Powdery mildew season has begun (May), so act now to prevent or slow the development of this disfiguring (though not usually lethal) disease. Research published in Crop Protection demonstrated good results for preventing and managing mildew by spraying once a week with a 20%-40% solution of non-fat milk diluted in water. The down side to this organic remedy is the white residue left behind by the milk, which resembles the mildew we’re trying to cure in the first place! Other less-toxic sprays that are new to the market are:
- Eco E-Rase (also sold as Detur), a jojoba oil spray that smothers mildew spores;
- Citrall Organic Lawn and Garden Fungicide derived from Backhousia citriodora (Lemon Myrtle), native to Australia;
- Rose Defense made with Neem oil, which is not so new, but is still unfamiliar to many gardeners.
Go online to Colorado State University for a fact sheet on powdery mildew.