If you moisten your fingers, then smear one of those frass pellets, you'll see that they are really green and not black. Highly concentrated recycled bean leaves.

Ok, I took some pics today and will try to get better shots if these aren't good enough. The tree looks to be over 30 ft tall and doesn't look like a weeping willow to me but she says it is. The bugs are black about a fourth of an inch long. My camera battery went kaput as soon as I got to the tree so I didn't get many pictures. The first pic is the white stuff on the branch. The second one is the white stuff on the ground and then a pic of the tree. I hope these help you guys. Thanks, Judy

Your member page has no information as to where you are so I really have no idea what pests might be in your area. Sorry, Carolyn

They could be carpet beetles. Here's a fact sheet on carpet beetles so you can compare to what you have.