This is powdery mildew, a fungal disease, and I’ve spotted it in our garden.
Not only is it unappealing, it can reduce a plant’s production of vegetables and impact flavor.
What can we do?
We can control it, but not cure it once it appears. To start, I took off the leaves most affected on the pumpkins, zucchini and squash. I threw these away in the trash bin next to the rec building to get them out of the garden. Don’t compost diseased leaves of any kind.
Next I spread the vine so the remaining leaves will get maximum sun exposure and good air circulation. This should inhibit spore germination.
I thought we could try an experiment and compare two methods touted online as slowing the spread of powdery mildew.
In one plot, we will spray the remaining leaves and stem with a cow’s milk spray made with 3 parts milk and 7 parts water.
In another plot, we will spray with a mix of 1 teaspoon baking soda in 1 quart water.
Both methods reportedly create an environment that inhibits the spread of this disease and are best started before powdery mildew appears.
I will mark the beds to indicate what is being used and we can compare notes in a few weeks.
For Future Reference: Gardeners can purchase resistant varieties at the start of the season. While resistant doesn’t mean the plant won’t get powdery mildew, it does mean they are less susceptible.