How to Use Milk Spray to Control Powdery Mildew

You can do everything right in your garden and still have problems, including powdery mildew. Powdery mildew refers to a group of fungal diseases that all show up as a powdery white coating on plants, especially when humidity is high. It usually doesn’t kill plants, but it can weaken them and lead to poor growth and yield. Keeping your plants healthy will help minimize damage, but sometimes you need the aid of a fungicide. However, that doesn’t mean you have to use chemicals. For powdery mildew, try a milk spray.

How Milk Spray Works as a Fungicide

There is ongoing research regarding using milk as an antifungal spray, specifically against powdery mildew on cucumbers and squash. But it’s still uncertain as to exactly how milk works against the fungus.

It appears the milk protein creates an antiseptic effect when exposed to sunlight, which is why you should apply the solution in bright sun. The protein is in the milk fat, though researchers have experimented with both whole and skim milk. You can try experiments for yourself with whatever you have on hand. For accurate testing, spray the solution on only some plants while leaving others untreated.

When to Use Milk Spray to Control Powdery Mildew

Milk works best as a preventative measure rather than as a cure. This means you ideally should apply it at the start of warm, humid weather before powdery mildew has appeared on your plants. Through experience, you might already know the times of year when the disease is likely to show up.

Spray your susceptible plants as soon as the prime mildew conditions are setting in or when foliage first begins to show signs of mildew.1 If your garden does better than it has in the past with powdery mildew, you can be fairly certain your treatment has had a positive effect.