Question
We have a large pussy willow tree in our yard and have noticed this year that there are small black bugs on over half of the branches.  They create quite a mess on the ground underneath them.  What are they and how do we get rid of them?

Answer
Sounds like willow flea beetles. Spray the foliage with an insecticide. Insecticides containing carbaryl (Sevin), spinosad, bifenthrin and permethrin can provide fairly good control.  These are contact insecticides.
But I would use an insecticide called  Orthene this is a systemic type and will last longer than the contact insecticides.and you may have to spray a couple of times about a week apart to make sure you cover all the beetles present.
They will not kill the tree unless there is several years of complete defoliation.  

Check with your local nursery/garden type store for these products for flea beetles.