How to Control Powdery Mildew With a Homemade Spray
How to Control Powdery Mildew With a Homemade Spray
If you are seeing powdery-looking patches on the foliage of your plants, you most likely have a case of the very common powdery mildew fungal disease.1 While there are chemical remedies for powdery mildew, few home gardeners need to use them; these controls are usually reserved for commercial farming operations. A better solution for home gardeners is simply to follow good cultural practices and, if desired, to apply a simple homemade powdery mildew spray.
You can apply a homemade spray to control the spread of the powdery mildew fungus. It won’t get rid of the fungus on leaves that already have it, but it can help prevent it from spreading to the rest of the plant.
What Is Powdery Mildew?
Powdery mildew is a fungal disease caused by many different species of fungi, although the most common in cucurbits is Podosphaera xanthii. It presents in a white powdery growth on the stems and leaves of plants.2
Signs of Powdery Mildew on Your Plant
- White or gray powdery spots on the leaves, stems, flowers, and even fruit of plants.1
- Curled, twisted, withered, or yellow leaves.
- Stunted growth of the plant.
- Changes in the flavor of fruit.
- Often appears in late spring and early summer during warm and dry conditions with high humidity.
What You’ll Need
Equipment / Tools
- Gallon container or empty milk jug
- Spray bottle or garden sprayer
Materials
- Baking soda
- Liquid non-detergent dishwashing soap
Instructions
Mix the Solution
In a gallon container or a clean milk jug, blend 1 gallon of water, 1 tablespoon of baking soda, and 1/2 teaspoon of liquid non-detergent dishwashing soap.
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Decant the Mixture
Pour some of the mixture into a spray bottle. You can also mix and spray directly from a pressure sprayer if desired.
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Spray the Plants
Spray your plants weekly, preferably on overcast days to prevent the mixture from burning the foliage. Coat all sides of the leaves and stems, and let them dry. Reapply the mixture after rain.
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Tips for Preventing Powdery Mildew
Good practices go a long way toward preventing or minimizing powdery mildew formation in the first place.
- Choose plants that are less susceptible to powdery mildew. Look for seeds or plants that are advertised as being resistant to powdery mildew. Hollyhocks and phlox, for example, are two ornamental plants that may be available in cultivars that are resistant to powdery mildew.
- Plant varieties that are known to be susceptible to powdery mildew with ample space between them for good airflow. The more space you have between plants, the better the air circulation and the less likely powdery mildew will spread. Similarly, dense bushy plants such as lilac (known to be susceptible to powdery mildew) can be thinned out to improve air circulation and minimize powdery mildew problems.
- Dispose of diseased leaves and plant stems by putting them in the trash or leaving them for the municipal compost pickup. Do not compost this material in your own compost pile, because the fungi spores can live on for quite a long time.
- Protect your plants during the winter. Spores of powdery mildew spread by wind and can survive the winter in plant debris or compost piles. Do not allow dead plant material to overwinter in the garden, because it will immediately infect young plants when they grow in the spring.
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What is the best treatment for powdery mildew?
The best treatment for powdery mildew is to use baking soda to kill the spores. You can also use potassium bicarbonate, which also kills the mold quickly.
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Is vinegar or baking soda better for powdery mildew?
Vinegar can work as a fungicide because the acetic acid in the vinegar changes the fungus’s pH, which will kill the disease. However, baking soda is more organic and safer to combine with other ingredients.
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Is Dawn dish soap good for powdery mildew?
Yes, Dawn dish soap and other soap sprays can be used on powdery mildew in the right concentration to avoid overwatering the plant. However, they are not as strong as other ingredients.
