To kill mildew on your rose bushes mix the following ingredients together: 1 tbsp of vegetable oil - 1 gallon of unchlorinated water - 1 tbsp of apple cider vinegar - 1 tsp of Listerine (regular, not mint) - 1 tbsp liquid soap - 1 1/2 tbsp baking soda. Mix the baking soda, soap, Listerine, and oil with one cup of water. Add the vinegar last so the mixture wont boil over. Pour the mixture into a sprayer and add the gallon of water. Shake the mixture well and spray liberally over the plant. Reapply after rains since it will wash off. One side benefit of this baking soda spray is that insects do not like it.