Hi - I had a magnolia bush planted in the front of my house about 5 years ago. The bush has always been very healthy. This summer I noticed a grayish substance on the leaves. At first it was just a few, but, it's pretty widespread right now. Could this be a fungus, and if so, is there anything I can do to help it? Thanks, Mary

You could be describing Powdery Mildew, a fungus that when the weather is just right grows on the surface of leaves and can be rubbed off. the disease is still present inside the leaf cells. There are other leaf blights and molds, but PM is pretty common. You could take some impacted leaves to a good garden center and see what they have to say or send fresh samples yet this year or when it first appears to a University plant clinic for identification. This fall, rake up and dispose of the magnolia leaves to lessen the source of infection next spring. The University of Illinois Plant clinic http://web.extension.illinois.edu/plantclinic/