Question
QUESTION: Hello, I am puzzled about a preponderance of tiny (pinhead or pinpoint sized lesion/nodules covering the majority of our Maple trees (plural) leaves - I believe the trees to be Crimson Kings, but will not bet my life on it. The lesion/nodules are a bright red to brownish red shade with a yellowish green margin. They are often in tight clusters, but also appear a single spot. The placement of the lesions/nodules on the leaf is random, some appear on the margins while the majority will be scattered over the entire leaf surface.

I have been trying to find some resource to help with the identification of the these to understand if I need to worry about other trees in the vicinity acquiring this unsightly blight.

Thank you for any insight you might be able to share.

ANSWER: Sounds like you are describing and insect gall.  Many insects will cause small galls on plants as the larvae of the adult pupates inside.  You can try to cut one open and see if there is a bug inside or if there is an empty cavity inside.  If you see this, then I would say the insect is the cause.  They probablt wont cause much harm but will make the tree unsightly.  If you wish to treat for the bug,  I would treat the plant with Bayer Advanced Tree and Shrub Insecticide.  This product is mixed with water and poured on the soil around the base of the plant.  It is taken up systemically and will kill the bugs within a week or so.  It also provides protection from reinfestation for up to a year.  I hope this fixes the problem.  Good Luck.

---------- FOLLOW-UP ----------

QUESTION: Thank you for your insight. All the lesions/nodules appear to be empty bumps on the leaves, but I do not have a microscope to determine if this is the reality.

These two trees are surrounded by cedars, firs and spruces. What is the likehood of this 'insect' migrating to any of these trees? Woodpeckers have been feasting on the two maples - I am thinking it is time form them to come down. I am concerned about any further spread of this infestation.

Answer
The insects will go to other dicot type trees such as birch and oak but probably will not affect the gymnosperms (cedars, spruces, firs, etc.).  Woodpeckers will pick on Maples and single them out.  The woodpeckers are most likely protected species.  The will not kill them however, just leave the holes in the trunks.  I would try the insecticide I recommended for at least one year and see if it controls the bugs, then make your decision to cut the trees down.  You may find the product works good and everything will be OK.  If it doesnt, sharpen up the chainsaw.  Good Luck.