How to Apply Fungicide to Roses

If you’ve cultivated roses (Rose spp.) for any length of time, you probably have some familiarity with fungal diseases. Fungal diseases usually produce cottony growth, referred to as mycelium, or small bumps that look like a plant’s equivalent of acne, known as pustules. The most prolific fungal pests -- powdery mildew (Podosphaera pannosa var. rosae), black spot fungus (Diplocarpon rosae) and rust (Phragmidium mucronatum) – rear their fuzzy heads even if you follow good cultural practices, such as irrigating effectively and giving the roses room to breathe. Fortunately, the most effective fungicides are organic, and applying them is as simple as mixing and spraying -- after you identify the fungus, of course.

Spray bottle
Measuring spoon
All-purpose bleach
Distilled water
70 percent neem oil
Fungicide containing 90 percent sulfur powder
Fungicide containing 85 percent potassium bicarbonate

Instructions

- 1
  Check the foliage, sepals, buds, shoots and petals for a whitish-gray mycelium, a strong indication of powdery mildew fungus. Powdery mildew occasionally causes leaves to wilt and droop.
- 2
  Soak a spray bottle and measuring spoon in a mixture of 1 part bleach and 9 parts water for 15 minutes. Remove the bottle and spoon and allow them to air dry.
- 3
  Mix 1/2 tablespoon of 70 percent neem oil with 4 cups of distilled water in a spray bottle and spray all parts of the rose bush – sepals, foliage, shoots, buds and petals -- until completely wet on all sides, if you find powdery mildew fungus. Apply neem oil once a week until it eliminates powdery mildew fungus, and every two weeks to prevent powdery mildew fungus.
- 4
  Examine the tops of the rose leaves for bright yellow patches and the bottoms for reddish-brown blemishes, signs of rust fungus. Rust also causes premature leaf drop in some rose varieties.
- 5
  Mix together 1/2 tablespoon of fungicide containing 90 percent sulfur powder with 4 cups of distilled water in a spray bottle, and spray the leaves on both sides at the first sign of rust fungus. Apply sulfur every 5 to 10 days and after rainfall, until you eliminate rust fungus.
- 6
  Inspect the stems and the tops of the leaves for moderate-sized black spots with fibrous margins, classic symptoms of black spot fungus.
- 7
  Mix 1/2 tablespoon of a fungicide containing 85 percent potassium bicarbonate with 4 cups of distilled water in a spray bottle and spray the stems and both sides of the leaves at the first instance of black spot fungus. Apply potassium bicarbonate every week and after rainfall during the growing season to eliminate and control black spot.

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