[Annie]

It probably crops bienially due to the humungus crop,your little tree needed time to recover!If you thin the fruit out a bit this year then it may fruit again next year.Some trees just seem to fall into this pattern though but worth a try.
We would have to have cut our tree down if we`d followed the cut and burn advice too and since it was obviously a long standing disease and the apples and blossom beautiful we had nothing to loose.I do clean my secateurs though after cutting out bad bits just to avoid spread.

[theappleman]

What you describe, Sweet Nasturtium, are probably burrknots. These are root primordia which appear on shoots in wet climates on some varieties. This is common in old Welsh types such as Pig Aderyn, Pig yr Wydd, Pen Caled etc and on rootstocks themselves. They do no harm.

These old varieties were propagated by cuttings, a branch containing burrknots being cut off and driven into the ground where it soon rooted.

Canker spots are oyster shaped, sunken and reddish brown though they can heal over in time. These can be tidied up with a knife during the winter and badly affected branches cut out and burned.

Hope this helps.