It must be applied weekly. Sulfur and lime can be effective against black spot, powdery mildew, and rust. They create a thin coating that can prevent spores from fungal diseases from invading the leaves. Treatment is begun when new leaves appear in spring and must be repeated whenever you see new growth. Repeat treatment every 7 to 14 days.
Neem oil can be toxic to bees, so it is safest to spray it in the evening.
Inspect plants on a regular basis so that you can detect any diseases or pests before they become a problem. Become familiar with the pests and diseases that are common in your area. Before you treat plants for pest problems, look for beneficial insects that are the natural enemies of rose pests. Often found in clusters on new shoots and flower buds, especially on over-fertilized plants. May cause leaves to discolor or turn black with sooty mold.