Does Freezing Kill Fruit Flies?

A small bag ‘o’ rotten fruit scraps (containing fruit fly larvae and/or eggs) ready for freezing

Not too long ago, one of our regular readers, George, shared a really interesting (and surprising) tidbit of info about fruit flies. In a nutshell, he has found that these annoying pests seem to be able to survive freezing temperatures!

Given the fact that I recommend freezing fruit/veggie wastes as a means of ensuring the materials are free of viable fruit fly eggs/larvae, and have had (blind?) faith in this approach in general, I knew this was something I needed to look into!

SO, I’ve decided to start with a simple experiment, and then will expand from there as needed. Today I obtained several pieces of well-rotted fruit waste (an apple core, a piece of cantaloupe, and a piece of watermelon) from a section of outdoor worm bed has a lot of fruit flies associated with it. I feel pretty confident, then, that these materials will have at least some fruit fly eggs and larvae.

All I did with the pieces of fruit waste was put them in a small ziplock bag and toss them in my deep freezer. In a few days I will remove the bag and empty the contents into some sort of small container. I will let everything sit for a few days (indoors at room temperature) to see if any fruit flies appear. It will of course be important to make sure there is no chance of fruit flies getting in to the container. I do seem to have a few of them buzzing around in my kitchen and basement, so some extra precautions will certainly be warranted.

If I don’t see any fruit flies hatching out from the materials I will repeat the experiment, but will make absolutely sure there are fruit flies to begin with (by letting some fruit/veggie waste sit exposed in a small container outside until there are clouds of them in the container). If it does seem like fruit flies have hatched out from the frozen material, I will also repeat the experiment just to make sure.

Thanks, George, for the inspiration!
Should be interesting.

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    • Boston Pinay
    • September 8, 2010

    Good luck with the experiment! Even if freezing doesn’t kill off the critters, at least I’ll get more room in my freezer back.

    It’ll be good news either way. 😀

    • Ted
    • September 8, 2010

    I take one extra step and it has been pretty successful.
    I put my fresh fruit and veg scaps in a opened zip lock bag. I then zap it in the micro till steaming, let it cool down then into the freezer. Being a cook, the only bacteria that can protect itself from freezing or even a deep fry, is Staphylococcus Aureus, (Staph Bacteria). I don’t think theres anything in the bugs world that can withstand being cooked, then frozen.

  1. I pick up rotten apples and pears off the ground, froze them overnight, thawed them out, and added them to my bin. No flies, gnats, bats, or rats.

    • jean kruse
    • September 8, 2010

    Back when I had a fruit fly invasion in my kitchen I put some bananas in the micro to keep them away from the flies. When I took them out I noticed a lot of fruit flies had followed the bananas into the micro so I quickly closed the door and zapped them for a minute. They flew out apparently unharmed so all I probably did was create a super new mutant of fruit fly. I’ve done this more than once just to make sure I wasn’t seeing things.

    • Bentley
    • September 9, 2010

    “No flies, gnats, bats, or rats.”

    JEAN – that is NUTS! Teenage mutant ninja fruit flies! Scary thought!

  2. In Hawaii, you can be sure there are fruit flies in some of your peels. When I freeze, I don’t have problems. When I don’t freeze I do have problems. I also have to have about 6 inches of dry bedding (machine shredded newspaper all crinkled up) to keep them out so they don’t breed in the bin. That combo has been successful in my studio apartment for years.

    The local expert says fruit flies deposit eggs on the surface of things and won’t go digging down through bedding to get to the food. That’s my experience! Freezing may not kill 100% of the eggs, but it kills enough. I also freeze until the food is frozen completely through. Not because I’m trying to do that but because I don’t get around to feeding the boys-and-girls that often. I still occasionally get fungus gnats, but I don’t have the same level of loathing for them as I do for fruit flies.

    • Kator
    • September 10, 2010

    I have a ton .. well .. so far a half dozen .. bagged milk cartons stuffed with fruit/veggies in my basement upright freezer (wife has only restricted my space to one shelf so lots of room left for more). I like Bentley’s thinking about freezing. I read that slow freezing really breaks down cell enzymes through formation of ice crystals, while quick freezing retains greater integrity of cell enzymes. However, my primary interest is to kill the fruit fly and I’m also eagerly looking forward to the results of this experiment. ??

    • Kator
    • September 10, 2010

    ooops ??= 🙂

    • Kator
    • September 10, 2010

    Oops .. ?? = 🙂

    • harlene geier
    • September 11, 2010

    hey guys,

    I also freeze my fruit scraps, (bananas & apples from co-workers) for a few days before I feed them to my babies, uh I mean worms. I still have a few fruit flys?, I think they’re nats ( they’re SO small) around my bin every once in a while. The way I get rid of them is to take my bin outside & put it on my porch for a few hours when I notice their numbers building up, or during feeding time.
    I have thought of another way to kill the little buggers, I fill a glass half way with water & add a few drops of dish liquid to it & set it next to my bins, they usually end up drowning.

    Happy worming,


    • Kator
    • September 17, 2010

    Hey Bentley: Curious to know how this experiment turned out. If you’re satisfied that it’s totally effective, then I intend to continue to freeze all fruit/veggie material before processing. If not, then I’ll only freeze surplus material. Thanks 🙂

    • Christina
    • February 11, 2011

    Here they seem to say that fruit fly eggs are extremely sensitive to freezing and that until 1990 scientists weren’t even able to figure out how to freeze them without killing them.

    • Jane
    • October 14, 2013

    I keep a container under the sink that is thick with fruit fly larvae and eggs. Today I took it to the chest freezer. Hopefully by tomorrow I will be rid of the fruit flys under the sink but I am breeding another batch in the worm room. The eggs are thick on the worm tower lids. I have recently moved to N/W Indiana from Michigan. I had a fruit fly problem there but controlled them with fly paper. I have never noticed the larvae before. The problem seemed to lessen as the weather got cooler in Michigan. Hopefully that will happen down here too.

    • Quitlan
    • August 1, 2015

    Does freezing work? Were the results of the experiment ever published? I used to have a lot of fruit flies around. Now I keep beehive shaped containers with cider vinegar in them, to entice the little buggars, with a little water and just the slightest bit of soap in it–to break surface tension. Any container, like a soda pop bottle with staws poked through as an inlet for fruit flies also works well. I’ve also found in areas where there are many little flies a few minutes with a vacuum cleaner can be very fast and effective.

    • Bentley
    • August 7, 2015

    Yet another post I haven’t kept up with.
    Freezing absolutely works. Pretty sure there is an update in this series confirming this.
    It is rare for me to feed scraps that HAVEN’T been frozen anymore.
    Apart from the fruit fly issue, it also helps start the break down process.

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