Question
hi, i live 30 miles south of atlanta. my roses do very well apart from black spot when it is humid. i treat my roses every
3-4 weeks with a fungicide. my question is have you found any type of food or mineral to help prevent this devastating disease.  thanks, pam

Answer
You can only keep black spot disease under control, not cure it. Here is the reason. The black spot fungal spores float around in the air and when there is wind or rain, they are knocked to the ground. If they land on a rose leaf then they start their life cycle. If there was only one type of black spot disease then it would be easier to either bred roses that are immune or find a chemical that cures it. But there are at least eight strains and one year it may be a nasty one and the next not so bad. Some roses may be prone to a certain strain of this disease while others are not. Colours such as scarlets and orange reds are very prone and to a lesser  degree so are mauves and yellows. If you start with a healthy rose bought from a nursery that specializes in roses, get it off to a good start with water and fertilizer, there is a good chance that it will do much better in coping with black spot. Some roses are disease resistant and this means that they can drop 60% of their leaves and it will not effect their general health and vigour. If you live in certain States, then your weather may be far more prone to growing this disease. The best they have found so far to keep it at bay is to use a sulphur and dormant oil spray in the late fall and again in the early spring. Just follow the directions on the package for roses not the trees.