I have two bald cypress trees in my yard. Both are about 12 years old. Two years ago one developed many small green spheres on the end of the branches as shown in the attached photo. Last year there were only a few. About a month ago they appeared again, more numerous on one tree. As spring approaches, they appear to dry out and crack, revealing a very resinous interior. Photo shows several attached to a branch and one cut in half. What are they and do I have to do something about them?