Dealing with Mildew on Bee Balm Leaves

Bee balm (Monarda) is a gorgeous perennial loved for its colorful, nectar-rich flowers that attract pollinators. Hummingbirds, butterflies, and bees flock to the red, pink, purple, and white blooms. However, bee balm is prone to powdery mildew, a common fungal disease. If left unchecked, powdery mildew can cover leaves in an unsightly white residue, weakening and eventually killing the plant.

What Causes Powdery Mildew on Bee Balm?

Powdery mildew is caused by various fungal organisms in the Erysiphales order. The fungi overwinter in plant debris left on the ground. In spring, wind, splashing water, and insects spread the spores. When humidity is high (over 90%), temperatures are moderate (68°F to 81°F), and air circulation is poor, the spores germinate on bee balm and other susceptible plants.

The mildew starts out as small white patches on upper leaf surfaces. It quickly spreads to coat the entire leaf in a dry, powdery sheen. Leaves eventually yellow, wither, and die back. While the iconic flowers continue blooming, the plant’s health declines. Prompt identification and treatment of powdery mildew are key to saving affected bee balms.

Identifying Powdery Mildew

Learn to recognize the symptoms of powdery mildew on bee balm:

• White or gray powdery blotches on upper leaf surfaces
• Blotches rapidly spreading to cover whole leaves
• Leaves feeling dry and dusty
• Advanced cases coating all leaves
• Leaves turning yellow, then browning
• Leaves curling up, shriveling, and dying back
• Defoliation progressing from bottom up
• Flowers persisting despite leaf damage
• Spores wiping off easily to show healthy tissue
• Ideal cool, humid, still conditions for mildew

Powdery Mildew Resistant Bee Balm Varieties

Selecting resistant varieties is the best defense against powdery mildew. Look for these top-rated mildew-tolerant bee balms:

• Marshall’s Delight (deep pink blooms, most resistant)
• Blue Stocking (lavender-blue flowers, compact)
• Raspberry Wine (fuchsia blooms, wine-red stems)
• Violet Queen (rich violet-purple blooms)

Check plant tags and descriptions for powdery mildew resistance, Site resistant bee balms in full sun with good air movement,

Preventing Powdery Mildew on Bee Balm

Cultural practices can deter powdery mildew in existing bee balm plantings

• Prune for open structure and airflow
• Space plants appropriately – avoid crowding
• Grow in full sun
• Water at soil level – don’t wet foliage
• Apply mulch to prevent water splashing on leaves
• Discard infected leaves and stems
• Clean up debris thoroughly each fall

Treating Powdery Mildew on Bee Balm

If powdery mildew appears, take prompt action:

• Remove badly infected leaves and discard (don’t compost)
• Apply organic fungicides like neem oil, sulfur, or baking soda weekly
• Use commercial fungicides labeled for powdery mildew
• Improve airflow with small fans if humidity is high
• Avoid overhead watering to limit spore spread
• Reduce treatment frequency as mildew improves
• Inspect regularly to spot recurrence

Vigilance is required to minimize powdery mildew impacts on bee balm. Combining resistant varieties, preventive care, and immediate treatment provides the best control of this stubborn fungal disease. With a proactive integrated approach, you can continue enjoying the beauty of healthy, vigorous bee balms.