Apple trees and water shoots/epicormic growth
I have been having an ongoing discussion with a coworker regarding the correct method in addressing water shoots or epicormic growth on apples. My training with pruning these trees included the recommendation to remove water shoots or vigorous epicormic growth as soon as it appears, as it tends to sap vigor and seldom can be coverted to a productive, fruiting structure. I was also informed that heavy pruning during dormancy would result in a strong epicormic response the following season and that pruning in summer would reduce this response.
My coworker - educated in another pary of the country - seems to think that maintaining a significant portion of epicormic growth has a profound effect on fruit production and ripening. If you remove all (or most), fruit production will be reduced and ripening will be serious delayed.
I can find no literature to support this contention. What say the experts? Does epicormic growth serve a useful function in fruiting and how should it be addressed?