There are numerous diseases that can infest your flowers and affect their health and appearance. The most common time for these diseases to attack are mid to late summer, when humidity is at its highest. The best defense against these common flower diseases is to make sure your garden's environment is not conducive to their development in the first place. Also, choosing disease-resistant cultivars will help decrease the chances of these diseases taking hold in your flower gardens.
Powdery mildew shows up on the leaves of flowering plants and, as it progresses, the University of Vermont Extension warns, it can spread to the stems and flowers of the plant. The disease causes leaves to first turn yellow, then brown and eventually die. While powdery mildew will not kill the plant, it weakens it overtime if untreated and makes the plant susceptible to other problems. To avoid powdery mildew, space individual plants far enough away from each other to allow for optimum air circulation, as powdery mildew thrives in humidity. If necessary, treat this disease by spraying the plants with a fungicide.
Gray mold is the most common disease affecting flowers. A combination of cold temperatures and high humidity provide a perfect breeding ground for these spores. Gray mold, as the name suggests, will show as a growth of gray-colored mold on plants. It is also commonly found on dying flowers and leaves. As with powdery mildew, proper air circulation between plants will help avoid this disease. The spores of gray mold are transferred via water droplets and the air. To prevent gray mold, water your flowers early in the day, to allow the plants to dry before the cooler night temperatures arrive. It also helps if you clean up expired blooms and leaves immediately.
Root rot is a common flower disease brought on by either improper moisture levels in the soil or the presence of a fungi within the soil itself. Common signs of root rot include the appearance of dull leaves, which turn yellow and eventually wilt. The spread of root rot can happen quickly, if the entire root system of the plant is affected, or gradually if only the smaller, feeder roots are infected. Dig up flowering plants displaying the described symptoms to determine if root rot is the cause. Examine the color of the roots--if they appear brown and mushy they are likely infected. Healthy roots should be firm and white in color. To avoid or correct root rot, improve the drainage of the soil by introducing lighter materials, such as peat moss, into the soil. Water flowers enough to keep the soil moist, but never soggy.