Squash, zucchini, cucumber and other garden plants often come under attack by powdery mildew, which disfigures and weakens the plant. Powdery mildew can be identified by a dusty white or tan coating, and curling or twisting leaves. Spray a weak solution of milk and water on your squash and other plants to combat powdery mildew in a natural, organic matter. Cow's milk has germicidal properties, fertilizes the soil and provides nutrition to your squash and other plants.
Create a solution of one part milk to three-to-nine parts water. Higher concentrations of milk will fight powdery mildew more effectively, but may also cause mold to form on your squash plants. Consider using skim milk, which contains no fat and won't go rancid and produce odors as it dries on the plant.
Transfer your milk-and-water solution into a sprayer or misting bottle.
Spay the leaves of your squash and any other plants infected with powdery mildew with the milk-and-water solution. Do not drench them; a light coating on the tops and bottoms of the leaves will suffice.
Store any leftover milk-and-water solution in the refrigerator for up to one week, or use the solution to water your garden plants.
Repeat applications of the milk-and-water solution once or twice a week for as long as necessary to fight powdery mildew on your squash plants.