I have a well-established (over 17 years old) forsythia bush in my garden. A few days ago, I decided to prune it down to around 4ft tall as it was well over 8ft and has recently finished flowering. This morning, I noticed some fungus (looks a bit like mushrooms/toadstools) - around 5 pieces growing in a clump around the top of one of the branches. I've googled it, and it looks like Honey Fungus, however, I'm not too sure what to do about it? Do I just cut that whole branch down to the root or is there something that I can use to kill the fungus? Thank you.