July 13, 2011

A gardening friend emailed me this morning about the powdery mildew on her butternut squash vines. We spoke and she asked about the treatment I had suggested earlier this garden season. The image above is from her garden. She grows wonderful winter squash every year. Some now are about nine inches long, but need more time on the vine, healthy vines.

Richard Frost of PlantsThatProduce.com offers a treatment to control powdery mildew in his column Got Cucurbitoids? He suggests mixing one tablespoon sodium-free baking powder* with one gallon water and misting the leaves every other week. Another recipe uses one teaspoon baking soda with a few drops of vegetable oil in one quart of water which is then sprayed on leaves.

The UC Davis Integrated Pest Management website has a Quick Tips PDF on Powdery Mildew. To prevent powdery mildew grow plants in sunny locations and provide good air circulation. Remove infected leaves and grow resistant varieties when available.

*Sodium-free baking powder contains potassium bicarbonate and monocalcium phosphate.