Thursday, July 12, 2012 By: David Velten

Powdery Mildew in the Garden

The July 5, 2012 issue of the UMass Vegetable Notes reports that powdery mildew has reached Central MA and you should check your summer squash for symptoms. Sure enough, we can report that powdery mildew (PM) is now affecting at least zucchini in the Bolton Community Garden. Here are some pictures of what it looks like on summer squash. PM will affect any of the cucurbits and a lot of other garden plants including beans, peas, and broccoli.


The best solution to powdery mildew is to prevent it from appearing. First of all, select varieties that are described as being resistant to powdery mildew, such as cucumber Diva and yellow squash Success, Sunray or Sunglo. Make sure plants have adequate spacing for good airflow. When powdery mildew is reported in the area, spray plants to prevent infection. It is easier to prevent infection than cure it. If plants are heavily infected, remove the most affected leaves and dispose of them in the trash, NOT in the compost bin. Spray with a fungicide.

An organic solution that is reported to be effective in preventing PM is easy to mix up. For a quart of spray, add milk (any kind) to water at a ratio of one part milk to nine parts water (4 ounces milk to 28 ounces water). Don’t use higher concentrations because it can cause the growth of other diseases. To the solution, add a tablespoon of baking soda and a couple of drops of dish soap. If you have it, add a teaspoon of neem oil, which has fungicidal properties. Spray this mixture on plants in the morning so it can dry adequately before nightfall. Repeat spray weekly. This is a preventative method, so spray now even if you are not currently affected by mildew Spray at least squash, pumpkins, melons and cucumbers now and monitor other susceptible plants.


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