Question
I live in central NJ and see green fungus on my flowering cherry and lilac trees.  Can you recommend a spray or a treatment for these trees? These trees don't look healthy and may be dying.

Answer
Are you familiar with Lichens?  My guess is that is what you are dealing with.  They look light, green-silvery in color and have several textures that range from closely appressed to the bark (where all of it is located, right?) to looking like some little primitive greenish-gray flower like structures sticking up off of the trunk.  If this is the case you are looking at Lichens, which are a symbiotic relationship between a fungus and an algae.  The algae are blue-green, so they conduct photosynthesis and the fungus helps hold the body together and catches minerals in rain water as it runs down the trunk.  These organisms are not parasitic to your trees but rather are an indication that the trees are in a stressed condition, say from drought or old age, or even poor pruning management.  First item of busines is to look at the trees and see if they need pruning.  There should be no limbs criss-crossing one another in the center of the canopy.  If there are limbs like this cut out one or the other.  Take a knife and scrape the bark of the limbs, if there is green or cream colored tissue underneath the bark, the limb is still alive.  If it is brown the limb is dead and should be removed back to a point where you can find green living tissue.  Pruning will enhance fruit production in the spring.  After pruning, you should take a soil sample at the drip line of the trees.  It is probable that fertilizer may not have been added to the soil for a long time.  The soil test will tell you exactly how much nitrogen, phosphorus and potassium to add to the soil.  Contact your local County extension service for help with the soil test.  Finally, the lichens, although not harmful to the tree (many are used as indicators of air pollution, so you must have decent air quality to have them on your tree) can be sprayed with a copper sulfate product and they can be killed with several applications.  Bordeaux mixture is such a mixture and is organically approved and is non-harmful to almost everything except the lichens.  Let me know if this does not seem to be your problem and we can go in another direction.  Glad to help if I can.  Respond if this does not solve your problem.