Why Are My Rose Leaves Yellowing with Black Spots?

If your roses in Topeka, Kansas, are showing yellow leaves and black spot despite regular spraying, the culprit is likely a combination of favorable fungal conditions and chemical overload. Black spot thrives in wet, humid weather—exactly what you've had with heavy rains. However, rotating multiple strong fungicides like Maneb, Daconil, and Ortho Rose Pride can stress the plant further, especially when applied in heat. Daconil in particular can cause phytotoxicity in high temperatures.

Simplify Your Spray Routine

Stick to one product: Ortho Rose Pride is the least toxic of the three and effective against black spot. Give your roses a complete break from all chemicals for 2–3 weeks to recover. During this time, ensure good air circulation, remove fallen leaves, and water at the base to keep foliage dry. Once the plant shows new healthy growth, resume a preventative spray schedule every 7–10 days using only Ortho Rose Pride, applied in early morning or evening when temperatures are below 85°F.

Cultural Practices to Reduce Disease

• Prune to open the center of the bush for airflow.
• Mulch to prevent soil splash onto leaves.
• Avoid overhead watering; use soaker hoses or drip irrigation.
• Clean up all leaf debris in fall to reduce overwintering spores.

With a simpler regimen and patience, your roses should rebound and bloom beautifully again.