JARS v63n4 - Tips for Beginners: The Cornell Powdery Mildew Cure

Tips for Beginners: The Cornell Powdery Mildew Cure
Frances Burns
Vida, Oregon
Modified from the Editor's Byte in the Eugene Chapter Newsletter, April 2009

Many thanks to the Siuslaw Chapter Newsletter and Shirley Wilson, a member of Siuslaw Chapter, for sharing a great source of gardening information. Shirley subscribes to a horticultural news service called "The Avant Gardener" (Thomas Powell, Editor and Publisher), and the following is an article on The Cornell Mildew Cure from it that Shirley would like to share.

Many rose growers are using a formula developed by Cornell University to control powdery mildew and black spot. This formula is also remarkably effective against the strain of mildew fungus that attacks crape myrtles ( Lagerstroemia spp.), reports Texas gardener Field Roebuck from Dallas, Texas. Mr. Roebuck, who uses the Cornell spray on his roses, states: "One evening, with spray solution remaining, I saw that our four, large, 30-year-old white crape myrtles were covered with mildew. So, instead of mixing up my usual lime-sulfur spray, I doused them with the remaining rose spray. The results were amazing. As I sprayed, the mildew dissolved into nothingness. And more importantly, it never came back. That one treatment did the job for the entire season and that has been the case every year since".

Here is the formula: Into four liters (one US gallon) of water, mix 30 cc (two tablespoons) of light horticultural oil (e.g., Sunspray oil), 18 cc (one heaping tablespoon) of baking soda and 15 cc (one tablespoon) of a mild liquid dish-washing detergent (e.g., Palmolive Green). Mix well and spray with a pump-up sprayer late in the evening when the sun is no longer on the foliage. Spray both sides of the leaves and all the wood to the point of runoff.

Frances Burns is a member of the Eugene Chapter and is Editor of its Newsletter.