Plums have maggots

Hey there! My plums are magnificent but many of them have one maggot living inside, leaving brown trails (excrement i hear). I read that they leave the fruit end of summer and enter the soil, where they hibernate and become moths that come back in spring and lay eggs on the fruit.
Has anyone had any success in keeping these maggots out of the fruits?
I'm in Northern Germany, near Berlin.

Thank you!
Best
Lewis

Yeah, had the same with my plums a few years back, same brown trails inside the fruit. Sticky traps hung in the tree when it was in flower caught some of the adults before they could lay. Never eliminated it completely but it was noticeably better. Also read that loosening the soil underneath in autumn exposes the pupae to birds and frost, did that too and I think it helped. Worth a go before reaching for anything stronger.