On espaliers we do much summer pruning to, a) control the vegetative growth, b) maintain the shape of the espalier and c) to encourage the formation of fruiting buds/spurs.
So my questions are:
Do we have any research that tells us at what point in the season is the “determination” made as to whether the growth will be a fruiting or vegetative bud?
Usually terminal buds and next years fruit bud formation gets going after harvest. With my atrocious (0%-1% of normal) fruit set this year, many trees will have NO harvest. Can I expect this to occur earlier? There will be plenty of “energy” to go into other than fruit development.
The attached document might answer some of your questions. It covers all factors that effect fruiting and flower formation.
Here is an excerpt for when flower initiation begins, flower initiation being defined as: The time when the meristem is committed to form a flower. Usually occurs early during active vegetative growth. There are no visual clues to this development