In early spring to summer, a white to grayish-white powder may start to appear on your azalea, blueberry, and squash plants. This could be powdery mildew and it is fairly harmless to your plants unless severe. It thrives in warm, humid conditions, and there are some non-chemical practices to avoid this pesky powder such as spacing your plants appropriately, regularly pruning branches, and making sure your plants that love the sun see it for at least 6 hours a day.
See a Grayish Powder on Your Plants? It’s Probably Powdery Mildew