Are Pineapple and Papaya Harmful to Worms?

I received an intriguing email recently from Janet Walker, who is a member of the Earthworm Interest Group of Southern Africa (a group I am now actually an ‘international member’ of), and a vermicomposting professional in South Africa. I asked if I could share what she wrote, and she happily obliged.

One of my worm clients recently came to see me at our Organic Market to tell me that she had gone on holiday having fed her worms well to make sure they did not starve. She was away for ten days, and on her return she did not find any worms in her system. On asking what she had fed to her worms, we have now discovered that leaving a WHOLE pineapple, cut in half, is a worm digester. I did not know that pineapple contains one of nature’s best digestive enzymes, as does papaya and the poor worms got completely digested.

This is really interesting, and not something I was familiar with. I know that pineapple is extremely acidic and have always basically considered it in the same category as citrus as far as adding it to worm bins goes (ie only in moderation). I have never heard of it completely wiping out a population of worms however, nor was I aware of the fact that it contains digestive enzymes. I have heard that Papaya can be good to eat with meats for this reason, but again haven’t really thought too much about the potential dangers of adding it to your worm bin – it definitely does make sense though!

Anyway, I will be curious to see if anyone else has experience with these two potentially-dangerous worm foods.

Thanks again to Janet for sharing this info with us!

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    • David
    • July 22, 2009

    Both pineapple and papaya (and pears, to a lesser degree) are excellent meat-tenderizers. I suspect that the enzymes involved are what killed and digested the worms. Cooking should denature the enzymes, though. A puree of any of the above makes a great quick marinade for beef short ribs or flank steak. I like one large or two small pears, several cloves of garlic, some fresh ginger and some soy sauce…yum.

    • Susan Bolman
    • July 22, 2009

    I’ve put lots of papaya in moderation over the last year and a half. What our local worm guru in Hawaii warned us of when starting is that while papaya and rind are fine, the seeds act as a birth control measure. She says they have a chemical that sterilizes the worms. I’ve never added the seeds. I’m not really interested in finding out for myself!

    My worms have always been able to get away from the papaya if they wanted and I haven’t noticed them doing so.

    I hear dead worms disintegrate pretty quickly. I wonder if it was the pH that did them in and then the local bin inhabitants got to enjoy the feast? I can see them all being unrecognizable after 10 days.

    • Jennifer S
    • July 22, 2009

    I have put whole pineapples in my bin without any negative side effects. I don’t eat papaya, but I have put both citrus and onion into my bins without problems. Onions do take forever to break down.

    My worms are rebels – they live in a plastic bin outdoors in Florida. They also get water added to the system now and then to help with evaporative cooling.

    • Bob Packard
    • July 22, 2009

    Oh, Oh! I think I see a new experiment about to start up.

    • Alan Lum
    • July 23, 2009

    Aloha form Hawaii! I put both types of fruit in my large bins. I age the fruit and add them without any hesitation. The pineapple bottoms and rough surface provide a nice environment for young worms. I often find worm balls under pineapple bottoms like you often fine under watermelon. As for papaya, I have heard about the seeds being birth control, however, my bins are thriving even though some seeds have been added.

    • Bentley
    • July 23, 2009

    Wow – thanks everyone for sharing your thoughts/experiences!

    • Mark in Santa Barbara
    • July 24, 2009

    I’ve heard that papaya seeds are somewhat effective as a human contraceptive, but I’d think the human and worm reproductive systems are so different that I’d be surprised if papaya seeds had a similar contraceptive effect in worms. Just guessing, though.

    • Kevin
    • July 25, 2009

    Contraceptive?Yikes. There’s something I wouldn’t count on! As for pineapple, it’s definitely an age-old kitchen fact (refugee from 20+ years in the food biz here) that if you try to cook with fresh pineapple, you best cook it well, to destroy those enzymes (almost all denature quickly in heat). e.g. any decent recipe for pineapple upside-down cake will either suggest canned and warn about how to use fresh – else you end up with a soupy pudding-like mess in your cast iron skillet. Easy to see how the proteins that make up a worms “skin” would be easily break down in this environment. Alan’s success must be attributed to the aging – hard to see how it would work otherwise – chemistry is chemistry, after all!

    • Sean in Plano, Texas
    • July 27, 2009

    I’ve added fresh pineapple scraps to my small population(100~ red worms) and slightly larger population(200~ red worms) and they seem to really enjoy the pineapple. Somehow I think the chemistry is a little more complex. Maybe the mucus coating of the worm protects them fairly well to where the enzymes aren’t too effective against them.

    • Will
    • July 28, 2009

    I make papaya smoothies all the time so it’s not unusual for me to stock up heavily on papaya and inevitably some of them rot before I can get to them. I’ve dumped two large whole papayas into my worm bin and the worms totally destroyed the papaya. I find it hard to believe that the worms were “digested”. Unless if that woman’s bin was just slightly larger than the pineapple itself it shouldn’t have killed off all the worms.

    Worms when they die degrade really fast so my guess is something else happened (like probably overfeeding with inadequate air circulation) that did the worms in.

    • Bentley
    • July 30, 2009

    Wow – this has turned out to be quite the hot topic!

    BOB- I think you might be right. Perhaps a pineapple/papaya challenge IS in order.

    • Andy
    • July 30, 2009

    Maybe someone was jealous of your worms and then stole them while you were on vacation….have any neighbors who like to fish?

    • Erica
    • July 31, 2009

    My worms are voracious with all fruits, but especially seem to love pineapple and melon, which we eat frequently.

    I now grind up my worm food, but for years just put in the pineapple rinds and hearts without aging them. The worms would often be found the next day happily (or so I think) huddled under the rinds, and would hang out there until the rinds were finished off. As with the rest of the family, for the worms pineapple is a favorite food.

    • Bay
    • October 27, 2009

    I recently conducted an experiment with worms. I fed one of my groups of worms tri-tip, and those worms I believe disintegrated unless they crawled out and are in my house. The other two groups did not disintegrate. One i fed lettuce, the other i fed paper. I’m just curious if worms can actually disintegrate.

    • Bentley
    • November 3, 2009

    ANDY – Definitely a possibility. Alternatively, one can also NEVER rule out alien abduction! Maybe ‘we are not alone’ in the realization of just how cool these worms are!
    ERICA – Very interesting. Thanks for chiming in
    BAY – What is “tri-tip”?

    • Bay
    • November 6, 2009

    Tri-tip is beef-steak. (Cooked).

    • Cecil Pearson
    • May 5, 2010

    I raise my worms in plastic containers with lids (have holes drilled in tops for ventilation). Worms were doing great! Then all of a sudden there are NO worms!. Bins are kept moist (water once per week as needed) and keep food available. Have had no problems at all. I did feed them pears early this week and now there are no worms!!!
    Any suggestions BEFORE I start again?

    • Steve
    • July 1, 2010

    I live in Phoenix, AZ. I found it difficult to keep worms in plastic containers wether in the garage or outside. It is hard to control the temperature with such high outside temps plus the heat created inside the bin. I have had great success by burying the plastic containers under a shady tree that blocks afternoon sun. May get some sun exposure in the morning hours. The dirt surrounding the bin helps to keep it cool from the 100+ temps. Just the shade alone might not be enough. Same goes for the garage. I drilled holes in the top and bottom. Drainage seeps into the ground, I’m sure the tree appreciates it. Be careful watering as bin drains slower being buried. Perhaps your bin got too hot.

    • Juliana
    • December 2, 2010

    PINEAPPLE IS A DEFINITE NO NO. Papaya seems fine though. Yesterday I fed my worms a whole pineapple that was already pretty well decomposed.

    I opened my worm bin today to find masses of worms trying to get as far away from the pineapple as they could. At first I was thrilled because I could see my entire population of worms – and there were many more than I could have hoped for. But then I began to wonder why they were crowding on the sides of my bin and realised that it must be that they were trying to get away from something.

    So I called my boyfriend for an emergency worm-saving operation and I dug around in the bin and removed as much of the pineapple as I could. I then sprinkled dirt over the top (as a way to neutralise the acid? any other ideas?) and then sprinkled some water over that and then ladelled my worms back on top.

    Any ideas for other ways to neutralize the pineapple acids? I’m rather worried about my worms now!

    • Dayna Mitchell
    • June 26, 2011

    I put straps of pineapple in my compost bin. There are clusters of worms feeding off the pineapple. Should I be concern about using my compose on vegetables, and what kind of worms are these that are in clusters?

  1. Hey Bentley,
    It’s been a while since I’ve talked to you, hope all is well your way. I know this is an old post here, but hopefully you will see this comment.

    I am making a video of composting a pineapple to see what happens. It should be interesting. I am thinking that at first the worms will avoid the pineapple, but hopefully sooner or later it will compost.
    In any case I was going to quote the top of this page and send a link back here to show where the quote came from. Thanks for all your insight over the years and for helping raise worm compost awareness.

  2. …so i want to know if i can feed papaya rind to my worms. i google it and here you all are. thank you. i guess i’ll go ahead and chuck it in…

    • Bentley
    • April 1, 2013

    OK – way behind with responses to this post. Sorry folks!
    Pineapple and papaya are both fine – just add them in moderation.

    MATTHEW – let me know how the experiment goes! Good to hear from you (but sorry for the lengthy delay responding).

    NOTE (to everyone reading this): E-mail is always a MUCH better way to reach me.

    • Freesia
    • April 11, 2013

    Pineapple totally wiped out my worms. They were doing fine, even the little ones seemed to be munching happily on the rinds. Then my teacher friend who is doing worm composting with her 5th grade class told me that pineapple is a no-no and could kill the worms. I dug out all the pineapple rinds, but it was too late. My worms were tele-transported into the land of disintegration. So sad. I will NEVER put pineapple in my new worm bin. Lesson learned

    • tamsey
    • September 9, 2013

    Pineapples kill worms and parasites.. they are eaten for this purpose by some people who may have parasitic infections. It is very effective.

    • Emily
    • January 3, 2014

    So what’s the consensus on this? MATTHEW WILSON, what happened with your expirament?

    • Wolf
    • June 19, 2014

    Hello Everybody
    Live in Costa Rica Highlands Temp day 20-30ºC and night 12-16ºC very stable all year round. Started up with about a 1000 worms in Feb in small plastic bin and 2 weeks ago I decided to split up the population in half…got very crowded in there…with all of castings, cocons, dirt and bacteria etc. New bin is a 55gal drum split in half and they are doing very well in the new inviroment. As start up bedding I used dirt 1/3 mixed with used coffee grounds 2/3·treated with EM and and left it sitting for a week to speed up breaking down before moving. End last week I fed them 2 big papayas cut in half the first time just as a try.Took out the seats etc…. to much moisture and put them face down. Same time I also fed them slurry of banana peel, slurry greens and a mix off egg shells with oatmeal.
    Resuming..there is a lot of choice on the menu. This was also the first time I tried large quantyties.
    After reading Your concerns about papaya it got me some how nervous. I opened up this morning for inspection and made the following observations. The meat of the papaya was more than half gone and lots of big worms crowded in the area….also the banana peel slurry same situation ….and lots of worms were I had put coffee grounds in a more concentrated way. The slurry with eggshell and oatmeal it seemed there are more smaller worms. The slurry from the vegetable leafs was the least affected.
    Another observation…the area with food rests from my first bin were deserted even so there is still plenty of food.
    Same situation in my old bin but due to less space less obvious.
    What I also observed….those guys are doin a lot better with more space and surface area of the bin. Since the barrel has a round shape the most humid and cold area is allways in the center and it gets dryer and warmer towards the upper outer edges.They do a lot of moving around and I think they some kind of find there own preferences for temp and humidity wich changes constantly.
    So I can not confirm Your concerns on papaya.
    Since I have tons of papaya here I will keep feeding them only in the bigger bin from now on, just to make shure.
    Should there be any negative evolution on the subject I will update

  3. I have been using lots of papaya with seeds in multiple worm bins with different species of worms for about a year. I have red wigglers and a native Florida composting worm. I have a very prolific papaya plant that I sometimes don’t get to all the fruit. I usually grind everything up in my Vitamix before adding it. The worms are definitely not sterile. Here is some papaya in action.

  4. Also, I just thought of this. Bromelain is the digestive enzyme in pineapple and that is mainly found in the core. I eat all the cores of my pineapples in smoothies so they never end up in the bins. I have used a ton papaya with seeds for sure and there must have been a fair share of pineapple without cores go in as well.

    • Ann Casement
    • February 8, 2015

    Wow! After reading this I went downstairs immediately to remove the WHOLE papaya I had put into my worm bin. When I picked it up, the worms appeared to be having a family reunion underneath AND INSIDE of the papaya, so I left it there. I believe in family!

    • Lani
    • April 30, 2015

    I just added a whole pineapple to my plastic bin. I was nervous because of the acidity and so stuck it in the corner so they could stay away if needed, and also stabbed it with some seashells – figured the acid from the fruit and the calcium of the shells might neutralize each other? 🙂 Today, two days later, I checked and there was a massive worm ball on top of the pineapple where I’d stabbed it with the shell, apparently happily feeding away. So, I’m going to leave it there for now since they seem happy.

    Also, I found this article about using vermicomposting to handle the abundant pineapple waste in Ghana. Granted, they are using native earthworms, but the composting process was highly successful and brought the ph back to neutral after 20 weeks:

    • Sue
    • February 23, 2019

    I have added pineapple to my worm farm on 3 different occasions and the following day there is always a feeding frenzy happening underneath! I don’t put the core in though just the outside! I recommend it my worms are huge now.

    • Lilli Keinaenen
    • August 5, 2020

    Found this thread googling whether or not I should give my worms pineapple. The second result was this university study!

    • Lilli Keinaenen
    • August 5, 2020

    From the study above:

    Therefore, this study focuses on the degradation of organic waste produced in the industrialized processing of pineapple waste (rinds, crowns and cores), which undergo a process of vermicomposting at a laboratory level. The methodology used included the pre-composting process and vermicomposting through Californian red worms using mixes tested in three di?erent proportions of pineapple waste (PR) and load material (LM) made up of vegetable waste and eggshells. Testing revealed that the pre-composting process for this waste was feasible as a ?rst stage of the degradation process; the characteristics of the pre-composted material allowed a favorable adaptation for both the worms and general degradation. It also showed e?ciencies in the removal of organic carbon between 36.40% and 45.78%. Results also showed the total nitrogen content remained between 1.2% and 2.2% and the carbon/nitrogen relation (C/N) had values under 20 as required for high-quality vermicompost.

    • Darren
    • October 31, 2020

    I just put pineapple into an outdoor rotten-log-pile composter I use today, so I wonder what will happen.

    An observation, my red wigglers (indoor bin) really like fresh Norfolk pine needles.

    A question: I am trying my hand at growing wasabi. Does everyone have any experience or ideas on worms and wasabi?

    • arfanh hossain
    • September 16, 2021

    i put papaya all the time because of my papaya farm they devour it very quickly but i haven’t given them rotting papaya those tae sour after few days basically my worms eat papaya most of the time some times banana but i have a question about ripe mangoes they like it but some ripe mangoes are sour in taste should i feed them those mangoes

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