This is a Environmental friendly solution, it may help,
Baking Soda Spray:
1 tbsp vegetable oil
1 gallon unchlorinated water
1 tbsp apple cider vinegar
1 tsp Listerine (yes, the famous mouthwash, not mint flavour, just regular)
1 tbsp liquid soap
1 ½ tbsp baking soda
Pump sprayer (large)
Mix the baking soda, soap, Listerine, and oil with 1 cup water. Add the vinegar last so that the mix won’t bubble over. Pour the mixture into the sprayer and add 1 gallon water. Shake to combine. Spray plants thoroughly.
This formulation may need to be reapplied after rain since it tends to wash off. One side benefit to the baking soda spray is that insects don’t love it either!
Some folks have had certain success with stinging nettle spray. It is meant to help plants resist mildew and other diseases such as blackspot and rust. To make: gather 1 pound of stinging nettle plants (use long rubber gloves and wear protective clothing to prevent from being stung!); crush stinging nettle leaves and put into an old burlap sack or pillow case. Submerge the bag in a one-gallon bucket containing unchlorinated water, cover and let sit in a warm place for a week. Strain mixture through cheesecloth or mesh. Dilute liquid stinging nettle concentrate with 5 parts water to 1 part concentrate. Spray this over rose bushes every two weeks.
