NDSU Extension Service - Burleigh County

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Powdery Mildew on Plants

Are you starting to see powder on your plants? The powder can be seen as white to gray blotches or spots on the leaves, stems, or buds of the plant. Powdery mildew is a common fungal disease found on several plants from lilacs to squash.

Image:  Powdery Mildew on Pumpkin Leaves by Jeff Kubina, www.flickr.comPowdery mildew is most prevalent when there are humid conditions accompanied with cool temperatures.  It can sometime be seen in warm, dry conditions as well.  It usually is most severe on plants or plant parts that are in shaded areas with poor air movement.  Powdery mildew often affects young plants more severely, you might see your leaves turn yellow and fall off prematurely.

Powdery mildew survives the winter and wind in the spring will release the spores.  Throughout the growing season additional spores are produced and spread as well.  If you have powdery mildew on your plant it will spread to neighboring plants.  Powdery mildew will not do well if leaves are wet from frequent rain or irrigation.

Powdery mildew does not significantly affect your plant’s health.  Management for this fungal disease includes: not overcrowding plants, pruning to increase air circulation, staking plants, and having good sanitation in the garden (destroying affected leaves).  Fungicides are available to use to prevent the spread of powdery mildew.

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