I’m just glad you are getting rain. Could it be that if water was plentiful when the roses are building their buds that the petals would be pink? The drought could cause them to be white, maybe that takes less water?
Whitewash , or ' real mildew ', is equally feared with roses. The deterioration image is a messy, white pollinated appearance on the various parts of the plant and therefore easily recognizable for every garden lover. All green parts of the rose bush are affected: leaves, non-wooded shoots, including the petals. The first visible symptoms are the slightly raised red-colored zones on the rose leaf. Shortly thereafter the white fungal threads appear.
An infection is mainly to be expected in dry conditions, although a small amount of moisture (eg dew) is still required for spore germination. The fungus tolerates very poor water over longer periods and the spores that come in contact with it often die. Whitewash is therefore to be expected mainly on warm, sunny days, but with slightly dewy morning.
@pyrrhula Thanks for all that info Ferry, they don't seem to have much of what you describe. When we had our drought, they were still white. They only turned pinkish after some rain ;-)
An infection is mainly to be expected in dry conditions, although a small amount of moisture (eg dew) is still required for spore germination. The fungus tolerates very poor water over longer periods and the spores that come in contact with it often die. Whitewash is therefore to be expected mainly on warm, sunny days, but with slightly dewy morning.