Rose Rust Control

Ideal Conditions for Infection

• Cool, moist weather, typically around 64 to 69 degrees Fahrenheit, provides prime conditions for rose rust to develop. Rainy, foggy or misty conditions are often when rose rust will form because leaves remain consistently wet for four hours or more. The rust spores reproduce every 10 to 14 days during summer months. If infected leaves are left on the ground, the rust spores are easily spread to other plants by wind, rain and even insects.

Signs of Rose Rust

• Rose rust is a fungal disease that appears as raised reddish-orange spots on the undersides of leaves and yellow spots on the surface. Long streaks may also appear on the rose stems. If left untreated, these spots develop into rust warts that turn black during the fall, causing defoliation of the entire plant

Treatment and Control

• Remove infected leaves and stems as soon as you see rust spots develop. Gather leaves that have fallen on the ground and either burn or bag them up. Don't add infected leaves to compost because the rust will return when the recycled material is put back into the soil. Spray roses with wettable sulphur or fungicidal soap on days when the temperature is below 80 degrees Fahrenheit. Spraying wettable sulphur on warmer days will damage your plants.

Prevention

• To prevent rose rust and other fungal diseases like mildew, avoid over-watering your roses. Soaked soil is an ideal environment for fungus to grow. Add organic matter such as compost and plant roses in raised beds to prevent rose rust from forming. Don't work in a wet garden; it increases the risk of spreading fungus spores to other plants. Avoid watering the plant's foliage directly and ensure plants are spaced far enough apart for adequate aeration. Plant small rosebushes about 3 feet apart and larger bushes 4 feet apart. Each fall, clean away debris from the ground to prevent rust spores from affecting new plants in spring.