Brazilian scientist Wagner Bettiol was looking for a cheap way to control powdery mildew when he discovered that weekly sprays of milk controlled the growth of powdery mildew in zucchini just as effectively as toxic fungicides such as fenarimol or benomyl. And not only that, the milk spray boosted the plants' immune systems.
For decades, organic gardeners have been relying on a somewhat cumbersome spray of baking soda combined with a sticking agent?like oil or soap?to fight powdery mildew without poison. But Bettiol found that the super-easy concoction of nine parts water to one part milk slashed the severity of powdery mildew infection by 90 percent.
- Bettiol used raw milk straight from the cow, but other researchers have found store-bought skim milk to be equally effective.
- Don't be tempted to go for better, faster results by increasing the ratio of milk to water. Bettiol found that using solutions with more than 30 percent milk caused a harmless fungus to grow on the plants.