Treating Downy Mildew on Black Baccara Roses: Organic and Chemical Options

White dust on leaves in humid conditions is downy mildew.

Spray daily with 2 tablespoons baking soda in 1 gallon water, covering leaf undersides, until spots disappear.
If persistent, apply any rose fungicide labeled for mildew.

Roses: Heirloom Rose Bush with Black Spot: Sanitation and Fungicide Program; Gardenia with Webbing, Black Buds, and Leaf Drop: Spider Mites and Sooty Mold; Sooty Mold on Foxtail Palms: Caused by Scale or Aphids; Camellia Black Coating: Sooty Mold from Aphids; Sooty Mold on Crepe Myrtle & Gardenia: Aphid Control; Aloe Vera Brown Spots: Insect Damage, Not Fungus; Climbing Rose Blooming But No Leaves: Animal Ate Them; Growing 'Black Baccara' Rose: Indoor Challenges and Cold Climate Limits; The Truth About Black Roses and the Rainbow of Rose Colors; Black Film on Multiple Trees: Sooty Mold from Scale/Aphids

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