Diagnose: Watermelon Powdery Mildew

1. Look for expanding surface colonies on older leaves
2. Powdery mildew begins as separate white patches that merge into a dusty coating on upper and lower leaf surfaces and petioles. Normal rind or leaf pattern stays within the tissue, spray residue follows droplets, and downy mildew starts with angular yellow lesions bounded by veins rather than a uniform floury film.

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