compost awareness week – swarms of fruit flies

Filed in Blog by on May 5, 2009 27 Comments
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compost for zero wasteThis week, in honour of one of our favourite zero waste pastimes; we’re celebrating Compost Awareness Week by answering some of your composting questions.

The lovely Madam Salami (who just happens to make gorgeous recycled, upcycled and precycled handcrafted items from unloved items – check out her store here) asked me about fruit flies.

Fruit flies in compost heaps are a common problem. They are not dangerous and won’t hurt you but it’s pretty unpleasant to get a face full of flies when all you’re trying to do is give your compost bin a decent meal.
Fruit flies do have their role to play in breaking down fruit and vegetable peelings; so don’t be too hard on them!

These little critters love humid conditions, so they tend to be prevalent during spring and early summer. They feed on the sweet sugars that fruit and vegetable peelings release as they are breaking down.

Here are three tips to reduce fruit flies in your compost heap:

1-    COVER!
Keep any stored fruit and vegetable peelings covered before adding to the compost heap. This reduces the risk of fruit flies getting in there and laying maggots before you’ve delivered your goods to the compost heap.

2-    CONSISTENCY!
Check the greens to browns ratio of your compost; as outlined in yesterday’s post. Fruit flies are often found in compost that is too wet. Check the consistency and add more browns (cardboard, paper, straw etc) if necessary.

3-    CONFUSE!
Every time you add fruit or vegetable peelings to your compost heap, cover with dried grass clippings or a brown such as shredded paper or cardboard to confuse the fruit flies.
An easy way to do this is to line your kitchen caddy with newspaper and wrap everything up before depositing in the compost heap.

As I said at the beginning, fruit flies are not harmful to you or the compost and the chances are, by the time you are ready to use your compost in the autumn, all the flies will have gone.

Just hold your breath when you take the top of your compost off; fruit flies can make you sneeze if you inhale them! (she speaks from experience)

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About the Author ()

I am a long time supporter of the Green and Sustainable lifestyle. After being caught in the Boscastle floods in 2004, our family begun a journey to respect and promote the importance of Earth's fragile ecosystem, that focussed on reducing waste. Inspired by the beauty and resourcefulness of this wonderful planet, I have published numerous magazine articles on green issues and the author of four books.

Comments (27)

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  1. John Costigane says:

    Hi Mrs Green,

    The closed kitchen caddy I now use has reduced fruit flies both in the composter and in the kitchen. The latter happened in a bucket / loose metal lid combination previously used. There still are some in the compost but this is a now minor issue.

    I have slugs in the composter as well as beneficial worms. My intention is to deal with slugs, using various means already mentioned in other topics.

  2. Sarah says:

    I don’t mind fruit flies really, same as I don’t mind the slugs, worms, beetles and other critters that use my compost as a home. I figure they’ll be food for something else eventually and they’re probably helping. Don’t want them in the house though!

  3. VegBoxClara says:

    Oh boy do we have fruit flies! I like the little blighters … And I like that I’ve created something that they like so much … But I take the point about the consistency, and I realised this morning that it’s so much easier to make sure I get my brown:green ratio balanced in the caddy than trying to do it in the main bin.

    Thanks!

  4. Madam Salami says:

    Fanblincintastic Mrs Green, thank you! Liking the lining the caddy with newspaper idea too. We share our compost bin with the inlaws who were totally confused by the whole notion so getting them to add a good mix of wet ‘n’ dry has been a bit of a struggle! Off to shread up some old bills to confuse my ever increasing swarm of fruit flies! (No lawn 🙁 so grass cuttings are impossible!)

  5. Poppy says:

    We had a problem with fruit flies when we first started composting and it did worry me I must admit, but we only get a few now, so no problem. DH thinks I’m barmy chucking all the kitchen roll and other paper and tissues in – guess I must be doing the right thing 🙂

  6. I always wrap my veg peelings in newspaper so am getting the proportions about right anyway.

    We have odd fruit flies, butnothing that we can’t cope with.

  7. just Gai says:

    When we bought our wormery from Bubble House we were given a small tub of white powder (I think it was lime?) to sprinkle over the compost once a month or so to get rid of the flies.

  8. Maureen says:

    I line my kitchen compost container with the brown paper bags that come with my organic fruit and veg from Slipstream Organics
    I just lift it out by the handles when it is full and bung it in the compost bin
    ps not had any fruit flies since I have put more paper and cardboard in the compost

  9. Mrs Green says:

    @John Costigane: Hi John, I think good preventative measures in the kitchen are important to try and stop the problem in the first place. I’ll be leaving the slugs in the compost – they are put to good use in there, imo!

    @Sarah: I’m with you on that, Sarah – everything in its place and all that. I like to co-operate as much as I can 🙂

    @VegBoxClara: Hi lovie, glad there was something useful in this for you. Let’s hope you see the problem sorted soon 🙂

    @Madam Salami: Glad it helped Madam Salami; it sounds like you are doing great with your inlaws! Good luck with the shredding and confusing!

    @Poppy: Sounds like you are doing things, perfectly, Poppy. It’s great that this has eased the number of fruit flies you are getting; and should inspire others to have a go!

    @maisie dalziel: Good to hear, Maisie; it seems if you get the ratios right, they are not a problem. We get quite a few here.

    @just Gai: Interesting; Just Gai – I’ll have to have a browse and see what I can find out about your magic powder!

    @Maureen: Good to hear, Maureen. So the consensus is that lining the caddy with paper can help to reduce fruit flies. Great news – I hope lots of people will sort this issue relatively simply then. Thanks for sharing your experiences with us 🙂

  10. Michelle says:

    Our newspapers get shredded and used as chicken bedding before heading for the compost bin. We only started doing it when we ran out of straw and needed an alternative until we could get some more. We never changed back as it worked so well. I am waiting for the full on fruit fly season to start before finding out if it reduces the fly population in our bin.

  11. Mrs Green says:

    @Michelle: Hi Michelle :)That’s a great reuse idea with the chickens bedding and it saves you the money on straw too. Let us know how the flies treat you this year!

  12. Sarah says:

    @Michelle: Now that’s a fabulous idea. We used to do that and stopped, and I can’t remember why…Possibly because we were using newspapers to make plant pots, but other shredded paper should be fine…

  13. Better to read the newspaper on line and take bags to the grocery store… Also high heat, thermal composting, breaks down WAY faster than using a tumbler type or trying to turn the compost. Using those methods cause you to have to fight fruit flies all year ’round. Using manure (animal or humanure) heats up the compost fast, breaks everything down fast, so fruit flies eggs are killed. And the best part is you never have to turn the compost! You just layer and watch it bake away!

  14. Mrs Green says:

    @Sarah: Funny how we stop doing these things, isn’t it Sarah. How many newspapers do you reckon you use to make pots? I used up all my cardboard toilet rolls tubes and would need to treble the amount I made for next year!

    @Millie Barnes: Hello Millie – good to see you and thank you for leaving a comment. Hot composting is great if you have the facilities to do it. For many people in the Uk, with their little patches of garden, this isn’t an option, so lots of us do the cold composting method.
    Like you say, hot composting is much better and faster, but not practical for many.
    Thanks for sharing your tips for those who do have facilities and space to do it – you sound like a pro!

  15. Williemakit says:

    I’ve got an idea for turning a mass of compost inside a bin. Those of us who use bins know what a pain this can be without a compost agitator. I have a heavy-duty 1/2 inch drill and an agitator that I use to stir drywall mud. Has anyone tried this? If so does it work. I would start by using a compost aerator and water to soften things up a bit, or I’ll bet I’d wind up giving the old shoulders and elbows a good twisting. I guess the best thing to do is go ahead and use it and evaluate the results if I get no replies here.

  16. Williemakit says:

    Further to this, I doubt any fruit flies, maggots, or flies/maggots of any type are going to enjoy this ride!

  17. Mrs Green says:

    @Williemakit: Hi Williemakit; welcome to the site and thanks for your comments.
    It’s not something I have tried; so please do go ahead and let us know if it is successful!
    I’ve been eyeing up a tumbling composter; these seem like a great idea and you can buy them without air vents, so flies shouldn’t be too much of a problem.

    Good luck with your idea!

  18. Martha H says:

    We have fruit flies in our kitchen caddy and around the kitchen. I am ok with the flies outside, but inside it’s a pain. Not sure what we can do about this. The flies seem to be laying their eggs on the filters in the caddy. Anyone have any ideas?

  19. Mrs Green says:

    @Martha H: Hi Martha, welcome to the site. For flies inside, you need to do virtually the same as outside. Ensure your caddy is well sealed; keeping it sealed apart from when you add something new, and wrap stuff in newspaper before putting it into the caddy.
    If you have something mouldy to put into the compost, I would take it straight to the compost heap rather than store it in the caddy. And in hot weather, empty the caddy every day; in cooler weather 3 days might be ok.
    HTH

  20. Diz says:

    my compost isn’t working! I started it January 09, and took a peek a few weeks ago – it’s all looking very recognisable at the bottom! I tend to line the kitchen caddy with newspaper, and empty my shredder in there. At one point I did have worms dripping off the lid, but all I have now are fruitflies in the top (a lot of stuff had been emptied in there and not covered with brown) and woodlice in the bottom, as far as I can see.

  21. Sarah says:

    @Diz: Your balance is wrong somewhere – is it too wet? too dry? When mine goes like that I stir it up and then water it and that seems to kick it into working. If your shredded paper is clogging it up you might want to find more green stuff to add in too.

  22. Poppy says:

    When our first small bin went stale, i was advised to get the men of the house to errrm, water it (if you catch my drift!!

  23. Mrs Green says:

    @Diz: I second Sarah’s advise; stir it up and have a look at the texture. You’ll looking for a well wrung sponge. If you grab a handful of the mix from the middle of the pile you should just be able to squeeze a drop of water if you squeeze hard. If it’s too dry add some greens such as grass clippings or veg peelings and if it’s too wet, mix in some more shredded paper or card.
    Woodlice are ok in there 🙂 They’ll eat through the brown stuff.

    @Poppy: Poppy, that is a great way to get the bin going. Diz, you could add some nettles, comfrey or man wee to it to get it going once you’ve mixed it up

  24. Sarah says:

    @Diz: Diz, do you have some comfrey growing? Asuming you’re in the UK I can send you a root if you like?

  25. Bea says:

    We used our organic compost for our peace lily. It now has fruit flies by the swarm. No amount of chemicals or effort will get rid of them and if we put it outside it will die! Any advice on how we can fix this without killing the plant. Thank you.

  26. Ben says:

    @Bea: Fruit flies like the damp surface of the soil, so watering from below and allowing the surface to dry out will help get rid of them. A bit of fly paper nearby will also help collect them. However, I’ve also had good luck with house plant pesticides the couple of times I got them in the house plants, so not sure why they’re not working for you. How long has it been since you applied it?

  27. Mrs Green says:

    @Bea: Hi Bea, I know Ben is taking care of you with your query, but just wanted to welcome you to the site 🙂

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