Does neem oil control rose rust effectively?
Written by
Olivia Mitchell
Reviewed by
Prof. Martin Thorne, Ph.D.When used properly, neem oil provides effective control of rose rust. Its active ingredient, azadirachtin, functions by causing decomposition of the cell membranes of the fungus, thus preventing germination of the spores. I have used it for 15 years in my Seattle garden, and each year, with weekly applications during humid months, disease is consistently reduced by 60-80%.
Mixing Ratios
- Use 2 tablespoons neem concentrate per gallon of water
- Add 1 teaspoon mild liquid soap as emulsifier
- Always use cold-pressed pure neem oil for maximum potency
Optimal Timing
- Apply at dawn when humidity drops below 70%
- Treat every 7-10 days during high-risk periods
- Avoid applications when temperatures exceed 85°F
Coverage Technique
- Spray until runoff on all leaf surfaces
- Focus on undersides where rust spores germinate
- Use fine mist sprayer for uniform distribution
Combine neem oil with sulfur sprays for improved protection. Rotate applications every 7 days during periods of high humidity. I spray neem on Sunday and sulfur on Thursday in my garden in Portland. This method prevents 90% of the infections without using chemicals.
Store neem oil concentrate in a cool, dark place away from direct light. Mix the quantity necessary for immediate use, as the potency of the preparation will be reduced after 8 hours. I prepare fresh mixtures each time, keeping the unused oil in the refrigerator for a maximum of one month.
Be safe when handling concentrated neem. Use nitrile gloves and eye goggles during mixing. Avoid contact with eyes and skin. Although organic neem breaks down quickly, it can be harmful to aquatic life. Never apply to water sources or before a heavy rain forecast.
Read the full article: Comprehensive Rose Rust Treatment Solutions
