Question
Is it too late in the year to apply manganese sulfate (29% total manganese) to a Red Maple or is next spring better?  I intend to drill 8" deep holes around drip line and apply dry using 1/4 pound of product (tree is about 50' diameter).

Answer
I would wait until next spring that way the roots as they absorb the manganese will transport it to the leaves. If you do it the trees has just about shut down for the winter and very little minerals and water is being transported from the root to the leaves.

It maybe that the soil ph is too low and the manganese is tied up and is not available to the tree. Need to have the ph tested and get it near 7.0. Here is a web link for more information on how to do this.

http://www.ext.colostate.edu/pubs/garden/07727.html