Diary of an Average Gardener

Powdery Mildew

– Posted in: Garden Tips and Info

What is Powdery Mildew?

Powdery Mildew is a common garden problem. It is a common name for several different varieties of fungi and can infect a multitude of garden plants, including perennials, ornamental shrubs, fruit trees, and vegetables. I have found it on my squash plants and my garden phlox.  The bad news is that there really is no cure once it appears.  The good news is powdery mildew can be controlled fairly easily with a few simple ingredients and it rarely kills the plant.

The mildew can reduce fruit or vegetable yield if left unattended. It has never reduced the blooms on any of my perennials or shrubs. Last summer when it rained constantly, I discovered this mildew on my gardenias, but this year there has not been a trace.  So, while I may not have “cured” the shrubs, there is no evidence of the mildew currently. Perhaps the colder winter and less rain this summer took care of it.

Powdery MildewThis year the only plant on which I have discovered powdery mildew is my garden phlox. Note the white dusting. This is a fairly typical appearance on any plant, tree, or shrub. It appears as circles of white dust, which spreads fairly rapidly if left untreated. For perennials and other ornamental plants and shrubs, it is simply unattractive.

Preventing and Controlling Powdery Mildew

It can be prevented by planting disease resistant plants. That’s good if you can find them, but if not, plant what you want and if powdery mildew appears. Simply control it. Placing plants so that they are well ventilated and have sufficient sun is also key in preventing powdery mildew.

Controlling this fungus is fairly easy. There are a number of commercial products available in both organic and non-organic forms. However, I have found one method that is cheap, easy and organic. Simply add a tablespoon of baking soda to a gallon of water and spray it on the leaves and stems, making sure to get both the top and bottom of the leaves. The baking soda   raises the pH which inhibits the spread of the mildew.  I recently read on an organic gardening site, that using a spray of cow’s milk (1 part milk to 9 parts water) also stops the spread of the spores. I didn’t try this. It seemed to me that the milk might attract ants or other unwanted bugs. I’ll stick to the baking soda.