I have dug a new garden bed a few weeks ago and planted numerous perennials divided from a neighbours garden (local plant sales are so wonderful!). I used top soil to infil (I am in an old clay quarry) & flower bed soil around the new plantings, as well as added a layer of leaf compost (commerically purchased) post-planting. (I have since learned it is good to mix it in before planting the new flower bed but leasson learned!). Anyways, I'm having massive fly issues and I assumed it was because of the compost but I've used this compost on another new garden bed (hostas) at the front of the house with no problem. We have a creeping shrub (not sure what it is) on the fence and it has recently flowered and the flies seem very attracted to the flower buds too, so I'm not sure if it's the compost, the flowers on the shrub, the type of plants or ??? My one cat has also taken to using it as a litter box (any suggestions on curbing that?) but I can't imagine that his amount of "output" could have attracted this many flies (and they are also not just in the area he's chosen to christen). Our neighbours have some flies on their side but not as many. Their side has fewer flowers and it's over their deck so there's no flower bed on that side. Would it help if I put a layer of mulch on top? Any suggestions would be greatly appreciated. Thanks! LSOD
If the problem is the compost you could try racking it in and watering it to help it decompose further. It its the flowers then there isn't much you can do. Either way they flies are harmless. If it's the compost then it will rot and there won't be anything for the larva to eat.
Since you used topsoil there would be no need to dig in the compost, which is also functioning as a mulch where it is now. To discourage cats in a bed cobbles or other material that is hard to dig through can be put over the top, as a mulch. The less like a litter box a spot is the less of a draw it will be for them. The shrub is Euonymus fortunei.