Does the scent of compost make bees angry?

I think I’ve stumbled upon a strange phenomenon: the smell released by turning compost pisses off bees. Yesterday was the third time this has happened to me. I took a sting just underneath my eye and another one to my right hand when I was turning a pile located about 15 feet away from a hive. Coincidentally, the same thing happened to a friend yesterday: he got stung while working with compost near a hive. Ordinarily our bees are reasonable about living in a small yard with humans–they are not even very aggressive when I open their hive. But apparently turning compost near them is a different matter.

I look like I’ve been in a fight. Lots of Benadryl today.

I have a theory. Bees are incredibly sensitive to odors and use them to communicate. Their alarm pheromones alert the hive to predators such as bears and people. Bee alarm pheromone consists of many different compounds. Interestingly, a lot of these compounds such as n-Butanol and Isoamyl acetate are byproducts of fermentation processes. I’m guessing that a number of these compounds are present in compost, and that when you turn a pile the act releases a cloud of compounds that mimic the bee’s alarm pheromones, causing them to attack.

It turns out that other lifeforms like to mimic honeybee alarm pheromone. Some species of orchids mimic bee alarm pheromone in order to attract pollination services. Small hive beetles, who raid beehives for their pollen, apparently bring with them a yeast that causes a fermentation process that mimics alarm pheromones. The small hive beetle’s fermented alarm pheromone, in turn, attracts more small hive beetles who quickly overwhelm the hive. These sorts of deceptive, symbiotic and parasitic loops in nature really amaze me. 

As a side note, I’ve only had compost pile related bee stings at this time of year, when honeybee numbers are at their peak and pollen and nectar sources are getting scarce (summer is hot and dry in Los Angeles and not much is blooming).

If you don’t have a hive, I doubt random, foraging worker bees would go after you if you are just turning compost in your yard. But if you’ve got a compost pile and are thinking about installing a hive–or vice versa–I’d seriously consider keeping the two as far apart as possible.

Am I alone in noticing this compost/bee alarm pheromone issue?

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30 Comments

  1. This is very interesting. I don’t have a hive but a few years ago some sort of bee built its home in my compost pile (may have been wasps, I didn’t stick around long enough to find out because they were ANGRY). I just left the pile alone that summer and turned it in late fall. They were gone by then. I’ve never had a repeat fortunately.

    • Bees often take up residence in those black compost bins cities like to give out. The Backwards Beekeepers, the local group I’m a part of, has done a lot of compost pile bee relocations.

    • I did a lot of Googling on this and did not find anyone else reporting this phenomenon. From my experience I wouldn’t put a compost pile next to a hive. Or, at least, I wouldn’t turn it at this time of year if it was near a hive.

  2. This spring we had yellow jackets build a ground nest right into the bottom of our compost pile. I could throw compost into the pile, but not do much else. I tried an organic repellent and a yellow jacket trap, but to no avail. They didn’t bother me, but my husband is allergic to stings, so, luckily for him, he couldn’t take out the compost! We have an animal or animals that visit our compost to see what’s tasty. One day the yellow jackets were just gone. We think that an animal visitor dug up the nest and ate them! We also have tiny little fly or bee-like things that congregate inside the compost bin – I was stung by one of them last year when I tossed in some compost. We rarely turn our compost, partly for these reasons.

  3. Bees respond poorly to large levels of carbon dioxide – funny that, what with most of their predators exhaling large quantities of carbon dioxide. This is why most beekeeping guides recommend against blowing on the bees to move them while doing hive inspections – if they become agitated they can follow that CO2 stream straight back to your face. Pretending there’s a forest fire by using a smoker is much less likely to get them chasing upstream to attack. I would guess the large quantities of CO2/CO/heat coming off a compost pile mimic the conditions of a large predator (particularly bears) and thus the bees go into defense mode. The fact that most compost is also dark in color doesn’t help either. Since European honey bees have evolved to defend against predators with heavy fur, they preferentially will go for eyes/nose as that’s where bears are most vulnerable.

  4. This has happened to me with a yellow jacket wasp. I was adding compost to the pile and was stung by two wasps who were nesting in the ground a few feet from the pile.

  5. The bright side of a bee sting to the face? All of the wrinkles around Erik’s right eye have vanished. He looks like a (pudgy) 20 year old on that half of his face. I think we’ve stumbled onto a real moneymaker: BACKWOODS BOTOX.

  6. Hahaha! That comment from Mrs. Homegrown is hysterical! This is good timing for this cautionary tale. I was thinking to set up my bees right behind my compost- the only area that is really free for bees.

    • Argh! Are you sure there’s nowhere else for the hive? They can go in small spaces. Like the side of the house, in a nook behind a shed or garage, or even on a roof…

    • Meant to add that we seem to be the only people on earth who’ve noticed this, so maybe it’s just a series of co-incidences? Or maybe it’s real, but very rare, a perfect storm sort of situation with just the right thing rotting in the pile. I’m interested to see if any confirmation rolls in. In the meanwhile, I wouldn’t want you to not get bees because of it.

  7. What a timely article! We’re having a beekeeping workshop with Kirk Anderson of Backwards Beekeepers at the Hathaway Ranch Museum in Santa Fe Springs today. I’ll be interested to hear what he and the other beekeepers there have to say about this! Seems like a useful thing for us new beekeepers to know about. Hope your eye feels better soon.

  8. Interesting. We have two compost piles (one hot, one cold) about 20 feet from the hive. In the four or so years we’ve had bees, I’ve never noticed a problem with the bees while working the compost. We also make wine at home, so our hot pile usually smells alcoholic.

    We do compost the leftovers from the solar wax melter into the hot compost. Bees will sometimes be hanging out near by for the next couple of days, but I’ve never noticed them to be aggressive.

    I did have someone in our community ask if it was safe to compost bananas near bees since the smell resembles an alarm pheromone. We don’t eat bananas, so maybe that’s a factor.

    • If you also make your own beer and have dogs, make sure to keep any hops residue out of the compost pile. It can poison your dogs.

  9. While a beesting can be like a shot of Botox, you might want to segregate banana peels and parts of apples, pears and kiwis, which may set off your bees.

  10. Funny I just posted on bee stings. We do this synchronized posting about once a year so I guess I should not be surprised by it anymore.

    http://www.backyardecosystem.com/backwards-beekeeping/happy-bees-equals-happy-beekeeper-how-treat-bee-stings/

    A couple of thoughts.
    1)There are several pictures on Backyard Ecosystem under both composting and beekeeping of a Nuc full of bees (strongest hive I have ever had, I could have made a fortune selling offspring of that queen) sitting on top of a compost bin. The bin is between two other compost piles one an open pile, the other a leaf mould pile, There is also a open plastic garbage can of weed tea. My other two hives are both within twenty feet. No stings, ever. So probably not a problem to have the bees nearby.

    2)I trust Erik when he identifies his perpetrator as a honeybee but often folks who are stung by “bees” are really experiencing wasps, hornets, or yellowjackets. I am especially suspicious when they are digging in soft ground like an compost pile which is a classic yellowjacket haven.

    3)In general a honeybee is not going to sting someone not standing in their flyway or in contact with the hive. Unlike many other similar insects honeybees die when they sting. If hive defense, being stepped on, or just bad luck in a collision on final approach is not the problem, then it probably was not a honeybee that stung you.

    4)Unlike Erik I am not so fanatical about my compost piles and they can easily go a month without a complete turning. I do tend to add fresh greens in the form of kitchen scraps right up till the next to last turn. So my mileage may vary.

    5)I would love to hear your thoughts and continuing reports. This may be a new area of exploration.

    6)What happens if we dip Erik in honey, and then roll him in compost, and then he turns the compost pile and opens the hive at the same time? Please don’t try this at home kids,this final point was intended as humor.

  11. Hm, interesting. My compost pile is about 30 feet from my hive, but I haven’t turned it since getting the hive. I have read that bees hate the smell of bananas and will get aggressive if they smell that, so it doesn’t seem illogical…

  12. Mr. Homegrown:

    Try a spit-poutice of plantain. If you get it slapped on the sting quickly, the redness will never materialize. Again: Plantago Lanceolata. Pick a leaf, chew it, slap it on the sting. Guaranteed. Trust Me, I’m a doctor.

    My best. Love your blog!
    Dr. Jon Ritz, ND
    http://www.drjonritz.com

  13. I have been stung 5 times this spring, in the past 2 weeks! I have lots of bees of several types, including honey bees and I have a big garden with flowers and vegetables and fruit trees. There’s always something for the bees starting in early spring. I’ve been in the same place for 21 years. I’m not afraid of bees at all. I have always been able to go out and water, dead head, harvest, just do what needs to be done, along with bees buzzing all around me collecting their nectar. All goes well. —-That is until now! I go out, and in no time bam!- I’m stung while watering. Everything is the same as far as what is growing out there, and all, but I may have an answer. The only thing I can think of is that yesterday, when I was stung twice within a half hour, in different parts of the garden, is that earlier in the day, I was shoveling mushroom compost which is full of steer manure. I was standing in the stuff while shoveling it. Possibly the last time I was stung a couple of weeks ago, I may have been shoveling the same stuff that day too. Could it be that the oder of this mushroom compost on me makes the bees think I am a animal and thus a threat to them, and so they stung me??? I sure hope that was the case, so I can go back to a peaceful gardening routine. (Today, no mushroom shoveling, and I went out and deadheaded flowers with my arms in the bushes clipping off spent flowers while bees were whirling around me every where, and no incidents of stinging.

    • Interesting. I was stung last week for no reason I could figure –they really went after me, got in my hair–yikes!–but now that I think of it, I was spreading steer manure that day. I know for sure they don’t like it when we work with our compost pile. (That’s why I leave that for Erik to do! ;) ) But maybe the steer manure has some chemical trigger, too.

  14. Hot days , physical exertion leading to sweat being produced A red flag for bees!
    Think back many thousands of years when our ancestors were less fragrant than today and depended on occasional raidings of bee hives to supplement their erratic diet. An association with, a genetic imprint must have been developed in the species. Plus the fact that fast and hard movements such as turning a compost heap could be conceived as a potentially threatening act. Oddly enough here in South Africa I have found that bees, the cape bee (Apis mellifera capensis) get really uptight when black workers are busy in gardens in their proximity, due to the fact that they, the workers,tend to perspire much more than caucasians and trigger the alarm bells leading to sprints out of the greenery. Try pruning trees another big no no for Apis, They Hate with a passion the exhaust (and ) noise of a petrol driven chain saw. I as a Caucasian have in the event of such initiated attacks only once been targeted.Lucky so far. Our bees seem much more aggressive than the European species, a furry gentle insect. I have found that one can move ones hands between plants when deadheading flowers without even disturbing the bees as long as the movements are slow & gentle.
    Happy gardening.

  15. I’m very excited to have found this thread. I live in the forest of Scotts Valley in Northern California. This year I discovered this bee pattern after I amended my garden with a mixture of steer manure and OSH soil+compost mix. So far I’ve amended my soil twice and have noticed several bees start swarming the amended soil areas.

    • I just went to a workshop with apiculturlist Michael Thiele. I asked him about this very problem and he reminded me that bees are a “big nose.” They are very sensitive to smell.

  16. I have my Hive about 2 meters from my compost heap and have absolutely no problems! I deliberately placed my Hive there for a couple of reasons, one being to include them as part of my ‘family’ (which they are). Any time I go near the Hive or to the compost or veggie garden beds there, as I get closer to the hive I start to talk to them. The guards pop out to check if its really me and then they get on with their day flying around me. Maybe its time to develop a different relationship with our bees? More inclusive. I have absolutely no fear of my bees at all. I love being around them, though I’m sensible and respectful.

  17. I just got attacked by bees after turning my compost pile. I noticed a wet “rotting” spot in my pile. It smelled kinda bad when I turned it up. Within a minute or two, a bee landed on my hand and stung me. That is when I noticed the bees flying all around me. I ran like a madman as a few chased me thru the yard and into the house, where I found another bee on my shirt.
    I do have a large natural bee hive in a tree about 30 feet away from my compost pile. They are normally very docile. I can walk right up to the hive and watch them without any problems. I am puzzled by the attack. It must have been that smell that pissed them off. I turn the pile regularly without any problems. I just added a bunch of produce into the pile and wet it down a couple of days prior. Today is the first time I noticed any anaerobic smells coming from my pile. It had to be the cause.
    The bees were still flying around and chasing me after 20 minutes every time I went back outside. Now I am stuck in the house waiting for the sun to go down. Has anyone else had this problem?

    • I have this problem all the time. I put my pile too close to my normally docile bees. I did some research on this issue and the smell of compost is very close to the alarm pheromone the bees use to signal each other that there is a predator nearby (their predators, by the way are we humans and bears). I’d suggest moving your compost pile or turning it when the bees are not active such as when it’s starting to get dark, early in the morning or on a cold day.

  18. I would find it very unlikely that they are honey bees. I have hives in my backyard and the bees come down in the spring. They love coffee grounds and anything else they can forage on. As spring gets warmer only a few come around and by summer no bees at all. Also it would seem unlikely the swarm would go to a compost bin. Queens don’t go without a swarm. They are probably bumblebees or some sort of wasp. Just be thankful you have pollinators around and do your composting early in the morning or in the late evening. It may be difficult for you but as we are losing pollinators all over its the least you can do for Mother Nature.

    • Hey Albert–it’s not a swarm–they are guard bees that come check me out when I turn the compost. Definitely honey bees. I’m going to move the compost pile so it doesn’t bother them.

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