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.
Planting disease-resistant foliage, properly spacing plants for optimal air circulation, and watering in the morning are good practices to help reduce the incidence of powdery mildew. But when it arrives on plants, powdery mildew is a fast-spreading problem. So you must promptly remove diseased foliage if you want to control it.
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. 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.
Equipment / Tools
- Spray bottle or garden sprayer
Fill a Spray Bottle
Most experts advise using a mixture with a 40/60 ratio of milk to water. But you might want to experiment with different solution ratios to judge their effectiveness. Mix the milk solution in an ordinary pump spray bottle. For large applications, you can put the solution into a garden sprayer.
Spray the Plants
Spray the milk solution onto the plants, lightly coating all surfaces. Some experts advise spraying the plants in bright sunlight because it's believed that interaction with sunlight is what gives the solution its antifungal properties. Moreover, this treatment is often most successful as a preventive measure. So don't hesitate to spray any plants near your diseased foliage to keep them from developing powdery mildew.
Reapply the milk treatment every 10 to 14 days. With regular treatment, unaffected plants should remain free of powdery mildew and affected plants should improve. It's advised to continue spraying until conditions are no longer warm and humid, even if you don't see any more powdery mildew.
Tips for Using Milk Spray to Control Powdery Mildew
Various fungi cause powdery mildew, and milk solution is more effective on some than others. Certain types of plants also seem to respond well to the milk solution. They include:
Some gardeners feel the milk solution develops an unpleasant odor as it sours on plants, but this effect generally vanishes quickly. Besides, the odor of the milk is really no more unpleasant than that of commercial fungicides. And the solution is safer to use than many chemicals.
Keeping Ahead of Powdery Mildew. University of Vermont Website