Garden Pests and Diseases: Potted willow tree dying, 1 by sidneyalliance

sidneyalliance wrote:
I have 3 young potted Willow tree, one die already, it fell all leaves and got dried brown branches. One still health and one starting die like the first one, but still with some leaves yet. I notice those small webs in the plant and very small transparent insect moving there. What is this? I\'m guessing this is what killing the plant. Once the health one doesn\'t have.
What I need to do to save the tree and prevent the health one to catch it?
Any help will be great appreciated. Thx.