What it is
So what is powdery mildew anyway? This fungus is a type of mildew that is marked by a white floury covering consisting of spores on both sides of a plant’s leaves. It is one of the most widespread fungal diseases and no plant is completely immune to the disease. This type of fungus is host specific, meaning if you find it on one type of plant, it doesn’t mean it will spread to your other plants. For example, if you have powdery mildew on your roses, it won’t spread to your lilacs. While the spores can move from a specific type of plant to the same type of plant by wind, they can also spread by direct contact through insects, animals and gardeners.
What to Look For
Powdery mildew is most happy when plant leaves are dry, the lighting is low, temperatures are warm and humidity is high. Ideal conditions for powdery mildew growth is often during the late spring or early summer when evenings are still cool, but the days are beginning to get warm. At first the powdery mildew looks like dust and may be able to be brushed off with your hand, but it comes back and appears as light white or gray spots on the tops and bottoms of the leaves, stems, flowers and even fruit or vegetables.
How to control the Fungus
These remedies have been proven effective, but just like all diseases, they can build up a resistance to remedies. So we recommend spraying for powdery mildew every week (or recommended amount per remedy), but alternate between remedies as there are 8 recipes to choose from.
- Milk: Mix one-part milk to two parts water; spray once a week.
- Baking Soda: 1 tablespoon baking soda, 2 tablespoons ultra fine canola oil, 1 gallon of water. Combine all ingredients and shake well; spray once a week.
- Garlic: Blend two bulbs (not cloves) of fresh garlic in a quart of water with a few drops of liquid soap. The creation should be strained through cheesecloth or other sort of strainer to remove solids and then refrigerated. That concentrate should then be diluted 1:10 with water before spraying the plants once a week.
- Compost Tea: Mix one part of finished compost with six parts of water and let it soak for a week, then strain and dilute with water until it’s the color of tea; spray once a week.
- Oil (vegetable seed, canola, mint, rosemary, sesame, fish): Any of these oils can be used, at a rate of 2.5 to 3 Tablespoons per gallon of water, with the addition of a quarter-teaspoon of liquid soap to emulsify the oil. Spray every 7-14 days.
- Mouthwash: Mix one-part generic, ethanol based mouthwash with three parts water and spray on plants once a week; make sure to not spray new budding plants as it will damage them.
- Vinegar: Mix 4 tbs of vinegar with 1 gallon of water. Reapply every three days.
- Water: As stated above, powdery mildew does not survive well in moist conditions, so spraying the plants in the later part of the day with water from your hose just might do the trick!
How to Prevent
- Make sure there is enough spacing between your plants
- It is harder for the spores to spread when the plant leaves are wet, so it is important to keep the moisture levels up. The mildew also loves the cool air so try and plant in a place that gets plenty of sunlight.
- Remove or treat all infested weeds and plants on your property and cut away infested twigs on fruit trees at the earliest signs of infestation Throw away the infected plants, do not compost!
- Maintain healthy plants. Stressed plants are often attacked first, so it is important to monitor and remove unhealthy plants.