Growth on tree?
Thank you for your question and your picture.
This appears to be leafy gall.
Leafy gall is a disease caused by the bacterium Rhodococcus fascians, which enters the plant through wounds in roots or stems and stimulates the plant tissues to grow in a disorganized way, producing dense clusters of distorted, leafy shoots.
Currently there is no control. You can cut out the infected areas making sure you sterilize your cutting tool both between each cut and after completion. Then you will need to wait and see if the tree recovers next season.