Diagnose: Powdery Mildew on Cucumber

1. Powdery mildew when white surface colonies expand across older leaves
2. Look for separate white patches that enlarge and merge on the upper or lower leaf surface. Powdery mildew becomes more convincing when the growth spreads between inspections, while angular yellow lesions, fixed silver mottling, webbing, or a deposit that follows spray droplets point elsewhere.

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