I am visiting my son and noticed a new tree in his back yard doesn't look...
Is this a maple tree and is this just an unusual leaf which is missing a lobe?
From the photo, it does look like it has a leaf spot disease, but that is not troubling in and of itself, especially during this wet year. Do you have any other photos which show more of the tree canopy? They could be attached to your response here.
If the tree is newly planted, be on the lookout for problems with it's installation, for instance the cage or burlap was not removed or it was planted too deeply or mulched too deeply. Has it been watered regularly when needed? All of these factors can lead to a failure to thrive, but the leave alone doesn't look terribly concerning.
We see that many of the trees in the background of the photo are dead and your son's deciduous tree and several others of the same species (a type of maple) have poor leaf color and are not thriving. This suggests that the problem is environmental, possibly having to do with how the trees were installed.
We cannot see the tree's flare at the base of the trunk and suspect that it was planted too deeply when install, and also it may have been planted too deeply in it's container in the nursery. At any rate, your son should pull away the mulch and expose the tree's flare. This may require removing some soil at the base of the tree.
Also, mulch should never contact the trunk of a tree and should be no more than about 2" deep. Keep the mulch off the trunk. It leads to disease and insect problems.
Half of tree problems are not related to insects or disease, but are "environmental." Please read over the following fact sheet about abiotic plant problems and see if any of the others listed apply to your maple: http://extension.umd.edu/learn/common-abiotic-plant-problems-hg86