Question
I have a 3yr. old poplar tree that is invested with an insect.  The top of the leaves look as if some one sprinkled charcoal dust on them ..but it doesn't wipe off.  The bottom side is still green. On the branches there are red bumps that when you touch them it looks like blood on your hand.  I thought i saw a minute  spider looking insect on the under side of the leaf.  It appeared to have a green tint to it  What can I spray on the tree to get ride of this insect?

Answer
Sounds like spider mites.
Spider mites have tiny mouthparts modified for piercing individual plant cells and removing the contents. This results in tiny yellow or white speckles. When many of these feeding spots occur near each other, the foliage takes on a yellow or bronzed cast. Once the foliage of a plant becomes bronzed, it often drops prematurely.

Chemical Control - Miticides Spider mites are usually not killed by regular insecticides, so be sure to check the pesticide label to see if "miticide" is present. Pesticides claiming "for mite suppression" are usually weak miticides and will not perform well. There are few products available to the homeowner. Dicofol (=Kelthane) is registered for over-the-counter use but is difficult to find. Acephate (=Orthene), dimethoate (=Cygon), chlorpyrifos (=Dursban), diazinon, disulfoton (=Di-syston), and malathion have over-the-counter product labels but are considered weak miticides.