Garden Pests and Diseases: Strange growth on willow, 0 by AKelley

AKelley wrote:
Hi......I'll mention that I have also posted this question under the trees & shrubs forum.

I noticed this morning that I have this growth on the trunk of my willow tree, which we planted the year before last. It's done well and grows like crazy. We planted it in a spot in our yard that holds water pretty bad after rain, which we've had a ton of lately.
Can someone please tell me what this is? Since I've noticed it, I've thought of nothing else...It really bothers me. I love this little tree. Please help : )

Thanks in advance, Angie