Brown lesions on Knockout rose canes are likely black spot fungus infecting the stems, not cane canker. The pathogen overwinters on fallen leaves and stem lesions. Knockouts are resistant, not immune—especially when hit by sprinkler irrigation or planted en masse.
Start a black spot spray program now. Prune out affected canes. Rake and remove all fallen leaves each October/November to reduce inoculum.
Rose Black Spot and Aphids: Organic Neem and Cultural Controls
Clearance Rose Bushes with Black Stems and Spots: Black Spot and Canker
Managing Black Spot in Clay Soil Rose Beds: Adjust Watering, Spraying, and Expectations
Black Spot on Knockout Roses – Marketing vs. Reality
Leaf Miners, Black Spot, and Fertilizer Strategy: Organic/Synthetic Rotation
Growing 'Black Baccara' Rose: Indoor Challenges and Cold Climate Limits
Indoor Parade Rose Leaf Loss: Black Spot vs. Environmental Stress
Rose Black Spot: Sulfur First, Then Fungicide
Blackening Cymbidium Spikes: Normal Aging and Bakersfield Growing Tips
Rose Black Spot vs. Bud Blackening: Diagnosis and Dormant Oil Strategy
Identifying and Treating Spots on Rose Leaves
Managing Black Spot on Roses: Prevention and Control Strategies
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