Peach infestation

Hello! First time poster here. This years peach harvest is a disaster. Every single one of the 400 plus peaches are ruined! There are maggots/worms in them around the core and more aged fruit is soft and almost hollow.

We are on the sunny coast Queensland and the tree is 3 years old. Last year our harvest was amazing with none of these issues. The only difference is we sprayed a quassia chip mixture on them to deter possums. I suspect these little flies/wasps (see attached photo) and the peaches have this clear dried gel hanging out of them (other photo).

I realise this years harvest is spent, much to my kids disappointment, what can I do next year? What are these little buggers?

Cheers everyone!