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If you’ve grown bee balm you probably know about powdery mildew. This fungal disease produces a powdery white film on the leaves. This prevents sunlight from reaching the leaves that can eventually yellow and brown. Fortunately, you can reduce your problem with proper selection, siting and spacing.
Start by selecting powdery mildew resistant varieties whenever possible. They found that Claire Grace, Marshall’s Delight, and Stone’s Throw Pink were the toughest plants early in the season. Marshall’s Delight, Blue Stocking, Cambridge Scarlet, Elsie’s Lavender, Mahogany, and Vintage White all continued to do well as the season went on.
Reduce problems on existing plants by growing them in full sun. Give the plants plenty of room to increase air circulation and light reaching the plant. Improving the growing conditions can help reduce disease problems.
A bit more information: Further decrease the risk of powdery mildew with a bit of spring thinning. In early spring, cut off about ¼ of the stems to let more air and light into the plant. This will encourage sturdier stems and discourage disease problems.
As a bee balm plant owner you’ve likely noticed a telltale white powdery coating on the leaves of your prized Monarda flowers. This substance is almost certainly powdery mildew a common fungal disease that affects many garden plants. Learning to recognize, treat, and prevent powdery mildew is key to keeping your bee balm healthy and blooming its best.
What Causes Powdery Mildew on Bee Balm?
Powdery mildew is caused by various fungal organisms in the Erysiphales order. The fungi overwinter in fallen leaves, stems, and other debris. In spring, spores are spread by wind currents, splashing water, and insects. When conditions are favorable – dampness, shade, and poor air circulation – the spores germinate on susceptible plants like bee balm.
The fungi thrive in humidity levels above 90% and temperatures from 68°F to 81°F. Once established, powdery mildew coats leaf surfaces with white or gray blotches that can spread to cover entire leaves. Eventually leaves shrivel and die, harming the plant’s vigor and appearance.
Identifying Powdery Mildew Fungus
Learning to recognize powdery mildew is vital for prompt treatment. In addition to the namesake white powdery coating, look for these symptoms:
- White patches first appearing on upper leaf surfaces and spreading rapidly
- Affected leaf areas taking on a dry, dusty texture
- Advanced cases covering entire leaves in powdery growth
- Leaves turning yellow, browning, curling, and dying back
- Defoliation occurring from the bottom of the plant upward
- New shoots and flowers still appearing despite leaf damage
- Spores easily wiped away to reveal healthy tissue underneath
- Cool, shady, still conditions encouraging fungus growth
Powdery Mildew Resistant Bee Balm Cultivars
The best defense against powdery mildew is to select resistant Monarda varieties like:
- Marshall’s Delight – Deep pink flowers, purportedly the most resistant
- Blue Stocking – Lavender-blue blooms, compact habit
- Raspberry Wine – Fuchsia blooms with wine red stems
- Violet Queen – Rich violet-purple flowers, less prone to mildew
Check tags or plant descriptions to confirm powdery mildew resistance when buying bee balms. Site resistant varieties in sunny spots with good airflow.
Cultural Controls for Powdery Mildew
For existing plants, proper care can help deter powdery mildew:
- Prune for open structure and airflow
- Space plants appropriately – avoid crowding
- Grow in full sun
- Water at soil level, avoiding wetting leaves
- Apply mulch to prevent water splashing onto leaves
- Remove and destroy infected leaves/stems
- Clean up debris thoroughly each fall
Treating Powdery Mildew on Bee Balm Leaves
If powdery mildew appears, take action quickly:
- 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 as directed
- Improve air circulation with small fans if humidity is high
- Avoid overhead watering to limit spore spread
- Reduce frequency if mildew improves but inspect regularly
Combining resistant varieties, preventive care, and prompt treatment at first signs of mildew provides the best control. With diligence, you can minimize impacts and keep your bee balm beautiful.
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FAQ
How do you treat powdery mildew bee balm?
Should I prune bee balm with powdery mildew?
How do you get rid of powdery mildew without harming bees?
Can powdery mildew affect a bee balm plant?
However, one common problem that can affect bee balm plants is powdery mildew. This fungal disease can cause leaves to become covered in a powdery white substance, stunting growth and reducing the plant’s overall health. Fortunately, there are several steps you can take to prevent powdery mildew from affecting your bee balm plant.
How do you control powdery mildew in bee balms?
When growing bee balms you can control powdery mildew through appropriate cultural practices. These include the following: Plant the bee balm where they will receive at least six hours of sun each day. Ensure that the soil is moist with rich organic matter. Space the plants two to two and half feet apart.
What does powdery mildew on bee balm look like?
In addition to the powdery residue, bee balm powdery mildew can also cause other visible symptoms. These include leaves that turn yellow or brown, twisted or distorted leaf growth, and a general decline in the plant’s overall health and vigor. In severe cases, the plant may lose most of its foliage and become stunted or distorted in growth.
Why are my Bee balm leaves turning white?
The leaves of my bee balm plant are covered with a white substance. The leaves eventually brown and die. New shoots and flowers keep appearing. Should I be concerned? Powdery mildew is the culprit. This is a common fungal disease on lilac, garden phlox, zinnia, squash and other vine crops and lilacs. The good news is the plants will survive.