Treating Powdery Mildew on Knockout Roses with Baking Soda

White powdery substance on Knockout rose stems dries up blooms. Gardener seeks spray recommendations.

Diagnosis: Powdery Mildew

A fungal disease favored by warm days and cool nights.

Home Remedy

Mix 1 tablespoon baking soda in 2 quarts water; spray every 3 days (daily if persistent).

Cultural Practices

• Water deeply at base—avoid wetting foliage.
• Sprinklers spread mildew; use soaker hoses.
• If baking soda fails, use a commercial rose fungicide labeled for mildew.

Good air circulation and dry leaves prevent recurrence.