Maggots in Compost? Here’s What You Need to Know

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When I opened my compost tumbler a few days ago, I got a nasty surprise.

Maggots! Gross! Disgusting!

Or are they?

Maggots in compost can be a disgusting sight to behold, but are they bad for your compost? I recently got a question from Steve R., an Epic Gardening reader:

“I have been using a compost tumbler for the first time and am seeing a lot of big maggots. I think I am composting correctly (no fats, meats, etc.) but they are still there. Are maggots bad for my compost? Or what’s up?”

Let’s answer this question once and for all.

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The Culprit: Black Soldier Fly Larvae

Maggots in compost?

While there are a few other types of maggots that might show up in your compost, the most common culprit is the larvae of the common Black Soldier Fly, or hermetia illucens.

You’ll be able to identify them easily due to their fat appearance, usually in a whitish, greyish, or brownish color. The color can change depending on what they’re eating.

Black soldier flies might be annoying when they’re buzzing around your face, but these flies are actually incredibly useful. In fact, there are farms that cultivate the larvae and sell them to pet stores, as they’re a great food for birds, lizards, and even fish!

But what does this have to do with them being in your compost? Are they a good thing or a bad thing?

Let’s look at why they show up in the first place.

Causes of Maggots in Compost


If you’ve ever gone crazy trying to swat flies in your kitchen, then you already know exactly what causes these maggots to show up in your compost: food waste. Black soldier fly (BSF for short) larvae absolutely devour food waste, so long as they have a warm, moist environment to chow down in.

If you have too many ‘greens’ in your compost and not enough ‘browns’, you shouldn’t be surprised to see a bunch of these guys in your compost.

Another potential cause is not mixing or turning your compost pile, leading to moist pockets of food waste that maggots will flock to.

Solutions for Maggots in Your Compost

While you don’t HAVE to do anything if the maggots you’re dealing with are black soldier fly larvae, you may want to for one of two reasons:

  1. You find them gross and don’t want them in your compost, no matter what
  2. There are simply too many and it’s interfering with the progress of your compost

Solution 1: Add more browns

These maggots do well when they have a lot of food material to feed on and a relatively moist environment. To combat that, simply add more brown materials to your compost to dry it out a bit and lower the percentage of food matter that larvae can find and feed on.

Solution 2: Lime your compost


Usually you don’t have to add lime to your compost — it breaks down just fine. The danger of adding lime is that the pH of your compost may be too high by the time it’s done. But if you want to combat maggots, you can:

  • add about 1 cup of lime per 25 cu ft. of compost, or
  • add pine needles to your compost, or
  • add citrus fruit waste

Any of these will work to combat the proliferation of maggots in your compost.

Solution 3: Make sure you aren’t allowing flies in to your compost bin / tumbler

The only way you can get maggots in your compost is if an adult BSF lays eggs. So while compost needs good airflow, that doesn’t mean that you need to provide huge holes for the flies to enter and exit from. Covering the air holes with a mesh screen is often enough to stop more eggs from being laid.

Solution 4: Let them be!

Like I said, you don’t have to get rid of these maggots. In fact, some gardeners love having them in their compost because they break down food waste so quickly. As long as you give them a warm and comfortable environment, you’ll probably never see faster compost than when black soldier fly larvae are processing it for you.

If you have chickens or pets, they also may like to hunt for the BSF larvae once you’re compost is finished. They can be a great food source for the other animals on your property if you keep them around!

However, the compost that comes out may not be the most appealing. It usually doesn’t have that rich, earthy smell and seems a bit ‘off’. It’s understandable that they may not be the most appealing things to have in your compost, and they also get less effective as the weather cools down, so you can definitely remove them and use the classic composting method as well.


The Green Thumbs Behind This Article:


Kevin Espiritu
Founder

Maggots in compost can be a disgusting thing to see...but are they bad or good for your compost? Find out the answer, along with what causes them!
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43 thoughts on “Maggots in Compost? Here’s What You Need to Know”

  1. I have tried red wigglers in my compost tumbler for several years. Although they last for awhile, it is never for very long. Soon the BSF larva take over. The BSF don’t seem to harm the wigglers directly but they eat the garbage a lot faster than the wigglers plus they reproduce faster. I can’t keep up with making enough garbage to satisfy both of them! I think the wigglers end up starving.

    • My guess is that the wigglers actually get overheated and die off. Compost tumblers are bad environments for red wigglers to be in, as they’re designed to heat up and help decompose waste quickly. Comparatively the black soldier fly larvae are used to warmer environments, so that’s probably what did your wigglers in.

  2. Ok, so when is the best time to stop adding green-food waste to a maggot-ridden compost pile so that the maggots will die off and the pile can begin to age?

    • Whenever you’d like, honestly! Composting happens year-round. However, it’s much faster to compost and to age your pile when the weather is warm, and we’re heading into the fall months.

      If your area gets cold over the winter, you may want to go ahead and keep adding green and brown waste to your pile for now (use about twice the amount of brown waste to each batch of green waste). You can then stop once the weather begins to warm up again and turn/mix/moisten it to kickstart the composting process in spring.

      The warmer the conditions both weather-wise and inside your pile, the more rapidly your compost will break down. You can add a compost starter to your pile to try to encourage the pile to naturally warm up on its own, but if you don’t have a good balance of brown waste to your green waste (which is usually the biggest cause of maggots), you won’t be able to maintain heat inside of the pile.

  3. I have recently discovered these in my bin also, what happens in the spring when I want to spread the compost in my garden…. do I have to remove them??
    Thanks,
    Melanie

    • Before you use compost in the garden, it should be well-aged with no fresh material in it anyhow. By that point, any maggots will either have died off or will have matured into adults and flown away.

      I usually use either a double-sided compost tumbler or two separate compost piles or bins. One of them will be my “active” compost, and that’s the one I’ll be adding fresh brown and green materials to. The other will be the “aging” compost, which is when the material is going through its decomposition process and no new material is being added.

      During the aging process, the maggots generally disappear on their own, as there’s eventually nothing left for them to eat that hasn’t already broken down. This is also when the compost begins to take on the rich soil-like smell associated with a great compost. When it smells like great garden soil, it’s time to use it!

  4. The maggots in the compost bin become so big and fat
    Eventually they will turn to huge flies and fly away once I open the lid. Right?

    • If your maggots turn to flies, they’re old enough to start the next generation if they don’t get out of the bin quickly. They’ll lay more eggs, and you’ll have more maggots!

      The best way to eliminate maggots from your compost is to regularly turn it and to add more brown waste. You can also put sheets of dampened newspaper over the top of the compost, which will prevent some flies from getting in there to lay more eggs. Another option if you don’t have newspaper at hand is a thick layer of dry leaves or straw overtop if you’re not going to turn it for a while.

      Regular turning and aeration of the interior of the compost bin tends to allow the compost to break down more quickly. Usually, flies don’t come around if there’s not a lot of green waste, so adding more brown waste (dry leaves, paper, shredded cardboard, wood chips or pellets) may also deter maggots from forming.

      • I have a 60 gallon in ground compost digester. I add ALL food waste to it for a full year, including meat, dairy, etc.

        Every fall I shovel out the bin and get the garden rototilled.

        When the weather warms up after winter it does attract flies and with them come maggots.

        I find that the maggots really help break down the food waste. They help control the smell of rotting food. And they also reduce the level enough that a full years worth of kitchen waste can fit in the bin.

        • In ground digesters are much different than the average compost pile or tumbler in how they work — they’re a cold-compost system instead of a hot compost system. They do develop maggots, and it’s true that the maggots will break down the waste significantly. In fact, what you’re doing is not too different from black soldier fly composting, in a way!

          But for a lot of people, especially those in urban areas, maggots can become an issue. Imagine having flies buzzing around your apartment balcony because your tumbler’s full of maggots – it’d be unpleasant to be out there. Or worse, your neighbors might start to complain about the flies that’re drawn to your compost. In cases like that, it’s best to stop the maggot infestation, even though they do a fantastic job of breaking down the waste.

          In-ground digesters are fantastic, though, especially if you have enough property that the flies don’t become a nuisance. Sounds like you’ve got a great system that works well for you!

  5. The sides of my compost pail are absolutely swarming with maggots when I open the lid, as if they are trying to escape, like something out of a horror movie! And it smells putrid. Should I try to scoop out as many as I can? But do what with them?! I’m getting scared of my compost bin!

    • This is usually a sign that while you’re great with adding food waste to the compost bin, you’re not as good at adding “brown” waste. Add shredded paper (newspaper is great) or shredded cardboard, fine wood chips, dry leaves, or even horse stall wood pellets to your bin.

      Brown wastes absorb liquid in the compost, which stops a lot of that putrid, rotting smell. And as that smell is what’s drawing the flies, you want to stop that smell at all costs to prevent the maggots from appearing.

      It might be good to add some compost starter to your bin and to turn the contents more regularly as well. This allows heat to build up in your compost, which will kill off maggots inside of it.

  6. Hello there,
    I just opened my compost bin to find soooo many of the gigantic maggots. I was so freaked out. Thanks to this article I found out what they are. My composte is mostly kitchen waste mixedbwith soil. Food leftovers. Should I add more dry stuff?It’s getting really smelly. When do we start to use the compost? How do know when it is ready and what texture and smell should it be?

    • Here’s a few tips for you!

      If your compost smells like it’s rotting, you definitely need more “brown” materials. Shredded paper/newspaper, shredded cardboard, dry leaves, fine wood chips, or wood pellets of the type used in horse stalls is what I usually add to mine. These brown materials will absorb the moisture created by the greens breaking down.

      Turn your compost regularly. If it’s in a stationary bin, you can use a shovel or a compost fork to do this. If it’s in a compost tumbler, just spin the tumbler a few times. Do this at least once a week. It allows air to penetrate the pile and helps cause heat to build up in its center, which will kill bugs and sterilize the compost.

      When you add a layer of green materials (like food waste), add a layer of brown materials overtop of it. Even if it’s just handfuls of shredded newspaper, it can help prevent flies from laying eggs in the food scraps as they break down. A piece of tarp over the pile can also stop flies.

      If you are constantly adding waste to your bin, that bin will never really be “ready” as there’s always going to be fresh materials in it that haven’t broken down. For best composting, you need either two bins (one to age and one to add to), or a double-sided compost tumbler.

      You will be able to tell when your compost is ready for use when it looks like a storebought compost (maybe with a few larger chunks still left) and it smells like good garden soil. That process can be fast if the pile is kept hot, or very slow if it’s cold-composting or in the winter months.

      Before using it, sift out larger chunks by passing it through a hardware cloth screen, and add those larger chunks back to the pile for more aging.

  7. Hi Kevin, thanks for the article. Very helpful! My composter is full of BSF right now and I’ll keep filling the bin until it’s almost full. My question is: when the compost is done, will the BSF still be there? That would not be fun getting the compost out and using it…. Thank you!

    • Yeah I like to control their population a bit and not let them get TOO crazy. Eventually they will eat all the food and won’t be able to feed, so I’d imagine the laid eggs would hatch and then the larvae wouldn’t survive. You could let the compost fully finish so there wasn’t much left for them to munch on, then retrieve it!

  8. Iโ€™m not sure if the maggots in my compost digester are BSF or not but they sure help reduce the volume of the bin.

    I throw ALL kitchen waste in the bin and only empty it once a year in the fall after the garden is harvested.

    I find that when the maggots arrive the stink is drastically reduced and the level drops enough that there is room for a full year of waste in the bin.

    I add kitchen waste all winter and summer. In the fall I shovel it out and rototill the garden.

  9. Hello!
    I know this maggots are “friendly” in my compost bin, but they recently started fleeing the compost bin, making the neighbors understandably upset. I swiped them away with a water hose, but today there are more! How can I get them to stay in the compost bin? Why are they fleeing? Do you think it’s because of warmer temperatures? Thanks!

    • Could be because of conditions inside the bin – too warm, not enough food, they’re actually becoming flies…etc. I’d try to adjust your bin so they’re a bit less prone to stay there ๐Ÿ™‚

  10. Hi Kevin, I have a lot of these maggots in my compost, I just put in a whole lot of tiger worms as well, do you think the tiger maggots will affect the worms?

  11. My last compost bin had an explosion of the Black Soldier Fly larvae and yes it did break down super fast. I emptied the bin out for my chooks to pick through but after a while they too had had enough. I ended up burying it under soil in an empty garden bed. What will happen to the remaining larvae? Will they keep developing and turn into a zillion flies? Thanks

  12. Hi Kevin, our family owns and operates one skilled nursing facility in Massachusetts. We have some Clivus composting nepotism flush toilets that have been in testing here since 2005. Our new addition will only use these composting toilets. My question now is regarding composting of adult diapers. Our family would love to join or become a test participant for this. I have done some research on this issue, and cannot find much on it. We use a great deal of disposable adult diapers that have a plastic lining. Would maggots combined with other organisms have any chance of breaking down the entire diaper?

    • Hi Carol, I’m sorry I can’t be of more help, but I don’t know much about adult diapers. If it’s plastic lining, as far as I know only a select few species of bacteria are capable of breaking plastic down and I’m not sure they’d be present in a composting toilet environment. Sorry!

  13. Hi. Very helpful article. I too am puzzled by the comment about adding citrus waste, as the maggots in my compost bin are only in the half-lemon rind ‘cups’ discarded after juicing them. Nowhere else.

  14. I’m pretty sure that “my” maggots are fruit fly maggots from my kitchen waste. They were all over my food waste, especially banana skins. When I took the stuff out to the compost barrel – the rolling type – I think they laid their eggs there.

    • Oh no! Annoying. While they will probably break down your waste faster, it’s probably not a good idea to have a breeding ground for those little guys so close to the home!

  15. Thanks a lot, very enlightening. I have two bins side by side. Both were re-populated with red wigglers about 3 months ago by me. In one bin there are only the worms; in the other there are so many maggots that I literally can’t see worms. I will try “more brown.” I do have to ask why lime or citrus waste both work when they should have opposite effects on the pH? Aren’t pine needles also very acid?

    • You’re welcome Stephen. I think it’s definitely a balance – maggots are OK, but too many will cause compost to be a bit “icky” when finished. Lime / citrus waste would both be acidic, unless you mean calcium oxide when you say “lime”

  16. Black fly larvae don’t usually bother humans so much, they are attracted to decaying food, so as long as you don’t have any decaying food right next to your house you will likely never see one. They are fantastic at processing your compost and are being used in trials by several universities for food waste utilization. I would be very happy to have black soldier fly larvae in my compost bin, but i agree, they don’t look so pretty. Just shut your eyes!

    • Yeah, they don’t look great. The definition of GROSS. I’ve heard some readers say they process compost TOO fast and don’t leave it in the best condition, but in my opinion I’ll take some speedier compost processing ๐Ÿ™‚

  17. but if we leave them, aren’t we fostering a fly nursery? I don’t want to be breeding flies near my backyard. please advise!

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