Fruit Flies Invading Your Worm Bin? We Can Help

Fruit Flies Invading Your Worm Bin? We Can Help

Why Do Fruit Flies Like My Worm Bin So Much?

Your worm bin is a smorgasbord of delicious, decomposing food scraps—if you have healthy looking, hardy worms, that’s an indication that your worms are absorbing rich nutrients you’ve been providing from composting material. Those rich nutrients are just as delectable for other insects, as well, and those other insects can be a nuisance.

Fruit flies love worm bins for this reason. They have access to a large source of ample food where they can find nourishment and safe areas to lay eggs.

You probably found this page because you’re having issues with fruit flies in your worm bin. We will help you figure out why the flies are there and how to get rid of the fly infestation for good.

Getting Rid of Your Fruit Fly Infestation

Getting rid of your fruit fly infestation shouldn’t be too difficult. We have a variety of strategies to use in your fight against them below.

  • Eliminate large clumps of rotting food. When you feed large pieces of food to your worms, the worms generally can’t consume them before nature takes hold and the food starts the process of decomposition. When this food breaks down, it creates chemicals that fruit flies are attracted to. By getting rid of these large chunks, you are removing most of the suitable egg-laying space, which should put a huge dent in the fruit fly population.
  • Add a thin layer of moist coir or newspaper on top of your feeding area. This will work to keep flies from getting in and laying more eggs, and it will also work to keep existing adults from getting out. Like a surgical mask, air and moisture will still be able to flow between the world and your worms, but the pests will be blocked from entering and exiting. Another way to use this “barrier method” to your advantage is to add cardboard or shredded paper as an additional tray above your food tray.
  • Make your own fly trap. This can be as simple as setting a little jar containing a mixture of red wine vinegar and dish soap on your counter. Within a day or two, you will start to notice a collection of dead little flies floating on top. If you’d like to try other trap methods, consider making a paper funnel that will invite fruit flies down into the vinegar but make it nearly impossible to fly back out.
  • Buy a battery operated electric fly trap designed for small flies.
  • Buy fly tape and string it above your garbage, your worm bin, and any other problem areas. This sticky adhesive tape can be found at stores such as Walgreens, Kmart, Wal Mart, Target, and Lowes.
  • Place fly-repelling plants near your worm bin—especially carnivorous plants such as Venus Fly Traps. Carnivorous plants are a chemical free, symbiotic way to get rid of flies—eliminate your infestation while simultaneously supplying food to a plant!
  • Neem Oil does not harm your worms and can be sprayed to control flies. Although it is an organic oil and has no negative effects on your worms, it does have negative effects on the beneficial organisms in your worm bin. Consider using in cases of persistent infestations.
  • As a last resort, if nothing is getting rid of your fly infestation, consider biocontrol methods such as Bacillus thuringiensis, a bacteria that kills fly larvae. There are also predatory mites and nematodes that eat fly and gnat larvae, such as Steinernemas and Hypoaspis mites.

Preventing Flies in Your Worm Bin in the Future

The key to preventing future fruit fly infestations is to eliminate the odds of stray fly eggs or larvae ending up inside your worm bin.

One of the best ways to do this is by throwing your food scraps in the freezer. Flies lay eggs on the surface of your scraps without you realizing, and freezing compostable food scraps will destroy all fruit fly eggs have already been laid on the food. These eggs would otherwise thrive in your worm bin and potentially begin an infestation.

If you choose to freeze your scraps before you compost them, be sure to let the compostable materials thaw out first before you add them to your worm’s home. Remember, red wriggler worms are drastically affected by temperature change. Adding frozen food scraps to your worm bin could cause their living environment to become too cold for comfort, harming your worms’ ability to eat and reproduce they way nature intended.

You can also microwave compostable materials for at least 60 seconds. Again, make sure the food scraps have settled back to room temperature before adding them to your worm bin. You don’t want to burn your worms! The extreme temperatures could mean death for some of your worm buddies. The worms will squirm away from the heat to cooler, lower layers of their trays. This will also cause them to eat and reproduce less.

If the above two options seem too laborious for you, at least try washing food scraps before throwing them in the worm bin as anything helps when trying to prevent a fruit fly invasion.

A Few Extra Tips on the Fly

Female fruit flies lay hundreds of eggs during their short (~50 day) lifespan. As we learned above, the fragrance released by rotting food attracts the flies and alerts them to a prime breeding spot. Moist, spoiled fruits and vegetables (exactly what you’ll find in a typical worm bin) make it difficult to combat invasions, but there are other useful preventative measures you can take to keep your fly friends away:

  • Make sure your worms are eating food scraps at a rate that prevents food scrap pile-up. If scraps seem to be piling up, adjust your feeding rate accordingly.
  • Consider placing a fan close to your worm bin to create an air current that will prevent fruit flies from approaching your worm bin. Keep in mind the temperature and moisture of your worm bin—if you notice the worms knotting up in a ball, the fan is messing up the conditions in your worm bin, making them cold or dry. The fan will also carry the ripe smell away from the worm bin, making it hard for flies to find any faint fragrances they might use to make their way to composting food.
  • Keep your kitchen sinks and eating areas free of food scraps.
  • Consider pouring bleach (or whatever cleaning agent you prefer that is appropriate for kitchen use) down your sink drains. When we wash our plates and utensils, we don’t think about the tiny food scraps that collect in kitchen drains. You might even want to run your garbage disposal while pouring in the cleaning agent to ensure it makes contact the entire inner surface of your unit, eradicating any flies/larvae that may be present. Moist areas with tiny food scraps are the perfect area for fruit flies to breed and hide, so adding a cleaning agent to your drains is important to fully eradicate a fruit fly infestation from your home.

No matter what technique you utilize to end the fruit fly infestation in your worm bin, the most important thing to remember is you NEED to proactively engage in prevention, or the fruit flies WILL come back.

Using all of the techniques on this page, you will surely get rid of your infestation for good. Now get up and go apply this new knowledge to your fruit fly problem! Best of luck and happy worm composting!

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Article by Natalya Cowilich

Readers Comments (20)

  1. A hand held vacuum cleaner will suck up a lot of fruit flies. My grandson loves chasing them with the vacuum!

    • Ah yes, I’ve had fruitfly battles with my vacuum hose extension. Lotsa fun! To tell you the truth, there was a time when I expected fruitflies to assault me every time I opened the bin- so I started taking them into our tiny powder room to contain the “battle” at feeding times.

  2. Why not milling the defrozen/microwaved food before serving it to the worms by pouring it deep in the bin?

    • Using a blender to process defrosted or microwaved food is an excellent means of added protection against a new fruitfly invasion. However, it is the freezing and microwaving that will actually destroy the eggs or larvae before they are blended. Even so, blending is a great way to make meals easier for your worms anyhow.

  3. Samantha Dawson July 28, 2018 @ 11:47 am

    In the summer months we have a problem with small ants taking over our worm bin. We have a very healthy worm bin except for this. What can be done?
    P.S we live in Australia if this makes a difference

    • Hi, Samantha. I’ve heard of ants being pests in the worm bin before! I believe it may almost be a common problem because the manufacturer of The Worm Factory line of products has designed the legs of their worm bins to stop ants from being able to make their way up and into the trays. If you have something similar with legs, setting each leg into a bowl or cup of water should undermine any newcomers. Another water suggestion would be to run water through your worm farm once a week- enough that all the bedding is quite damp. Catch the excess (leachate) for fertilizing purposes. Ants aren’t fond of very moist conditions. They are drawn to sweet foods, like fruit peels. Avoid these to aid in the process of deterring ants. Others try dichotomous earth beneath and surrounding their bins to detract and kill ants. Best of luck! We’d love to hear which route you take and how it goes!

    • Ants don’t like moisture…..

    • Hello. On each leg of the worm farm place the foot of the leg in a small bucket of water to create a moat that the ants won’t be able to swim across to travel then up the leg into the worm farm!

  4. Bharatdas Devmurari October 16, 2018 @ 9:18 am

    I have a worm bin first time and the new worms are growing very healthy, but I have noticed the ants has invaded into worm bin. I have tried to keep the worm farm moist all the time but the ants are still there. I am wondering that the ants may start eating worms? If yes, then can any worm lover suggest an idea/ideas to avoid ants entering in worm bin? I live in NSW Australia and some areas in my region has ant infested soils.

    • Hello Bharatdas! Great to hear from our worm composting friends in Australia! I hear the ants are a real issue there. If you are able to set your worm bin up on legs that can be set into bowls of water, that can possibly prevent them from being able to get up to the bin.
      To get the ants OUT, you may have to add significantly more water. The worms can handle 85% moisture pretty easily for a bit- and that might help you get the ants to leave so that you can start fresh. I’m not sure if your ants are worm eaters. I’ll hope not!

  5. I’ve just gotten an exploding population of the dark-eyed fruit fly. Its slightly bigger than the red eyed flies, and isn’t attracted to vinegar at all, and seems to be breeding quite well even though all food is buried very well. Any suggestion on how to deal with this?

    • Hi, Ryan. Sorry to hear about the fruit fly boom! I find that type to be slightly slower- if that makes you feel any better- they are easier to suck up with a vacuum that way! I’d suggest baiting them with a nice sweet piece of fruit on the counter- once they congregate- suck them up and then maybe leave your vacuum in the cold (if you have it) to make sure they expire.

      As for your worm bin- put a hold on the feedings other than maybe moist cardboard for a week or so if the worms can handle that. Let sweet foods be eaten up so that there are no more temptations for fruit flies to be drawn to. Also, if it’s cold- maybe drag your bin outside to open it up for one sec- the fruit flies will fly up, freeze, and fall to the ground.

      Best of luck! Let us know if you come up with something else creative and useful!

  6. Other than the fact that fruit flies are a pest inside the house, are they detrimental to bin health at all?

    • Hey Quinn. The fruit flies themselves are of no detriment to your worm population. However, sometimes a fruit fly outbreak tells of unhealthy conditions already existing in the bin. Just make sure you are keeping on top of moisture and pH levels. Using a simple probe meter will help if you want to be sure.

  7. I think my worm bin might have mites…they look like tiny red spiders. What do I do?? Please help!!

    • Hi Suzie, mites generally indicate excessively moist conditions. They like it where it’s moist, so to get rid of them you can try to dry things up. One way I like to take a two-fold approach is to lay some
      dry bread and newspaper flat over the top of your moist bedding. Press it gently down so that it’s making contact. with it. The newspaper will absorb the excess moisture and the mites will come for the bread which will also soak up the moisture. Once the mites have gathered and the bread and paper have soaked up excess moisture, you can take them right out of your worm bin. Hope that helps you get them under control right away!

  8. Vickie Darling May 1, 2020 @ 9:24 pm

    Can you feed worms ground up crab legs and mussels

  9. A venus flytrap cannot contral fruit flies, which are much too small. Some diffenert carnivorous plants may work ok.

  10. Got fruit flies infection. Probably from unfrozen banana peels. Now they’re flying around and sticking to yellow stickers like mad.

    Thanks for the biocontrol idea. 10million Steinernema feltiae ordered.


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