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

Black soldier fly larvae in compost?


When I opened my compost tumbler a few days ago, I got a nasty surprise. There was an abundance of maggots in compost to be found! 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. Are maggots in compost bad… or are they good?

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The Likely 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

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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 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 many 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, add more brown materials to your compost to dry it out 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 into 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.

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