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Controlling Powdery Mildew

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Controlling Powdery Mildew

As a gardener living in St. Louis with wet springs and humid summers, you get use to pests, insects, disease and other problems. But the one problem that bothers me the most is powdery mildew. Crowded plants with poor air circulation, dampness and high humidity help encourage growth. Powdery mildew is a fungus that can overwinter in plant debris which produces spores in the spring. The spores are carried by wind, insects and splashing water.

Some ways to control powdery mildew include: Choose healthy plants and keep them growing healthy. Try to find a powdery mildew resistant cultivar. Improve air circulation by thinning and pruning. Water plants at the soil level, not from above. Powdery mildew loves young, new growth so don’t fertilize until the problem is corrected. Remove and destroy all infected plant material and DO NOT COMPOST.

There are many fungicides available to treat powdery mildew. Check the label to be sure they are safe for that infected plant. Some ingredients listed are: potassium bicarbonate, neem oil, sulfur or copper. There are also some home remedies made from baking soda or milk that are effective.

Baking soda spray
1 tablespoon of baking soda
½ teaspoon of liquid soap
1 gallon of water
It raises the pH, which stops powdery mildew growth.


Milk spray
1 part milk
9 parts water
Spray the stems and tops of leaves and reapply after a rain.

Powdery mildew is not fatal but if it comes back continually, the plant becomes stressed and weakened. Infected leaves will fall off when photosynthesis is blocked. On edible plants, the flavor of the fruit or vegetable will change. Or if the buds are infected, they may not mature at all.

A good resource for garden pests is the Advice, Tips and Resources  page found in Gardening Help. It has detailed information on all the pests that might decide to visit your garden.

Debbie Kirkpatrick, Kemper Horticulture Assistant

| Categories: Summer | Tags: diesease, powdery mildew | View Count: (6919) | Return
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