Fruit Flies: Prevention and Control in a Worm Bin

Methods of prevention of fruit flies in your worm bin


The best strategy for dealing with fruit flies and fungus gnats is prevention. The goal is to reduce chances of infestation. Destroying fruit fly eggs before they enter your bin is key:

  1. The eggs laid on fruit and vegetable peels are on the surface, so scrubbing all produce well before peeling and adding peels to the worm bin is a good start to preventing flies from hatching.
  2. Microwaving waste for 5-10 minutes or freezing food before placing it in the worm bin destroys any eggs that exist in the food waste. Make sure to let microwaved or frozen food return to room temperature before adding it to your bin.

Methods of eradication of an infestation in your worm bin


If you do have a fruit fly infestation in your worm bin, here are some options for how to get rid of them:

  1. Build a fruit fly trap. This is a simple, effective tool for management, especially when used in conjunction with other methods. We recommend having a trap in operation near your worm bin at all times. By trapping the adults, you prevent them from laying eggs in your bin.

    Place some apple or red wine vinegar (NOT white vinegar) in a container with a drop of dish soap to break the surface tension of the vinegar. Then, do one of the following:
    1. Make a funnel out of paper that goes down into the container. Fruit flies are attracted to the vinegar, but once they touch it they cannot get back out and drown.

      Funnel your fruit flies to their demise!
    2. Put a Ziploc bag over the container. Do not seal the bag. The flies can fly underneath the bag to get in, but have trouble getting back out because of the weight of the bag.

      Trap fruit flies with a bag.
    3. Cover the container with saran wrap and secure with a rubber band. Punch small holes in the surface of the saran wrap. Flies go through the small holes and then have trouble escaping and drown in the vinegar.

      Flies enter through holes in the Saran wrap but cannot get back out.

    NOTE: Many people advise using banana peels and other fruit in fruit fly traps. The problem is that flies can continue to fly and breed in these traps. The advantage to the vinegar traps is that flies drown.

  3. Adding a layer of shredded paper or moist coir on the surface of your top feeding tray can help to impede emerging adults and discourage adults from laying their eggs in your bin. This allows air and moisture to escape but thwarts the pesky flies.

    Cover your food scraps with shredded paper to discourage fruit flies.
  4. Another version on this is to add a tray on top of your feeding tray with just shredded paper or cardboard in it. This creates a barrier to fruit flies looking to lay eggs in your food scraps.
  5. One unconventional way to get rid of adult flies and control population explosions is with a vacuum. You can use a rechargeable hand held vacuum near the bin. Also, if you have a powerful vacuum cleaner with a hose, just use it to suck up clouds of flies as they emerge from your bin during feeding, or if they are congregating in another area of the house. The flies tend to cluster around windows and other light sources so that is a good place to look for them. It is possible for fruit flies to live inside the vacuum cleaner so use care when emptying the vacuum.
  6. There are many battery operated fly zappers. The key is to get one that is designed for small insects. This is effective in killing adult flies as they escape from the bin or congregate in lighted areas.
  7. Sticky fly tape can help to control adult populations – situate one close to your worm bin and the flies will get trapped.
  8. Carnivorous plants can put a dent in your fruit fly population when set near the worm bin.

    A Venus Fly Trap plant can help you get rid of fruit flies!
  9. There are also various biocontrol organisms that will help deal with a fruit fly or fungus gnat population. A combination of several biocontrol methods seems to work to eradicate emerging fly populations, however the expense and complication of managing this method often renders it impractical.
    1. A bacteria called Bacillus thuringiensis can be applied as a soil or compost drench to help kill off larvae.
    2. Another method is a predatory mite called Hypoaspis miles that eats gnat and fly larvae.
    3. Predatory nematodes called Steinernema sp. also kill larvae.
    4. Neem is an organic oil found in many garden centers that can be sprayed to control pests in and around the garden. This should be used only when you have an extreme infestation because it has some negative effect on the beneficial organisms in the bin, but it does not harm the worms.

5 Responses to Fruit Flies: Prevention and Control in a Worm Bin

  1. Jacqueline says:

    I made the vinegar fruit fly traps as described in A and B above. I did not start trapping them until I removed the funnel and the plastic bag. So I now just have open jars of vinegar and that is working. Also got out my little vacuum and trapped several in there.

  2. Lucas says:

    The vinegar trap works well. We just leave it open to the air and within a day or two, there are lots of dead flies sitting on the top.

  3. Kurt says:

    Anyone know if Food Grade Diatomaceous Earth would be harmful to the worms? I believe it would help keep pests away. Not sure how much it would dry things out.

    • kate says:

      Kurt, food grade Diatomaceous Earth is not harmful to worms when used in small amounts. If you perform a search online for “diatomaceous earth in worm bins” you will see some tips on how much to use.

  4. Jeavonna Chapman says:

    Thanks. Fruti flies showed up in force this year.

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