article-Got powdery mildew-get milk

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Got Mildew? Get Milk!

By: Arzeena Hamir

Less than 3 years ago, researchers in South America discovered a new alternative to controlling powdery mildew. Wagner Bettiol, a scientist from Brazil, found that weekly sprays of milk controlled powdery mildew in zucchini just as effectively as synthetic fungicides such as fenarimol or benomyl. Not only was milk found to be effective at controlling the disease, it also acted as a foliar fertilizer, boosting the plant's immune system.

Powdery mildew in the cucurbit family is caused by the organism Sphaerotheca fuliginea. It is a serious disease that occurs worldwide. For decades, organic gardeners had to rely on making a spray from baking soda to control the disease. Now, instead of measuring out the baking soda and combining it with a surfactant (a "sticking" substance) of either oil or soap, gardeners need only head for their refrigerators.

How does milk control powdery mildew?

Scientist aren't 100% sure how milk works to control this disease. It seems that milk is a natural germicide. In addition, it contains several naturally occurring salts and amino acids that are taken up by the plant. From previous experiments using sodium bicarbonate, potassium phosphate, and other salts, researchers have found that the disease is sensitive to these salts. It is possible then, that milk boosts the plant's immune system to prevent the disease.

Milk used around the world

The benefits of using milk to control powdery mildew haven't been isolated to Brazil. Melon growers in New Zealand are saving thousands of dollars every year by spraying their crops with milk instead of synthetic fungicides. The melon growers in New Zealand have been so successful that the wine industry is taking notice and beginning experiments using milk to control powdery mildew in grapes.

What kind of milk should be used?

In Bettiol's original experiment, fresh milk was used, straight from the cow. However, this is obviously not feasible to most home gardeners. The research work in New Zealand actually found that using skim milk was just as effective. Not only was it cheaper, but the fact that the milk had no fat content meant that there was less chance of any odors.

Wagner Bettiol's original article was published in the journal Crop Science (Vol. 18, 1999, pp. 489-92). It can be found on-line at:
http://147.46.94.112/journal/sej/full/c12_199908_180801.pdf

Here is a recipe...

Mix 1 cup of milk with 9 cups of water.

Put the solution in a sprayer and spray the entire plant including the undersides of the leaves.

Do this twice a week and your powdery mildew problem should disappear.

Milk works in two ways: It has a germicidal effect--it kills the fungal spores-- and it also appears to stimulate plants in such a way that they become more resistant to the disease. In recent university tests, the milk and water spray was found to be more effective than the two most popular synthetic fungicides on the market today.