Most plant growers will come into contact with a white dusty mold growth on plant leaf surfaces at one time or another. This plant disease is known as powdery mildew, and it is caused by fungi from the genus Oidium.
Many outdoor plants may be affected in any given year. African violet, grape ivy, and begonia are the most common indoor plants that are affected by Powdery Mildew.
Initially the plants leaves are covered by a white to grayish dusty growth that can easily be rubbed off. Nutrients are removed from the plant by the fungus and severe infections can result in deformation of the stalks and leaves of the plant.
Method of Spreading
Powdery mildew, like all fungi, spreads through the use of spores. The spores are produced in the white patches found on the leaves and from there they spread to other parts of the plant and possibly to other plants of the same species.
Fungi require moisture to grow, so one of the best strategies to minimize powdery mildew infection is to reduce the relative humidity around the plants. This can be partially accomplished by reducing the frequency of watering the plant and reducing the frequency of misting its leaves. Increasing the ventilation around the plant will also lower the humidity and the likelihood of powdery mildew infection.
If your plant has already been affected, the first step you should take is removing any diseased leaves and discarding them in an enclosed bag. This helps minimize the spread of the fungus. Then you can purchase and use a spray on fungicide such as potassium bicarbonate or any product containing neem oil as an active ingredient, and your powdery mildew problem will be no more.
- North Dakota State University: Houseplants Proper Care and Management of Pest Problems
- Cornell University: Powdery Mildew Fact Sheet
plant, fungus, gardening
About this Author
Patrick Way is a freelance writer from Baton Rouge, La., who has been writing professionally since 2009. His work appears in various online publications. He specializes in science writing and holds a Bachelor of Science in biological sciences from Louisiana State University in Baton Rouge.