Blooms are abundant now and how we enjoy their colors and fragrance. However, if you grow hybrid teas you may notice black feathery spots that spread and cause your rose leaves to turn yellow and fall off. This fungal disease is called black spot (Diplocarpon rosea). The most effective way to control this troublesome disease is to spray a systemic fungicide combined with a contact fungicide. Spray your roses every 14 days if you want to prevent this disease from weakening your roses.