Is the white substance powdery and can you wipe it off. Hi Sandy - Most likely, these white spots on the leaves are not being caused by a fungus. However, another threat to azaleas, as well as rhododendron and Pieris or andromedas, is azalea bark scale (Eriococcus azaleae). What is Causing Azalea Leaves With White Lacy Pattern? Signs of Powdery Mildew on Azaleas. As these azalea leaf pests move on across the leaf, more and more spots will appear. If your azalea branches are covered with a gray, white or black powder, then your culprit is powdery mildew. Usually by the time a customer brings in their leaf the whole plant has this appearence. Janet Flower Shop Network Plant Expert Reply: First we need to determine if you really have a fungus. Make sure the leaves are receiving adequate sunlight. It is not well understood how the fungus penetrates the growing tissue of azaleas and causes the abnormal growths, but it is likely due to the interaction of hormones and other chemicals. Blackened, twisted branches can indicate azalea blight caused by phomopsis and botryosphaeria fungi. Lace bug damage to azaleas normally occurs on the leaves and will look like silvery, white, or yellow spots. Yellow misting on leaves. Fuzzy white spots on top or under leaves. "Azalea leaf gall" is quite common and first shows up in early spring on new azalea growth and causes the leaves to become distorted and thickened. Assure you’ve planted your Azalea in an area with good air circulation. It looks like damage from azalea lace bug to me. Pruning can also improve circulation and prevent too much moisture accumulation. This may also cause the plants to lose leaves or flowers. Treating Powdery Mildew on Azaleas. If so, you have a fungus called powdery mildew. Every spring, summer and fall, a customer will bring an azlaea leaf to us with this white lacy look. This is caused by these azalea insects, literally sucking small sections of the leaf dry and killing that section of the leaf. Ask the Expert: what would get the white fungus off azaleas , leaf the azalea has white on them , on the leafs is it a fungus , what can spray on them will mild soapy water work. If the canopy of your azalea is thinning or yellowing in places or has some dead branches, look for a crusty covering of scale insects on the stems, or white, waxy egg masses produced by the females (see photos). Have you checked the underside of leaves for leaf sucking insects such as lace bug or aphids?