Have you tried freezing your food scraps before adding them to the worm bin? That doesn't help much now, but it could help reduce future populations by killing the eggs.

It sounds like you have done the vinegar traps--bowls of vinegar with cling wrap over it and toothpick holes in the wrap.

What a pain. I hope this problem gets solved quickly!

Some people have success using sticky no-pest strips.

Not sure what type of bin you have, but I would stuff the top completely with bedding. Cram it in. Make the flies work hard to get to the food. More is better. Pull it back when you feed, then replace it.

I use newspaper flat on the top of the bin and even tuck it in when I get an invasion of fruit flies. Works for me, give it a try

Last time I had an invasion of fruit flies, I covered the top with tulle , and used string to keep it in place. When it was time to feed my herd, I would carry the top section (I have a COW) outside to set the adult fruit flies free :) In no time they had all hatched and been released into the wild. Freezing the food to kill any eggs never worked for me.

I had to resort to bug spray and no pest strips. They both will do the job, but they do release chemicals into the air that you may not want near food or where you spend a lot of time.

I used sticky traps to cover the holes in the netting the mouse chewed on the worm in. The traps became covered in the fruit flies that could now escape. Fruit flies seem to want to fly up only. The fruit flies seem to want to land right above the bin. I can see how they would land on fly paper dangling. That must be quite a site after a few months. I know the sticky trays were fully covered. Time for me to get new ones. If using netting just put the food in the bin under the cover. The flies do not try to get out. I should probably only feed when the fruit fly population is at zero and it is safe to open the net.

Thanks to everyone for your helpful responses to my fruit fly problem. The solution turned out to be 2 things. One...I covered the beds with sheets of newspaper and tucked it in on all sides. That has them under control in the worm bin. Thanks Mooshy. You are a doll. Yes to the question of freezing scraps, but I add chick starter to my feeding. The worms LOVE LOVE LOVE it. And its only 89 cents a pound. Make sure the chick food is not laced with any additives. It will kill the worms. Baby worms love the chick food and do well with it. Just soak it in water and then make sure you mix with your slurry of veggies to keep the protein content in check. I am not paying these ridiculous prices on Ebay and Amazon for worm food. Second....since the respiratory system of fruit flies is very delicate I discovered "Endust". You know...the stuff we use for dusting. I nail the buggers when they land on something outside the bid, or on the wall. Never spraying over top of my bin. Cough cough..choke and die. The oils remain and future flies land in it and die. Then I just get a dust rag out and polish up.

Glad to hear you have it under control. Not much in the worm bin seems to bother me more than when fruit flies are buzzing around my head. :)

Glad you got the fly situation under control. That can be a real pain. Last year I was having a small similar problem.

How I remedied it was use some dummy pots with moist soil and sticky cards . I also put some bonide insect control in it . I set these pots near the bins and in a short period of time problem solved . Since then Ive had no problem and but I try to keep plenty of shredded paper in the bins to the top

Keeping your worm bin outside eliminates the urgency to keep natural breakdown creatures out of it while allowing for a worry-free large bin.

If you are not ready to do that yet, a push-button ignition blowtorch will allow you to surprise the flies, wave the torch around a few times, and zap the wings off of dozens of them at a time. This will get the beneficial saprophagous insects out of the way so you can get more of that wonderful anaerobic scent going.

If you leave them be, you may notice an increase in predators that will breed and help out in the garden, but only if you put your worm bin outside where everyone can be happy.