Knockout Roses Dying After White Webby Substance: Mildew, Not Death

Healthy Knockouts for years. This year: white filmy web on tops, "melted" when touched. Gone now, but bushes dying. Asks what it was and how to save.

White Web = Mildew (Likely Downy)

• Powdery mildew: White powder, high humidity + warm.
• Downy mildew: Gray-white fuzz underside, purple blotches top, defoliates in 1 day. Cool, wet weather.

Treatment

• Funginex (if legal in state).
• Copper spray now.
• Dormant oil + sulfur in early spring.
• Organic: 1 tbsp baking soda / 1 gal water.

"Dying" = Defoliation, Not Death

Leaf drop ≠ plant death. Roses regrow 3 leaf sets without vigor loss. Canes hard/brown = dead. Canes green = alive.