Mystery of the Disappearing Worms

Here is a recent e-mail I received from Gordon C.

Dear RWC/Bentley – I just suffered what appears to be a massive worm disappearance, the earthworm equivalent of colony collapse disorder, and I’m wondering if you can give me any ideas on this –

In short, I’ve been tending worms for close to a year and things have generally gone well up until a black soldier fly infestation about a week and half ago. After figuring out that the rotting veggies in the worm bin were the likely source, I put a thin layer of coir on top of the bin, which was at the time fairly chock full of worms. (And put up fly strips for the flies.) I noticed the next day that some of the worms were crawling up the sides of the bin, which is not completely unusual, and I also found a few outside on the floor – definitely more unusual, but not unprecedented and not fatal. A few days later (I had to go out of town just as this was happening), I chopped up some fresh veggie scraps and froze them, which I’ve been told is a good way to kill any fly or other larvae and eggs that may be in them. I then let them sit outside for two days in a sealed plastic bag, in a shady spot. Then, yesterday, I put the fresh scraps in along with shredded newspaper for bedding. A few more were crawling up the sides, and another handful were on the ground outside, and I saw a few worms inside but didn’t thoroughly inspect. Today I did inspect thoroughly, and could only find a tiny handful of worms – like maybe 10. So many hundreds of worms seem to have vanished in the space of a week or so.

Thanks so much for any guidance you can give me on this – it is confusing and concerning me as well as bumming me out!


Hi Gordon,

There are a number of potential red flags in the information you shared with me:

– Black Soldier Fly Larvae
– Leaving town
– Food waste sitting outside, sealed in a plastic bag

Let’s look at each one in more detail…

1) Black Soldier Fly Larvae – while these guys CAN basically co-exist with worm in a vermicomposting system (they don’t attack the worms or anything like that), their presence may indicate that conditions have shifted away from “ideal” for the worms. They tend to appear when temps are pretty warm/hot, and their fast waste-processing can result in even more heat being produced. A good strategy when you start to see these guys is to slow down your feeding a lot and add loads of bedding instead. The larvae definitely prefer a waste-rich environment, so you’ll likely start to see a decline in their numbers after a while.

2) Leaving town – I can’t tell you how many times I’ve heard about worms disappearing when people have gone away for a period of time. The problem is that any number of different things can go wrong during your absence – especially with an outdoor system, and extra-especially (lol) when people add more food than normal so as to compensate for a lack of feeding while they are away. My hunch is that your system IS outdoors (perhaps in a garage or shed?) – since there are BSFLs in it – but I don’t think you are guilty of adding too much food before you went away (it sounded as though you fed them once you got back). But it does seem as though the situation only got worse in your absence.

3) Food waste, sealed in a plastic bag outside – when you are aging food wastes it is definitely a good idea to try to keep them as aerobic as possible. If they get sealed up and are allowed to turn into anaerobic goo they can end up with various compounds that may be harmful to the worms (alcohols etc). I’m glad you at least mixed it with bedding when you added it. Hard to say for sure how much (or even IF) this contributed to the worm decline, but I definitely wouldn’t be surprised if it did.

I think overall this was a combination of factors – likely excess heat combined with declining habitat quality due to the BSFLs and (maybe) the wastes you added.

My suggestion would be to mix in lots of lightly moistened bedding, and stop feeding altogether. If you haven’t been monitoring temps, make sure to start doing so.
Feel free to share a few more details about your set-up and surrounding environment as well. Where exactly is it located? What type of bin is it? What are ambient temps like?

Hope this helps a bit!

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    • Chris
    • July 9, 2013

    Regarding 3, what I’ve been doing with my frozen food waste, is putting some ripped up dry cardboard in the bottom of a bucket, then the food waste on top of that, and I cover the bucket with a bit of old speaker cloth (though any cloth that can breath would work, it just allows air in while keeping flies and such out), which is secured to the bucket with a rubber band. Then I just leave that out for a few days, mixing it around a couple of times.

    I actually do pretty much the same thing with my plastic stacking tray system, using a cloth cover secured with elastic rather than the plastic lid.

    • Bentley
    • July 10, 2013

    Sounds great, Chris – thanks for sharing that!


    • Janice
    • July 12, 2013

    Help I just ordered worms for my compost and I live in…….Phoenix AZ any words of wisdom will be Greatly appreciated Thanks

    • Gordon
    • July 16, 2013

    Thanks for the answers, Bentley, some good points there. To add the addition information you suggested, my worm bins are inside, in a utility room of a basement which has one small window but no direct light, because the window looks out on a covered basement entrance. Temps during the summer get to the low 70s in the room. I am thinking that the excessive moisture at the beginning of this whole process probably started the whole thing in motion, however the BSFL got in there. (I am incredulous that I never saw them in the bin.) While I have produced at least one batch of perfect consistency finished vermicompost using shredded newspaper as bedding, it does seem hard to keep the moisture level right, because when I add a lot of bedding it takes a very long time to break down. (My first batch was more like vermicpompost coated paper as opposed to just compost.) Do I simply let it get to that point and then stop feeding them, just let the newspaper shreds take however long they need to break down?

    I will look for more info on your great site on this, feel free to point me to a link if you want.

    Oh, and one other question – am I correct in believing that freezing is a good way to kill any larvae that might in the food I give the worms – so long as I defrost it under aerobic conditions before giving to the worms?

    Thanks a million!


    • Bambi
    • July 29, 2013

    What are some of the “Bad Bugs” (for my Worm Compost) that I should be aware of?
    I have some bugs that sort of look like a cross between a Roly Poly and a flat grub (with legs). They are grayish in color and about a 1/2 inch long.
    ~I can actually HEAR them EATING!
    I’m worried because a friend of mine had the same thing happen and a week later, her worms were gone.

    • ben
    • August 22, 2013

    I too went away for 10 days and all the worms gone… it’s an outdoor worm inn.

    About 2x a week, I feed ~1lb of carrot/apple pulp, but the day before we left, I probably did about 2lbs..

    Still, it’s been HOT, so you would think the moisture of the pulp would have balanced out the heat..

    In short, aside from not going on vacation, what’s the recommended steps to take before/after leaving for a couple weeks?

    • Bentley
    • August 22, 2013

    BAMBI – what you’ve described sounds exactly like black soldier fly larvae (although they don’t have legs). While I’d likely avoid the term “bad” in association with most of the critters that can pop up in a vermicomposting system, BSFLs can be challenging, especially since they are often appearing when it’s already quite hot. They process wastes really quickly, likely increasing microbial activity (which also increases temps), and basically reduce habitat quality for the worms. One helpful strategy is to cut back on your feeding and instead to add lots of moistened bedding.
    BEN – that seems to be a common scenario. Hot temps + too much food + going away on vacation = increased chance of a mass die off. Yes moisture can be helpful IF we’re talking about a system that is very well ventilated. But moisture itself can actually amplify the effects of hot temps if there is not enough air flow (or if weather is very humid with little or no wind).
    What I would personally recommend before going away is add loads of bedding with a little food. I might also suggest setting up a very small “insurance bin” that could be kept indoors. This way you have a back-up stock of worms in case something goes wrong.

    • rik tiki
    • September 14, 2013

    Large area covered with decomposing wood chips. Worms by the thousands. I do not feed them. They vanished. Heartbroken.

    • Greg Dommert
    • December 8, 2013

    I think I have BSFL in my vermiculture bin. This past summer my wife suggested that I move the worms outside of her house….. I thought it was our house, anyways thats another discussion, right!! So I put them inside the Rabbit House which is an enclosed shed, good air ventilation. I had a tower about 5 stacks high and one day I layered the top bin with old bread. I looked in the bin several days later and the bread was moving and undulating. It looked like a horror flick scene. I lifted one of the pieces of bread, what was left of it and it seemed like thousands of maggots were under each piece of bread. in my research on this issue I came across articles and videos about the BSFL. I feel pretty certain that’s what I have but these larvae are white in color and what I have seen in videos looks chocolate in color. Could this be something other than BSFL? I emptied all of my worm trays into a recycled bathtub around the 1st of November and it appeared that the larvae were dead and the temps have been hovering around 45-50 dipping late at night into the 30’s. Now that everything is in the tub, it seems like the larvae have come back to life. It seems that I do have several hundred worms but not as many as I expected. I am doing Aquaponics so I am excited to have BSFL if that’s what it is. How well will the Red Wiggler and the BSFL coexist?

    • andrew
    • December 24, 2020

    Why don’t you make an researched article of why earthworm died of “string of pearl” ? a lot of ppl don’t know there such thing happened.. because a lot of worm died and rotted in the compost itself. If we don’t dig around we will most likely won’t see this suffering of worms.

    What happened ? when we put in raw food waste from kitchen, these happened to the worms.
    When we put in raw animal manure, be it from sheep or chicken.. the worm number reduced. Don’t tell me it is because the compost is heating up.. because it only heating up in the core of the pile, the outerside of the pile are perfectly good temperature for the cold winter..
    What’s the secret here ? to precompost the waste before feed to worm is the secret to success ?
    There is no such article in the internet , all being misled to “too dry, too wet, too hot, too cold…” all B.S. While there are the factors of course, but not the main important reason.

    • Bentley
    • December 28, 2020

    Hey Andrew
    For years I’ve suspected that what people refer to as “protein poisoning” (what leads to the string of pearls) is simply the result of excess nitrogen, which leads to ammonia release. This is a deadly toxic gas for worms, even in very small amounts. Adding raw manures – especially something like chicken manure – would absolutely expose the worms to ammonia, which is why I always recommend using well-aged material (in smaller home worm bins anyway – larger outdoor systems can easily have fresh stuff layered on top). You are right – this is something that isn’t discussed enough (although I have certain written about the hazards of ammonia gas plenty of times over the years)

    • Pam
    • January 28, 2021

    I did the same mistake: put in lots of scraps and some grass clippings before going away, weather was super hot on the long weekend and I came back to an empty worm bin. Stupid question – how do I know whether they died or just escaped? I had a LOT of worms prior to leaving (ie. spaghetti load lots) but now can’t see any. Dug around and didn’t seem to find any “bodies”. Do they just melt away? I have my fingers and toes crossed that they just escaped (I have an underground outdoor bin).

    • Cohen
    • March 13, 2021

    Hi I purchased some worms and I noticed a rove beetle on the top of the pile of worms. I discarded the beetle but I’m sure there are eggs or larvae in the worm pile somewhere. I read they are predators, should I be worried they’ll kill the red wrigglers? Thank you

    • Kevin
    • June 24, 2021

    This is all very interesting as it has also just happened to me. I’ve had the same family of worms for about 6 years now and they have been through a lot! as ive lived in many different places with different conditions but they’ve always seemed so resilient. Today, I went out to feed (worms are currently inside a school bus) and opened the lid and many flies flew out. Not very surprising as I did see some larvae last month. I went to mix up the bin expecting so see all my little friends and no matter where I dug I could hardly find any! And there was an incredible amount in there!! From reading this page, I can also support the theories that between HOT weather, flies, and even the smell of ammonia, I have lost most of my worms. Vanished. The pile was moister than expected but not compacted. Lots of both shredded paper and food waste.

    • Bentley
    • September 1, 2021

    Hi Kevin
    Hot weather – especially hot weather combined with fairly heavy feeding can be a MAJOR culprit when people are using outdoor systems. Even before the temps themselves become a hazard, just the extra warmth can accelerate the breakdown of the wastes, creating a richer, wetter environment – this can attract various types of flies, a prime example being Black Soldier Flies. Their larvae are MUCH more tolerant of hot, rich conditions so they really thrive, and further degrade the habitat for the worms. This plus temps that push past the worm tolerance threshold (somewhere around 94 F) creates a “perfect storm” of hazardous conditions and if the worms don’t have anywhere to escape to worms will start to die – which can create even more issues for the survivors. This is a big part of why I recommend use of systems that at least include some form of in-ground zone.

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