OUTDOOR EXPERIMENTS for control of powdery mildew of rose, resulting from infection by Sphaerotheca pannosa, were conducted at Livermore in 1969. Twelve plants of the variety “Forever Yours” were used per treatment, and each treatment was replicated three times. The roses were sprayed once every two weeks (with two exceptions when the intervals were three weeks) from July 23 until November 24 and 25 when results were recorded. All treatments were applied as sprays and all of the foliage was treated to the point of run-off. Triton B1956 spreader-sticker was added to each spray treatment at the rate of 1.2 ml (¼ tsp) per gallon.