Question
I have a newly planted Higan Cherry tree in mid Wisconsin.
I recently noticed a strange blackish, tar like substance on the branches in a few different spots. It was very hard, and wrapped around the branch. About an inch long.
I cut the branches off that it appeared on.
I am noticing some leaves yellowing and some with small holes in the leaves.
I can't see any bugs on it to cause the holes.
I fear the tree is in danger.
I have it planted on a very warm sunny west side of the house.
I appreciate any advice.

Answer
The black is Black Knot disease.  Black knot of plums and cherries is a widespread and serious disease throughout the United States. Black knot is a common disease  on wild plums and cherries and in home orchards where pruning and spraying are not regularly practiced.

The disease becomes progressively worse during each growing season and unless effective control measures are taken, it can stunt or kill the tree. The black knot fungus can infect American, European, and Japanese varieties of cultivated plums and prunes. Sweet, tart, and Mahaleb cherries are also affected by the fungus, but are generally less susceptible than plum or prune. Occasionally, it may also infect apricots, peaches and other Prunus species.

Established orchards or backyard trees should be scouted or examined each year for the presence of black knot, and infected twigs should be pruned out and destroyed or removed before bud break. If pruning is not possible because knots are present on major scaffold limbs or the trunk, they can be removed by cutting away the diseased tissue down to healthy wood and out at least 1/2 inch (1 cm) beyond the edge of the knot.
 
Fungicides can offer significant protection against black knot, but are unlikely to be effective if pruning and sanitation are ignored. The timing of fungicide sprays should be adjusted to account for inoculum levels and weather conditions. Where inoculum is high because of an established black knot problem or a neighboring abandoned orchard, protection may be needed from bud break until early summer. Where inoculum has been maintained at low to moderate levels, sprays are most likely to be useful from white bud through shuck split (the period of maximum availability of ascospores). Fungicides are most necessary and will provide the greatest benefit if applied before rainy periods, particularly when temperatures are greater than 55 degrees F (13 degrees C). In evaluating control programs, remember that knots often do not become apparent until the year following infection. Captan is the primary fungicide found in home fruit spray mixtures (Multi-Purpose fruit sprays) such as Fruit Guard, Home Orchard Spray, Fruit Tree Spray, etc. It can also be purchased separately as Captan or Othocide.

The leaf problem from the description I can not ID.