Why Are My Roses Molding?

Your roses are likely molding due to a fungal disease, most probably rose powdery mildew.

Understanding Rose Powdery Mildew

Powdery mildew is a common fungal disease affecting roses and is characterized by a white or gray powdery growth on leaves, stems, and buds. This is why it appears as if your roses are molding.

How Powdery Mildew Spreads

• Airborne Spores: The disease spreads through microscopic, airborne spores produced on the powdery growth.
• Dry Conditions: Unlike many fungal diseases, powdery mildew doesn't need extended periods of leaf wetness to thrive. It can be a problem during dry summers, as noted in the reference.
• Growing Season: Powdery mildew actively spreads throughout the growing season.

Signs of Powdery Mildew

• White or Gray Powdery Growth: Look for powdery, mold-like patches on various parts of the rose plant.
• Distorted Leaves: Severely affected leaves may become distorted or curled.
• Reduced Bloom: The disease can weaken the plant, leading to fewer and smaller blooms.

Managing Powdery Mildew

Here are some steps you can take to manage powdery mildew:

• Increase Air Circulation: Prune your roses to ensure good air circulation around and through the plant.
• Remove Infected Parts: Immediately remove any leaves, stems, or buds that show signs of mildew.
• Fungicides: Use organic or chemical fungicides labeled for powdery mildew, following the instructions carefully.
  • Apply fungicides early in the season or as soon as you notice the first signs of infection.
  • Reapply as directed, especially after rain or watering.
• Watering Practices: Water at the base of the plant, avoiding wetting the leaves.
• Resistant Varieties: Consider planting rose varieties that are resistant to powdery mildew.