If you notice a white or gray film on your plant’s leaves – almost as if they are covered in a thin film of baby powder or flour – there’s a good chance that the plant is suffering from powdery mildew, a fungal disease made up of spores, also known as Blumeria graminis. Powdery mildew can affect several different types of vegetables, flowers, shrubs, and tree leaves. It can spread to similar species of plants in your landscape by the wind, insects, and even water.
Powdery mildew can cause the plant’s growth and flowering to be stunted. Severely impacted plants may see their leaves twist, curl, turn yellow, and eventually fall off.
What Causes Powdery Mildew?
The spores that cause powdery mildew usually live on plants in shaded areas or in spaces where plants are crowded together, reducing airflow around the plant. Plants growing in dry areas during the day but then high humidity in the evenings may be highly susceptible to powdery mildew.
How to Prevent Powdery Mildew
When planting flowers, shrubs, and trees that may be susceptible to powdery mildew, choose sunny areas with good drainage. This will reduce the amount of humidity around the plant. Try to avoid crowding plants together, giving them room to grow and air to circulate around them. Pruning back the plant to allow increased sunlight and airflow can also help. Avoid overwatering the plant. Aim for the base of the plant to soak the roots, not the leaves. Soaking the leaves can increase the humidity around the plant, inviting the spores to grow.
Pruning back infected leaves can also help. However, it is essential to dispose of the infected leaves. Don’t leave them on the ground or around the base of the plant because the spores can become airborne and infect the same plant or another one.
Effective treatment takes place in the spring before the disease has time to spread to newly emerging leaves. A fungicide spray, properly applied and timed correctly, can help keep the disease under control and stop it from spreading to similar plants in your landscape. Trees that are severely impacted may require several applications to bring the disease under control.
Please contact us to learn more about controlling the spread of powdery mildew in your landscape.