Botrytis blight or gray mold is a fungus disease which infects a wide array of herbaceous annual and perennial plants. There are several species of the fungus Botrytis which can cause blights; the most common is Botrytis cinerea. Botrytis infections are favored by cool, rainy spring and summer weather usually around 60F. Gray mold can be particularly damaging when rainy, drizzly weather continues over several days. During wet or humid weather, examine any brown or spotted plant material that develops, and look for masses of silver-gray spores on the dead or dying tissue. These spores are readily liberated, and may appear as a dust coming off of heavily infected plant material. Sanitation is the first important step. Remove dead or dying tissue from the plants and from the soil surface. Fungicide spray treatments can also help.