Apple twig cutter
We have a young dessert apple (Sunset) that is being attacked by an unknown pest. The growing tips are being cut 2-3" down from the tip. They are severed cleanly about 90% across, and they then flop over. The tree is therefore not growing up but producing lower side shoots. It is in uncultivated ground.
It sounds as if the problem is being caused by the apple twig cutter Rhynchites caeruleus. This weevil attacks apple and other fruit trees, partially severing new shoots about 3 inches or so from the tips, so they hang off as yours do, or drop to the ground.
The adult lays eggs in the shoot tips from early June (they are more active in warm, sunny weather), the eggs hatch and the larvae munch in the pith of the shoots for about three or four weeks, before dropping to the soil to pupate. New adults emerge in late summer then hibernate under dead leaves or other sheltered situations. As soon as you see signs of damage, trim back the affected shoots and take all trimmings to the nearest green waste site. This way you'll break the cycle.
Damage is rarely serious although young trees can be more susceptible. In winter, cultivate under trees, and clear out hedge bottoms to expose overwintering adults. To improve the growing conditions of the tree, clear an area of at least one metre square around the tree trunk, and keep this free of competitive growth.