susceptible to mildew. After a while, I started fertilizing ONLY with ground up composted Christmas trees. The roses still smell just as good, just the bush is a little smaller, but IT IS DISEASE FREE!!! because I do not apply any commercial nitrogen.

Also the compost ground up Christmas trees (use whatever u can find) FEEDS the soil, and there is a very rich population of bacteria in there that EAT FUNGAL SPORES, such as the Black spot spores that fall on the ground. Usually rain will splash on the ground, and the spores then get splashed up on the leaves. If there is a good heavy (several inch) layer of compost, the spores are eaten by bacteria before they can cause trouble for the bush, and also THE TEXTURE of the compost STOPS RAIN FROM SPLASHING, but instead it soaks into the ground very nicely.

I have not had to spray for several years - I am sick and tired of spraying and wasting my money - MUCH better to do things the natural way.