Montmorency doesn't need a pollinator. It should set fine by itself. Perhaps some of your fruit was frozen.

Thanks fruitnut, but my fruit was never frozen (my city never suffered from the nasty spring freezes), and I know it is a self pollinator. Just thought there might be another answer. Thanks, Mrs. G.

You still need bees- I don't believe they can set fruit parthenocarpically. Maybe the weather cut off pollination.

Another possibility- I'm seeing a very light crop on apples that weren't frozen for reasons I can only speculate about. A spring that starts off very warm and clear and then has a long period of grey cool weather, as we've had, can deprive trees of adequate energy to hold onto fruit. They rely on stored energy to leaf out, flower and begin fruit, if they use that up and leaves don't get enough direct sunlight and warmth they may abandon fruit to protect their wood and leaves, I believe.

Last summers monsoon may have even left trees with less stored energy than usual.

H-Man you've got something there. Last summer, this past winter, and spring were all so confusing to us, it must be confusing to the trees as well. Bees are always a problem here. I have so many flowers planted around my orchard, but we have so few bees. They were fine for about two weeks in April, and now they are gone. There are a few bumbles around but not making a difference. Bees love my crabapple trees but don't make it down to the orchard.