Flying pests

Early Spring means it’s time to get outside and enjoy the garden! However, this also means that many bugs start to awaken too. Sometimes these pests can even get inside the house! Worse yet, sometimes these annoying pests can make their way into worm bins. This post will explore the common flying pests and how to prevent or get rid of them.

There are a number of flying pests that may inhabit a worm bin. After all, most worm bins have the perfect conditions that these pests are attracted to: damp, dark, decomposing matter.

Outdoor vs. Indoor Vermicomposting

I have mentioned in some prior posts that indoor vermicomposting is far easier to maintain because you don’t have to fight mother nature. Dealing with flying pests is no different. Outdoor systems will inevitably have some sort of flying pest and will never be 100% pest free…at least not without a LOT of effort and constant monitoring.

Indoor systems tend to be much easier to maintain against flying insects since there are a number of barriers against them. Flying pests are typically introduced to indoor systems either by fruit peels where they lay their eggs or the type of bedding. Leaves, straw, woodchips, or any type of bedding that was outdoors can harbor flying pests.

Common flying pests in vermicomposting systems

The following are the most common flying pests:

  • Fungus gnats
  • Fruit Flies
  • Black Soldier Flies
  • Mosquitoes
  • Scuttle Flies


As with many things in life, prevention is the easiest and best way to keep flying pests out of vermicomposting systems. Here are a few strategies to keep the pests away:

  • Keep a dry layer of bedding on the top surface. Flying pests will lay their eggs on damp surfaces so they will avoid the top layer.
  • Bury food scraps. This is especially important for outdoor systems. This will even help prevent other types of pests (mice) if the scraps are buried under a thick layer of bedding.
  • Use a fully enclosed system. Systems like the Urban Worm Bag or the Vermibag are breathable but fully enclosed systems. This acts as a barrier against the pests. Plastic totes with drill holes can incorporate window screen to keep the pests out.
  • Freeze the food scraps. Fruit flies lay eggs in the skin or peels of many fruits. Freezing the scraps will kill the eggs and larvae. The additional benefit is that the scraps will decompose quicker which gives flying insects less time to find the scraps.
  • Cardboard and paper bedding material. These materials are generally free of pests when kept inside. Using decomposing leaves, straw, compost, or woodchips may contain these pests. This is why I recommend only using cardboard or newsprint for indoor systems. However, I will note that the microbiology of leaves and other outdoor type materials is far superior.
  • Mosquito Dunks or Bits. If you have to use a bedding material like leaves, it’s best to add some Mosquito Dunks or Bits into the material. Mosquito Dunks are a natural bacteria that kills gnat larvae and mosquito larvae.

The prevention strategies work very well for indoor systems. The take away for indoor systems is to limit the amount of outside material and freeze scraps. This will prevent the majority of flying insects from getting into the systems. These measures won’t ensure 100% success against flying insects but will greatly increase the odds against them.

These strategies will also work with outdoor systems too but won’t be as effective. A very generous layer of dry bedding is the best bet for outdoor systems. Mosquito dunks are also a good idea to prevent gnats and mosquitoes.


Even with preventative measures sometimes these pests still find a way in the system. Some pests are far easier to deal with than others and more often that not multiple steps will need to be taken.

Gnats, Fruit Flies, and Mosquitoes


The easier pests to deal with are fungus gnats and mosquitoes. The addition of Mosquito Dunks to a bin will kill off the larvae of these pests. This will eliminate future generations of these pests. To deal with the adults, add some dry bedding and don’t feed the system for a few weeks. This will starve the adults and eventually eliminate them. Mosquitoes need blood to reproduce but do feed on sugars.

Fruit flies are unfortunately very persistent and difficult to eliminate. There are two common ways to eliminate them. The first method is a vinegar trap. Use a small bottle with some vinegar (apple cider or red wine types work best) with a funnel in the bottle (can be made of paper). The flies are attracted to the vinegar and will fly into the trap. Once in the trap they have a difficult time flying out. They will end up drowning. Once a day the vinegar should be replaced. Keep up with this until the flies are gone. The second method is using a vacuum. Using the wand attachment, slowly open the bin and suck out the flying flies with the vacuum. Constant attacks with both methods will eventually get rid of them but this takes time and patience. Also, stop feeding the worms. They will survive off of the bedding material. The Urban Worm Company has a post with some more detail on how to get rid of them.

Another method that can be used against fruit flies is Diatomaceous Earth (DE). I wrote a recent post on the basics of DE. This can be used in conjunction with the vinegar traps and vacuum. Add a layer of dry bedding to the top surface of the vermicomposting area. Then add DE to the entire dry surface. DE can dry out the flies bodies and ultimately kill them. Just remember to wear a mask and eye protection when working with DE. Also, DE needs to be dry to be effective.

With both the gnats and fruit flies it is best to stop feeding the worms any scraps and allow the system to dry out some. This may not be ideal for the worms but they are VERY resilient and can survive this temporary disruption.

Black Soldier Flies

Black Soldier Fly Larvae

Hmmmm. This is tough. Just for some background, Black Soldier Fly larvae (BSFL) are one of the best decomposers. They are much faster at processing food scraps than worms and will eat just about anything. In fact in an outdoor system these larvae are beneficial. Indoors however, they are a nuisance. Now the flies themselves are quite harmless and don’t bite. They are rather large but don’t fly very fast and are relatively easy to catch. Catching the adult flies is not that difficult and easy to remove. However, the larvae are more difficult.

Prevention works best with BSFL. The main method is to not use outdoor bedding materials like leaf mold. Once the BSFL are in a system the only way to get rid of them is to pick them out. Obviously this isn’t easy as they can be anywhere in the system. In general, I have found that they tend to go in cycles and are only an issue during the summer months. If I do find BSFL in my systems, I simply bring them outside to my outdoor compost.

I don’t really find BSFL to be pests but I prefer to not have flying insects in my house.

Scuttle Flies

Scuttle flies resemble fruit flies but they have an odd behavior. Instead of flying like fruit flies, they often “run around” to avoid predators. Scuttle flies are also not as picky about the foods they go after and can quickly get out of hand in an indoor environment. Prevention is the best course against these!

Trapping them seems to be the best way to eradicate them. Here is a post from RedWormComposting that explains the traps and how to use them.

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