Three-foot spacing is adequate for roses planted in a row with access on both sides. Finally, mulch well. This will inhibit weeds, slow evaporation of water, and moderate soil temperatures. Pest and Disease Control Old fashioned and floribunda roses tend to be more disease and pest-free. Other types of roses require regular attention to control disease and pest problems.
Black spot is a fungal leaf spot.
Affected leaves become spotted then yellow and fall off. Spray preventively with Funginex, or Dithane M-45. It's a good idea to alternate these fungicides every few months. Powdery mildew is especially prevalent with poor air circulation, cool nights and damp weather. Affected leaves and twigs may be removed, or controlled with Funginex.