The other day I noticed these small (~1/4" dia.) swellings on some of the 1yr apple trees in my nursery. I did not see any on nearby pear or prunus trees. I cut one of the swellings through and it has a small black spot inside, I assume dead tissue. Some of the swellings had a scabby spot or crack in the middle. I live in central southern Ontario. Any help in identifying this appreciated!