Powdery mildew affects zucchini and other squash.
Mildew is a common problem in vegetable gardens. It is caused by the Sphaerotheca fuliginea organism, a disease that occurs worldwide and is often treated in commercial agriculture production with toxic synthetic fungicides such as fenarimol or benomyl. Legal organic growing standards and practices require the use of fungicides derived from all-natural sources. Milk has long been a home remedy for powdery mildew and it is now used in large-scale commercial organic vegetable farms. Does this Spark an idea?
Symptoms
Powdery mildew appears as a dusty white or gray coating over leaf surfaces and other plant parts. It is spread by spores. The mildew begins as small circular white spots that expand and coalesce to produce a continuous mat of powdery covering. Symptoms occur late in the growing cycle, often under conditions of high humidity or crowding. The fungus causes nutrient loss, yellowing and shriveled leaves, plant tissue death and crop loss.
Research
Wagner Bettiol of the environmental laboratory of Embrapa, the Brazilian Agricultural Research Corporation, published research in "Crop Science" journal showing milk to be an effective deterrent for powdery mildew on vegetable plants. A one-part milk and nine-parts water spray solution used twice weekly on zucchini plants was found to reduce mildew disease by 90 percent. Increased concentrations of milk were found to produce an additional undesirable fungus.
Commercial Use
Other powdery mildew fungicides used commercially in organic production include cinnamon oil, neem oil and a hydrogen dioxide solution. Biological fungicides such as AQ10 and Serenade make use of fungi that are parasitic to the powdery mildew fungi. A yeast-like fungus (Pseudozyma flocculosa) has been tested for use against powdery mildew with promising results, according to the University of Florida Extension website. All biological control products require high humidity to be effective.
Home Use
Milk is a natural germicide. It contains several salts and amino acids that are thought to be the effective agents against mildew fungi. Skim milk is as effective as whole milk when used as a spray. It is less expensive and has less odor-producing fats. Milk solutions are used in simple plastic hand-held sprayers or in commercial home-use sprayers. It is sprayed on the upper side and underside of plants weekly as leaves begin to develop.
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