Powdery mildew is a fungal disease that can reduce the vigor and productivity of apple trees. Young trees and fast-growing trees are more susceptible to powdery mildew. The disease reduces the speed of new growth and causes leaf deformity and web-like scarring on mature fruits. Powdery mildew can overwinter in previously affected growth.
Watch developing apple trees for signs of powdery mildew. Affected leaves will develop gray or white splotches on both sides. These markings can also appear on buds, flowers or shoots. This is the most easily recognizable sign that your tree is affected by powdery mildew.
You control powdery mildew only when you know for sure you had the disease last year. If you did not have the disease last year you wait until you see the symptoms and then begin the bi-weekly spray of Actinovate. That is a new fungicide available that will prevent powdery mildew from doing any damage to your apple tree. It is a biological fungicide using beneficial microbes to attack and control the powdery mildew fungi.
One Week Before Bloom Begins – Spray the tree with Actinovate. Wait until petal fall and then repeat the spray every two weeks until harvest.