Questionhow do i get rid of worms on a river birch
AnswerThis sounds like birch sawfly. They feed in groups and can defoliate a tree. For small trees you can just pick the caterpillars off and destroy them. For larger trees I would spray the foliage with an insecticide called Orthene. This will kill the caterpillars . Check with your local nursery/garden type store for this product.