I seem to be needing to prune constantly, with the trees always springing, spouting and suckering. But I guess that is good, as it tells me the tree is alive!
Pruning your fruit trees in summer is vital to discourages vigorous growth, so you can keep it to a comfortable height, which is whatever height you can easily pick the fruit at and put netting over.
Pruning apples and pears at this time may encourage fruit spurs. Prune back the vertical growth, 2 or 3 buds up from its connecting branch, and cut under the bud above, and then maybe those left will turn into fruit spurs and flower rather than sucker up.
When pruning, think of an open vase shape, which is very popular as it is easy to manage and healthy, allowing plenty of air and light to get to the centre of the tree, as well as enabling you to get in and pick the fruit. You are looking for 4 main branches and need to prune to about 30cm below where you want the optimum height to be. At that point cut to an outward facing bud. Also prune anything growing inwards, broken or diseased.
Other times to prune are in later winter, if the tree is young, to encourage growth and allow you to shape it, and also after the fruit is picked.
Finally, for now that is, thank you Catherine from Burradoo NSW, who has sent me this photo of the tree frame she built, which stood up to 100+KM winds recently AND left her with enough plums to make 30 jars of jam!