Powdery mildew infections favor warm days and cool nights with and high relative humidity. Therefore, the disease typically develops in late spring and fall

Powdery mildew infections often first develop on the lower foliage and suckers at the base of the plant. Small, white powdery patches of mycelia and spores develop on leaves. These patches may coalesce and cover entire leaves, new shoots and flower buds

In severe cases of powdery mildew developing leaves, shoots and flower buds may become distorted