I have a customer that I sometimes work for and he is asking me about spraying his hemlocks. They are about 10 to 12' tall. He lost one last year and his son told him that they need to be sprayed for a pest that he described as being white in color that infects and sucks from the foliage area. I am not sure as to what he is referring to. Only one out of several in a row has died. He described it as slowly over time loosing its color thus leading to the tree dying. Any ideas?