If white, gray or brown spots appear on the leaves and plant parts of the zucchini, the plant is affected by powdery mildew or downy mildew. Both are fungal diseases and must be combated immediately as they can lead to the death of the leaves or the entire plant.
How to treat mildew on zucchini?
Zucchini powdery mildew is a fungal disease that causes white, gray or brown spots on leaves and plant parts. Affected parts should be removed immediately and treated with anti-fungal agents. New zucchini varieties such as “Diamant”, “Mastil F1” and “Leila F1” are resistant to powdery mildew.
Powdery mildew
With powdery mildew, white, mealy spots cover the surfaces of the leaves, but also stems and fruits. Eventually the leaves turn brown and die. The cause of powdery mildew is prolonged dryness.
Downy mildew
Cold, wet weather can lead to downy mildew infestation. You can recognize it by whitish to brownish, velvety coatings on the underside of the leaves and brown or yellow spots on the upper side.
Combat
- Immediately remove affected leaves and plant parts and dispose of them in the trash
- Injections with anti-fungal agents such as “Plant-Fungus-Free” from Detia (€11.00 on Amazon) or “Fungisan®Rose and Vegetable-Fungus-Free” from Neudorff
- Garlic or onion infusion against downy mildew
- Fresh milk-water mix in a ratio of 1:9, spray 2-3 times a week
Tips & Tricks
Many new zucchini varieties are resistant to powdery mildew. These include the varieties “Diamant”, “Mastil F1” and “Leila F1”.
