08/28/2026
π«§ If the leaves on your squash, pumpkin, or cucumber vines are starting to look dusted in white, you're not imagining it. Powdery mildew is active in Gorge gardens right now, and late summer's cooling nights and lingering humidity are exactly the conditions it favors.
The disease shows up first as small white circular spots on leaf surfaces, usually starting on older or shaded leaves, then spreads to cover most of the leaf and eventually kills it off. (It appears on both vegetables and ornamentals.) It won't touch the fruit directly, but heavily infected plants lose the leaf cover that protects fruit from sunscald and won't finish ripening as well.
πΏ There's no cure, but you can slow it down. Remove and destroy the worst-affected leaves rather than composting them, avoid overhead watering that wets the foliage, and increase airflow by thinning out crowded growth. A baking soda spray (about 4 teaspoons per 2 gallons of water) applied every 7-10 days can also help suppress it.
π₯ If you're planting cucurbits again next year, look for varieties bred with some resistance, it won't stop the disease entirely, but it buys you more time before symptoms take over.
π§ Search "OSU powdery mildew squash" for full identification photos and control options. Garden questions? call 541-386-3343 or visit extension.oregonstate.edu/mg/hoodriver. The Central Gorge Master Gardener program is a service of OSU Hood River County Extension.
For garden inspiration and motivation, join our 3rd Annual Hood River Garden Tour on Saturday September 12th!
πΊ Visit our website to learn more and see details and this year's map!