Question
We have a honelocust tree planted ~ 16 years old and has several mossy green patches on the Base of the tree and has several little green bugs all over the tree. Has always been a very healthy tree.  Still has new growth, though.  We have had to trim the branches several times due to massive growth onto roof and overhanging the drive.
What is this mossy stuff growing on the tree and the little green bugs? Can it be treated? If yes, What kind of treatment?

Answer
Mossy green stuff are fungus spores which are common.  One thing you said though is what worries me.  You said you recently trimmed the tree.  Improper trimming is the leading cause of bacterial infections entering th tree like Hypoxylin Canker and others.  Please make sure the cuts were done with a sharp chain and there were no tearing or scarring of the limbs.  The little green bugs are maybe beetles and will bore through the cambium layer of the tree which will also invite infections.  I would recommend maybe 7 dust for those guys.  

If any cuts were made revealing dead tissue or rotting limbs make sure you cut back to where the good tissue is.
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James