Question
I have a large liquid amber tree growing in the back yard. I recently noticed that some of the leaves have been curled up and joined together. They almost look like a sack or cocoon. Do you know what causes this and does the tree need to be treated?

Answer
These sound like leaf rollers. They may cause some growth loss but will not kill the tree or cause die back. A liquid Sevin spray or Bt spray could be used but since most trees are too large to reach the foliage to cover all leaves it is normally not practicable. I would do nothing since the insect really does very little to the tree and the population varies greatly and more than likely will not be around next year.