I live in Toronto and have a 25 year old euonymus which has started to drop its leaves during the summer. The leaves turn yellow and have a few brown spots and also some white 1mm rectangular shallow growths that look like pieces of feather. I have looked it up and think it may be powdery mildew. What should I do to save it?
Thank you for contacting Toronto Master Gardeners.
From your picture it looks like you have scale, the most common disease to affect Euonymus. I have attached a link to a comprehensive article previously posted on Toronto Master Gardeners site which walks you through the steps for dealing with this problem. There are also some valuable links to sites which outline the life cycle of the scale for you and includes pictures to help with identification.
Good luck and I hope this helps.