Bee balm is the common name for a fragrant flowering plant in the Monarda genus. Also called bergamot and Oswego tea, it was the plant the American colonists used when they stopped using black tea in protest of British taxation. In addition to having a pleasant taste, this herb has been used to treat colds and sore throats. It’s a small, attractive plant with red flowers, which attract butterflies, bees and hummingbirds. But it can develop powdery mildew. When this happens, you can stop the mildew's spread with several simple remedies.
Grow your bee balm plant in soil that is moist, slightly acidic and rich with organic materials to keep it healthy and better able to resist plant diseases such as powdery mildew. Bee balm also thrives in areas that have partial shade to full sun.
Spray your bee balm with a combination of milk and water once each week if you notice a fuzzy white or gray coating on the leaves, stems or flowers. Stir 1/2 cup milk, either skim or whole, into 1 gallon of water and then drench your plant thoroughly. The milk and water spray works, according to online resource Pioneer Thinking, because the lactobacillus in the milk will grow on the leaves, leaving no opportunity for mildew spores to gain a foothold.
Spray your plant with a purchased fungicide, such as one with potassium bicarbonate. You must use fungicides before the mildew appears or as soon as you notice it because they do not normally succeed in getting rid of established mildew.
Keep the growing area cleaned up of leaves and other plant parts that have fallen due to powdery mildew. Burn or discard debris in the fall to prevent further outbreaks of this disease. Do not add diseased plant parts to your compost pile.