Hi Shirley, I would recommend reaching out to the state plant pathologist, Todd Steinlage, to see if recognizes this and has recommendations. It doesn't appear to be insect-feeding damage to me, it's possible it could be some kind of pathogen, or possibly just sort of typical late-season decay now that we've had so much rain. His email is <personal data hidden>

Since this tree was just planted too it likely is a bit stressed trying to get itself established. Stress on trees can cause premature leaf senescence and also can make a tree more susceptible to insect and pathogen issues. Making sure the tree is watered during dry spells, is planted in a location that meets its needs, and being careful not to compact the soil too much or accidentally damage the tree with lawn equipment can help reduce stress on the tree.

You can find more information about tree planting and care at our website here: https://www.uaf.edu/ces/publications/database/gardening/plant-a-tree.php