A question about plums

Hi,

I have a victoria plum tree which gives us lots of fruit most years, but this year some of the fruits had maggots in them. There was no sign on the outside of the plums so I assume something got in at the pollonation stage. 

Has anyone experienced this and how do you stop it happening (organically if possible)?

I assume it was a moth of some kind

Thanks for the link 'Ice' It says to use 'Derris' spray on the flowers, I,ve googled this and apparently it has been withdrawn because of links to Parkinsons Disease

Is there an alternative organic spray?

Thanks, I will have a good look when the flowers are falling.  Sounds like a painstaking task but better than having a mouthfull of maggot