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.

Symptoms can also be observed on the underside of the leaves.

In severe cases of powdery mildew developing leaves may become distorted.

The disease affects flower buds. The disease is favored under warm days and cool nights with and high relative humidity.