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Identifying and Managing Downy Mildew on Cucumbers and Squash

Your symptoms—angular yellow spots bounded by veins, gray-white fuzz on leaf undersides—point to downy mildew, not cucumber mosaic virus (which causes warty, mottled fruit). Downy mildew thrives in heat and humidity. Fruit is safe to eat if normal. Control with labeled fungicides.

About Gardening: Solving Cucumber Fruit Drop: Pollination and Heat Stress; Preventing and Managing Powdery Mildew on Cucumbers; Downy Mildew (Peronospora/Plasmopara): Water-Dependent, Algae-Related Disease; Downy Mildew: Cool-Weather Obligate Parasites of Ornamentals; Choosing Mildew-Resistant Phlox for Hassle-Free Perennials; Twin Cucumbers: A Natural Curiosity; Callery Pear Fruit: What Those Tiny Pears Really Are; Downy Mildew on Zucchini: Act Fast to Save the Crop; Impatiens Downy Mildew: Best Substitute Plants; Impatiens Downy Mildew: Identification, Management, and Alternatives

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