Symptoms:
Powdery mildew is first noticed on older leaves as a yellow spotted appearance, that upon closer inspection has a whitish-gray powder on the surface. The leaves will eventually die, but usually remain attached to the stem. The disease is worse under warm, dry conditions.

Control:
Sulfur dusts or wettable sulfur sprays are effective preventative controls. The established disease will require one of the labelled mildew fungicides.