I don't know the why or how on trees having them. When I was growing up my grandparent's had 2 massive catalpa trees at the back of their yard. One was about the size of CRJ1960's picture, the other was a little smaller. They were both covered in worms every summer for a short time. They were never cut back or pruned. It was always amazing to me how many worms would be on them for a short time in the summer and how they'd eat that many leaves off of the trees that quickly. The trees never died, at least while my grandparents still lived there...no idea if the trees or still there now.
My dad has a couple of transplants from those trees. I know he has worms on his most years but I haven't kept up with how many or how often. I need to go take a look and ask him about them.
