Powdery Mildew - The White Menace
The leaves of a deciduous azalea should be a deep red, not white.
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powdery mildew has turned the deep burgundy leaves of this Crimson King maple white.
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Warm days, cool humid nights, dry soil and morning shade, promotes this prevalent disease. When conditions are right, powdery mildew spores are carried in the wind and rain. A white powdery substance first appears on the new growth. It coats the leaves, blossoms, buds and eventually the entire plant. Affected parts quickly yellow and become distorted.
New leaves and flowers are affected first.
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An infected rose leaf shows typical signs of the disease: a white powder and distortion.
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Cause: When selecting plants, look for varieties that are resistant to powdery mildew. Provide susceptible plants with morning sun so dew quickly evaporates. Rain and cool nights followed by humid days, overhead watering, fog and dry soil also encourages this prevalent disease.
Prevention: Wet foliage and dry soil encourages this fungus so water before soil it becomes too dry. When watering, avoid getting foliage wet and don't water late in the day. Don’t crowd plants as good air circulation deters the fungal spores from settling.
In Fall: To reduce the spread of powdery mildew, remove all the infected foliage and flowers from soil and on the plant. To kill remaining spores on the plant and the soil, spray with either baking soda or milk. Both are organic, non-toxic and they work. The recipes are below.
Prevention: Wet foliage and dry soil encourages this fungus so water before soil it becomes too dry. When watering, avoid getting foliage wet and don't water late in the day. Don’t crowd plants as good air circulation deters the fungal spores from settling.
In Fall: To reduce the spread of powdery mildew, remove all the infected foliage and flowers from soil and on the plant. To kill remaining spores on the plant and the soil, spray with either baking soda or milk. Both are organic, non-toxic and they work. The recipes are below.
Powdery mildew affects all plant parts including stems, flowers and leaves as noted on this speedwell.
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The beginnings of powdery mildew on a catalpa leaf.
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Control: Since the disease overwinters, remove infected plant parts including infected fallen leaves. Apply organic mulch and water often to reduce water stress. Infected tissues will not recover but applying a fungicide will reduce the spread of the disease.
Apply sulfur or copper according to the manufacturers instructions, every 7 to 10 days. Effective non chemical controls include baking soda or milk. Whatever you use, apply to all areas of the plant thoroughly including the ground, but don’t apply in full sun to prevent tissue damage.
Note that the infected foliage, buds and stems will not recover with any fungicide as the plant tissues are damaged. The fungicides stop the spread of the disease to other parts of the plant. It you want to remove infected plant parts, do so. Fiinish up by spraying the remaining plant and soil with a fungicide.
Apply sulfur or copper according to the manufacturers instructions, every 7 to 10 days. Effective non chemical controls include baking soda or milk. Whatever you use, apply to all areas of the plant thoroughly including the ground, but don’t apply in full sun to prevent tissue damage.
Note that the infected foliage, buds and stems will not recover with any fungicide as the plant tissues are damaged. The fungicides stop the spread of the disease to other parts of the plant. It you want to remove infected plant parts, do so. Fiinish up by spraying the remaining plant and soil with a fungicide.
A zucchini leaf.
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Homemade Solutions
Baking Soda To prevent and to control powdery mildew, spray susceptible plants weekly. 1 tablespoon baking soda ¼ teaspoon of liquid dishwashing soap ½ teaspoon of vegetable oil 1 gallon of water Milk Spray 1 part milk to 2 to 3 parts of water apply every 10 to 14 days |
Members of the cucumber family are susceptible to powdery mildew as this zucchini plants shows.
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Garden phlox are very prone to powdery mildew.
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A tuberous begonia.
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This tomato has succumbed to powdery mildew late in the season due to foggy mornings.
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