If there is one thing that makes my eyes cross, it's Queensland fruit fly. My nemesis.
Our fruit trees are seven years old, and in that time, we have tried all sorts of things to stop these little pests in their tracks. This year, we are going the belt-and-braces method. ie. we are throwing everything at these trees that we can. So, here is a Japanese plum (can't remember the variety - Mariposa perhaps?) It is covered with small developing fruit. Firstly, we had the trees pruned in winter so that the tree is a manageable size so that we can use exclusion bags effectively. Secondly, I've hung a fruit fly trap, seen here dangling on the left. The mixture in the trap consists of warm water, sugar, vegemite, vanilla and urine. I'll let you join the dots on my devotion to this task yourself. Thirdly, I've been spraying the tree with spinosad (an organic compound), and will keep this up weekly until harvest around Christmas.
Action Man reckons we should spray with nasty chemicals as a last resort. My thinking is that if we do this, we may as well buy our fruit. Heaven knows, it will probably be cheaper.
If all this fails, and we still don't get to eat any fruit this year, but are sending bags of rotting fruit to the tip, the next step is a chainsaw.
I think the problem is our insistence on growing stone fruit in an area where fruit fly is endemic. Sometimes retreat is the best way forward.