Unidentified cherry pest
I have a mature sweet cherry tree which produces large amounts of fruit every year but this year I am having to discard at least half of the fruit as it has been attacked by a pest I have not come across before. The symptoms are a pinprick size hole in the cherry which after a couple of days causes the surrounding area to turn brown with eventual rotting. I have tried cutting a few open but there is nothing that is apparent to the naked eye. I am sure it is coincidental but every other year multitudes of blackbirds, starlings and wood pigeons descend on the tree but they are almost totally absent this year, it is almost that they know there is something wrong with the fruit.
Can anyone suggest what is causing this?