@Darren based on where you are I’m not aware of a fly that should cause any real problems. Also, before ripening, the plant is full of so much latex that it puts off many bugs. Not all unfortunately. I’ve had Japanese beetles eat up leaves. Borers like ambrosia beetles usually only attack damaged and decaying wood. The time when protection becomes really important is when you start to have near ripe figs on the tree. Then the insects come… and once they know where the goodies are… they bring their friends
When you get closer to harvest keep a close watch out for wasps, ants, earwigs and the dreaded Asian lady beetle. They look very similar to ladybugs but they love figs.
Many of us here are heavily invested in this type of organza bag. When the figs begin to take on a good size we slip them on as we walk the trees. They don’t help much with raccoons but they do a very decent job of protecting from bugs and even birds
I have a very aggressive type of paper wasp here that will try and chew through the bags if the fig is up against it. I try to set it on so the fig doesn’t touch the bag wall.