Does not affect the fruit at all, except that the tree will produce less and less as it gets older and eventually dies.

This is information for control without chemicals Completely cut out all affected smaller branches and spurs. With the larger branches, try to cut out all infected material. All such pruning should remove all brown, infected bark and wood, cutting back to fresh green tissues. Paint immediately with a Medo, Prune and Seal or Arbrex Seal and Heal, to prevent the wounds becoming reinfected.

chemical control
Spray with the copper-containing fungicides Bordeaux mixture or Bayer Fruit and Vegetable Disease Control, once after picking but before leaf fall and a second time when about half the leaves have fallen.

the above is fron the Royal Horticultural Society Site

As far as I am aware it only effects the fruit at times and they will not fall - But I have had a tree with canker and the fruit was fine I sprayed mine - and it did recover