Using Milk to Control Powdery Mildew - Garden Pest Tip

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.

In his experiments with zucchini plants, Bettiol found that a weekly spray of milk at a concentration of at least 10% (1 part milk to 9 parts water) significantly reduced the severity of powdery mildew infection on the plants by 90%. While some gardeners may be tempted to increase the concentration of milk for more control, Bettiol found that once concentrations rose above 30%, an innoccuous fungus began to grow on the plants. How does milk control powdery mildew?