Cherries

I have been growing cherries for over 25 years and never once had trouble with pests. Oh dear this year there is a major problem, and it is affecting dessert and Morello varieties. The fruit is turning black at the base and is soft, and on picking there are little white maggots coming from them and tiny little black flies. Anyone know the cause and how to prevent it next year. We grow organically so don't want to use chemicals. I fear most of my crop is ruined for this year as the trees are adorned with fruit as usual  - so gutted!