We have a pembina plum tree that has plums on it however as the plums grow they expand (swell) to be about 3 cm. or so. They are hallow inside and they shrivel a little. A few of the plums, very few are normal size, dark green and hard. The neighbour across the fence has the same problem. I can not find an insect or pest on the tree or in the fruit when I cut it open. This is the second year this has happened but we have had three good crops of plums other years.
