A disease on the foliage of roses. It is caused by moisture. To avoid, plant disease - resistant roses. Clean up after pruning. One can use fungicide during damp weather - captan, copper, or lime sulphur are most effective when you follow the instructions carefully. One can also use baking soda (sodium bicarbonate) at a rate of one teaspoon to one gallon. Use in the morning to prevent sun scald. One can also try neem oil.