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Maggots in my compost bin #877138

Asked July 14, 2024, 9:29 AM EDT

My enclosed compost bin (big green bin with aerator purchased from Costco) is swarming with maggots. Is this a problem? I have read online that it's not . I have not noticed the maggots turning into flies so if the only problem is that the maggots look gross, I can deal with that. The compost is wet right now - fed by a diet heavy on watermelon rinds and the like, with no dry leaves to add until the fall. I have been trying to turn the compost regularly but, to the extent that helps at all, it is temporary.

Montgomery County Maryland

Expert Response

They might be Black Soldier Fly larvae. If you can provide a clear photo with a scale source like a ruler or a coin, that could help us identify. If it is black soldier fly larvae though, it would be fine (desirable, even), but compost should not be wet, or it might turn anaerobic.

If it is foul smelling, beyond rotting food, then it needs some 'browns' or carbon sources. You can add dry grass clippings if you don't use any pesticides on it, ripped up paper bags or news paper works as well.

Refer to our composting page for other tips and let us know if you have further questions.

Emily

Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 15, 2024, 11:45 AM EDT

Hi Emily,

Thank you very much for your response. I have been trying to add dry leaves and newspaper shreds and have reduced the moisture level in the compost bin, but the maggots or whatever they are seem undaunted. Attached are a couple of photographs - please let me know if you can identify whether these are good guys or bad guys.

Thanks!

Patrick

On Mon, Jul 15, 2024 at 11:45 AM Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied August 02, 2024, 10:10 AM EDT

Hi Patrick,

The photos aren't very clear to be able to tell which larvae it is but we are not concerned regardless. Maggots in compost are natural and it looks like they are helping to decompose the carrots. You shouldn't worry about it and it looks like a balanced pile with the leaves added.

Our entomologist is out of the office today but if you are concerned of the species we can check in with them when they return, otherwise we would say don't worry about it and turn your pile when you can to help with the decomposition process.

Emily

Hi Emily, thanks very much. Whatever these are, they have been in my compost bin in huge numbers for many weeks, and have not generated a swarm of flies or anything harmful as far as I can tell. I am curious what they are, but if you're not worried about them, I won't worry about them, either! Sorry the photos aren't very good - inside of a compost bin not conducive to photography...

On Mon, Aug 5, 2024 at 11:57 AM Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied August 05, 2024, 1:47 PM EDT

Hi Patrick,

Our entomologist weighed in:

"We unfortunately cannot identify these maggots to species, but they likely are black soldier fly (BSF) larvae (maggots) as you suggested. BSF larvae encourage a high rate of waste biomass conversion.

Black soldier flies have a larval stage that lasts approximately 14-18 days before they pupate; this can vary based on climate. Also depending on climate, some larvae and/or pupae overwinter and some will die depending on how cold temperatures get. If they remain in the compost pile they could be protected from the killing frosts."

Hopefully this helps!

Happy composting!

Emily

Maggots in my compost bin #877138

Expert Response

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