Archive for the ‘Worms @ Work: Office Composting’ Category

Dealing with Compost Fruit Flies

October 18, 2010

Flickr / upyernoz

If you have a worm compost bin at work, you’ll likely have a fruit fly outbreak at some point. Your colleagues are going to hate it, and you’re going to feel bad because you’re the one that brought the worms and subsequent fruit flies into the office in the first place…

So, here are some suggestions for preventing fruit flies to begin with. And in case these don’t work, we’ve added a few tips below for how to deal with fruit flies that do emerge. We’re happy to report that all this advice has been field tested at Fairware with great success.


1. Don’t overfeed the binCity Farmer suggests adding food scraps to the bin once a week, placing the scraps in a different corner of the bin each time. A single feeding of the bin helps you keep track of how much you’re feeding the worms, which for a small bin like ours should be about 1L of waste per week. If you find that food scraps from the previous week haven’t been consumed, don’t add more. You want the waste consumed so fruit flies don’t lay their eggs in it.

2. Cover the food waste well – When you add the scraps to the bin ensure that the food is well covered by the upper straw/newspaper layer. Again, this helps prevent fruit flies from laying eggs in the waste.

3. Store up food waste in the fridge – Keep a receptacle in the fridge where you and your co-workers can store up food waste through the week. Fruit flies will attack anything left on the counter, even if it seems to be in a well-sealed container. Here’s a picture of the the Fairware worm food storage container:

Fairware's worm food collection

4. Chop up the food waste – Before feeding the food scraps to the worms, use a knife to cut it up in small pieces. This increases the surface area on which the worms can attack the food. Here’s an example of some of my fine chopping:

Food waste chopped into worm bite-size pieces

5. Stay away from citrus and banana peels or wash them well – Fruit flies love laying their eggs in fruit peels and sometimes they’re already in there before you place the peels in the bin. Rinsing peels before adding them to the bin can help prevent an outbreak.


1. Poison them – Here’s a recipe we’ve found effective (courtesy of City Farmer)

  • ½ cup fruit juice
  • 2 drops of vinegar
  • 2 drops of liquid dish soap
  • divide the mix between a few small cups and place them in areas where the fruit flies are found most

2. Cover the bin opening with a damp towel – By sealing off the opening of the bin for a day or so, we’ve found the fruit flies aren’t able to escape the bin and seem to die down in the process. But don’t leave the bin covered for more than a day or two, as it reduces the amount of air getting to the worms.

3. Stop feeding the bin for a while – Just stop putting food in it until the fruit flies disappear.


We’re still learning and are keen to find out new ideas for avoiding or dealing with fruit flies. Share your suggestions in the comments below.


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