How do I get rid of this plague of compost flies?
I have a fair selection of plants around the house, and while I'm far from being an expert, they do generally seem in pretty good shape.
However, I seem to have a plague of small black flies that live in and around the plants. I was told that these are compost flies, and like warm damp conditions, such as the soil of house plants. Unfortunately, they are a serious pest in the house as they get everywhere, and I would like to get rid of them. The plants don't seem bothered by them, but the occupants of the house sure are!
I tried various things, including spraying with baby Bio bug killer designed for such pests, as well as pouring very soapy water into the compost. Apparently this latter method is supposed to kill the flies without killing the plant.
In both cases, there was a temporary reduction in the number of flies, but only for a day or two. Sooner or later, they were back in force.
Anyone any suggestions as to what I can do? I don't want to get rid of the plants, but I can't live with all these flies. I don't see how I can keep the plants any cooler, as they are all indoor plants, and in a centrally heated house, they are bound to be in a warm environment (they'd probably die if it were cold anyway). I also don't see how I can keep them any less damp, as I only water the plants once a week (except for a fairly large Coleus, which droops if it isn't watered twice a week). I certainly don't over-water them.
Thanks in advance for any help or advice you can give.