How to Control Black Spot on Roses

Black spot is a fungus disease that appears as round, black spots on the leaves of rose plants. There may be a distinctive yellow band around the black spot and leaves may fall prematurely. Left untreated, black spot may infect young canes.

Difficulty:

Moderately challenging

Instructions

Things You'll Need

• Dormant Oil
• Bordeaux Mixture
• Leaf Rakes
• Plastic Bags
• Plastic bags
• 1 teaspoon baking soda

1. Look for black spot on the leaves of rose plants. This fungus disease will appear as round, black spots ringed by yellow tissue.

2. Water roses only from below. Try not to get the foliage wet when you water.

3. Water in the early morning hours so the rose plant has time to dry during the day.

4. Rake up any fallen leaves from the soil surrounding the plant. Black spot as well as other fungus diseases are transmitted by water splashing back up onto the leaves and stems.

5. Remove any diseased leaves. Pick off and destroy any foliage that has evidence of black spot. Dispose of infected foliage in a sealed plastic bag.

6. Dust roses infected with black spot with sulfur powder. Sulfur will not kill the fungus spores, but it will prevent a new generation from germinating.

7. Spray a solution of 1 tsp. baking soda mixed in 1 qt. warm water in the early morning hours.

8. Spray roses with a dormant oil or Bordeaux mixture when plants are dormant (usually in winter).

Tips & Warnings

• Black spot is very difficult to eliminate once it appears. Prevention is the best form of defense.

• Spray organic fungicides early in the day for best results.

• Chemical fungicides are also available for the control of black spot.

• Always use the least toxic method of pest control first.

• If you choose to use a chemical fungicide, always wear protective clothing and safety gear, including a long-sleeved shirt, long pants, neoprene gloves, goggles and a respirator.