Powdery mildew

Erysiphaceae

Powdery mildew is a fast-spreading fungal disease and one of the most common and recognisable to find in a garden but does not cause significant damage to plants. Unlike other fungal diseases, powdery mildew does not require moisture to infect a plant and is mostly associated with water stress of plants due to an unusually high water content in the spores of the fungi. There are several types of the powdery mildew fungi, but they all tend to look the same and they are host specific - powdery mildew on pumpkins won't spread to roses.
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Identification

Plants may look like they have been dusted with babypowder or flower. A white, dusty coating on leaves, stems and flowers will be visible - especially on the plant surface.

Growth factors

Poor air circulation, facilitated by low planting distance between plants. High humidity at night followed by low humidity during the day.

Symptoms

Older lesions turn brown and appeared shriveled
White 'powder looking' substance on leaves
Leaf curl
Leaf drop
Infected fruit and flowers are often aborted or malformed

Biological treatment

Milk is probably the most trusted organic method of combating powdery mildew. Dilute it 1:10 and spray onto plant. Remove, prune out and destroy infected parts. Improve air circulation by thinning and pruning. Don't water plants from above.

Chemical treatment

Fungicides are rarely necessary to manage powdery mildew in a home garden but if you would like protect a special plant choose a fungicide which includes sulfur, lime-sulfur, neem oil, and potassium bicarbonate

Lifecycle

Powdery mildew requires living plant tissue to grow and either spend the winter as dormant infections on green tissue or as resting structures on plant debris and begin producing spores in the spring. These spores are carried to your plants via wind, insects, and splashing water.

Prevention

Mulch and water to reduce plant stress but do not fertilize as powdery mildew favors young, succulent growth Try to find a powdery mildew-resistant cultivar. Don't plant non-resistant varieties in the shade.
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Knowledge and advice

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