Botrytis cinerea is a fungus responsible as Botrytis blight, gray mold or petal blight that causes flower petals to fade and discolor, damaging them severely. Ornamental garden or potted plants such as white cattleya or corsage orchids infected with this fungal disease feature unsightly blemishes on the otherwise smooth and velvety petals. The presence of leaf blight requires immediate action to keep blooms healthy and looking their best.
The University of Tennessee states that the Cattleya orchid or catts is the most commonly grown orchid in home gardens. Native to Brazil and Mexico where these flowers naturally grow on trees in a range of colors including white, yellow, green, orange and blue. Catts require bright light and direct sunlight to flower, and a daytime temperature between 70 to 85 degrees F and nighttime temperature between 55 to 65 degrees F. Improper water or sanitation make the flower susceptible to Botrytis blight.
The fungus Botrytis cinerea causes brown or black ringed spots on petals on white cattleya orchids. In severe cases, the spots merge together to cover larger areas, forming bigger rings or irregular shapes over floral petals.
According to the University of Tennessee Extension, the plant does not die from the fungal disease, but the spots reduce its beauty, deteriorate its health and makes it vulnerable to other diseases.
According to the website ionopsis.com, excessive moisture or humidity on the cattleya orchid causes Botrytis blight. Persistent water droplets on the leaves due to irrigation or rainfall create the environment conducive to the fungus. The presence of dead plant material or debris around the plant also makes it susceptible to the disease.
The best way to manage the fungal disease is through frequent inspection and proper sanitation methods. Inspect the plant for spotted or damaged parts and discard in a paper bag. Avoid misting and overhead watering. Spray infected plant parts with commercial copper-containing fungicide immediately, although it is usually too late once discoloration of petals occurs and the only solution is to prune infected parts.
Continuous inspection and careful sanitation practices prevent gray mold from afflicting cattleya orchids. Ensure good air circulation to the plant and water in the morning so the foliage and petals are dry by nighttime. Water the plant at soil level and dry accidental drips on the foliage immediately with a terry towel. Remove infected flowers immediately to prevent the spread of this disease.