To water your roses properly is the best way that you will never need a powdery mildew treatment
Of course, it is not only watering that will avoid an infestation with powdery mildew but dry soil is definitively a trigger.
This fungal disease is often seen later in the season, and appears with whitish-grey powdery patches on leaves and younger stems. In severe cases, buds will fail to open.
Powdery mildew can appear on any type of rose, but tall roses with strong new growth throughout the growing season will be more troubled.
Left untreated, the disease could cover the whole plant.
As I mentioned before, the fungi grow properly in dry soil and on dry foliage.
Some gardeners recommend overhead watering in the morning. That would wash away the fungal spores from the foliage before they can establish themselves.
Anyway, I only do that on sunny, dry days to avoid other diseases, which grow well on wet foliage and buds.
For me, good air circulation around the flowers is one of the most effective ways to prevent powdery mildew.
That means planting the flowers in open areas is better than in a crowded environment.
Planting resistant varieties in a sunny place and pruning them regularly to get a good air circulation will do a good job to avoid the disease.
Do not forget to remove fallen leaves from the base and burn them.
Although you plant and grow your flower in the best-known way, it will not always be possible to avoid powdery mildew infestation.
The following treatment methods will help you to get rid of the ugly disease:
Of course, you can spray your plants with a chemical fungicide at the first sight of the disease. Good products to use are Bayer’s rose care products.