Mold, or what is more commonly called white powdery mildew, can infect your bee balm plants. Most often it is not fatal to the infected plant, but it certainly can ruin the visual aesthetics of your yard or garden. While you may not be able to keep white mold from forming on your bee balm, there are ways to diminish its appearance.
Rinse off plants with a strong spray from the hose. Not too strong -- you don't want to further damage them -- but strong enough to cause the plant to lilt a little when hit by the stream of water.
Trim off any moldy areas that are turning brown. Do not put these in your compost pile; the mold will spread to other plants when using the finished compost. Bag and put in trash.
Spray with hydrogen peroxide. Use regular hydrogen peroxide that is available at drugstores. Do not substitute "food grade" hydrogen peroxide. After using water to remove as much mold as possible, spray the plants with full strength hydrogen peroxide. Make sure to get the tops and undersides of the leaves, as well as the stems. Use weekly to help prevent mold from forming.
Spray with a milk mixture anti-fungicide. Mix 1 part milk and 1 part water. Spray plants every three to four days at the first sign of white powder. Milk changes the pH of the surface of the leaves, thereby preventing the mold from adhering to them.
Make sure your bee balm plant has a lot of room to breathe to keep mold from returning. Trim or remove neighboring plants to allow good air flow all around the affected plants.