Not easy. Some things to try, but all basically cut down the numbers as opposed to an instant cure.

- Smaller feedings, or give them a break from feeding altogether (have bedding they can munch on though). Also freeze (then thaw) feedings before adding so they get processed faster. Worst thing is food hanging around for weeks.
- Bury the feedings under some VC. Doesn't have to be that deep as long as it covers everything, just don't want it open air. Loose shirt might not work unless it's really tight, loosely on top doesn't really count as if there's any gaps they can crawl in easily.
- If they are coming from the top tray, try a mesh lid. Fine mesh overtop instead of the plastic one, held in place with bungie cord. Seals better than the plastic lid (at least the lids I've seen). Also stops the wife from seeing them flying around :). You can then lift up a corner and stick a vacuum inside without letting them all out (as the plastic lid would). Tap it around a bit to get the suckers to fly up and into the vacuum of death. You can do that daily to make sure they don't get old enough to lay more eggs.

With time you can drastically reduce the numbers flying around.

Great suggestions thanks!! The big fly explosion came after a particularly large feeding. Also I haven't been good about covering the feedings I figured the shirt was good but perhaps not. I've seen a hemp worm blanket is that worth a try or just a waste of money?

Can't say really as I haven't tried it myself. If it's a tight weave but still allows air through and not expensive can be worth a try. Just tuck in the sides or something. Anything loose will have the flies fly right past, they are pros at that.

If they are fungus gnats, Peter is right on the money. If they are fruit flies, Peter is still right but you may also want to try a vinegar trap. Basically, fill a cup about 2/3 with vinegar, add one drop of dishwashing liquid (to break the surface tension) and place the cup near the bin. If, after a few days there are several dead flies in it, then you have a fruit fly problem. Fruit flies are relatively easy to get rid of, fungus gnats, not so much.

If you have an empty long neck bottle of some kind put some vinegar in it don't need but about a half cup and set it near the bin. the flies get in and drown. You can also use a bowl or wide mouth jar covered with plastic and a few holes poked in it. You will have to change the vinegar every other day or so. This worked for me. Vonnie

I've found banana peels in a bowl, add an inch or so of water and a few drops of dish soap, cover with plastic wrap with rubber band then poke some holes in it, works quite well.

I have an outdoor bin, but when I had a fly problem in it I used an old-fashioned fly strip. Because it is so long, I attached both ends of it to the lid (making a 'U' shape) and it cleared up the problem very effectively.