Cucurbits Downy mildew and powdery mildew are diseases that may look similar at first glance, but are actually very different. Both usually affect only the leaves. Downy mildew can be identified from the fungal layer on the underside of leaf, in moist weather, accompanied by leaf spots on the top of the leaf.
Powdery mildew causes white, powdery, fungal growth in the absence of any leaf spotting.
This growth is on both sides of the leaves, and is present at all times. Downy mildew is a fungal disease caused by Pseudoperonospora cubensis . The disease is found worldwide in temperate and tropical areas and is one of the most important foliar diseases of cucurbits. It occurs sporadically in the northeast. It causes small fruit, due to lost leaf area, and the fruit may have a poor flavor.