My worm composting bin is infested with fruit flies. What can be done to get rid of the flies?
Generally this comes from having an excess of "greens" rather than "browns" in the bin, and potentially too much moisture also.
When this has happened to me I generally put a generous amount of shredded newspaper / junk mail in, and try to let it dry out as much as possible - the fruit flies will then tend to up and leave.
It's probably also worth noting that the flies aren't an inherent problem to the compost per-se, they're just rather unpleasant.
You can make a trap to catch the existing fruit flies with an empty jar, a small plastic sandwich or zip close baggie with square corners, a rubber band and some wine or beer.
Pour a small amount of beer in the bottom of the jar. Snip off a tiny bit of the corner of the bag, making a small hole. Push the corner of the bag a few inches down into jar, making a funnel shape, and pull the rest of the bag over edge of the jar. Put a rubber band around the the rim of the jar sealing the edge of the bag.
The fruit flies crawl in through the funnel, then can't get back out. I seen similar versions of a fruit fly trap where you punch small holes through the lid of the jar with a nail.
I will make this brief: Search for fruit fly lifespan. An associated article shows an experiment of the effects of sweeteners on fruit flies done by a 6th grader. He found that Truvia killed fruit flies. So I tried Truvia in my worm bin and it works! AND the worms are not harmed. You should try it and if it works for you, spread the word: No more fruit flies in worm bins. Steven Goddard
The combination of 4 things worked for me:
- stop over-feeding and let the compost dry if too wet
- vacuum the flies daily
- cover all the food scraps and put a layer of dry newspaper shred on top of the compost
- have a trap near the compost to catch some of the flies (yellow container with water + dish soap + sugar works for me, as yellow color and sugar attract flies and dish soap makes them drown)
This method instantly improves your compost situation, but it may take weeks to get rid of all the flies, as your compost probably has some eggs.
As others already said:
- add more dry stuff to reduce the moisture (cardboard pieces),
- open it daily to make the adults fly away,
- use a vinegar bait and cover well all the food with dry material (cardboard pieces).
- kill the pupae (cocoon) that you see on the back cover or box walls, they are the fly cocoons which looks for dryer part of the compost to become adults.
- stop putting in fruit remains. Put only non-sweet waste (vegetable)
In practice: my personal experience is that if you keep in putting fruit waste, fly larvae will keep managing to grow and you won't manage to get rid of them entirely.