Bed Bugs: Lures

In general, you cannot solve a bed bug problem by attracting and trapping bugs: there are simply too many bugs that are breeding ahead of their losses. We had (presumably) brought very few bugs home in our luggage, so every one we trapped was one less bug in the room. In any event, the number of bugs caught in the traps would give some idea of how much trouble we were in.

The bottom line: we trapped one or two bed bug instars and no adults.

Anything labeled for use against bed bugs carries a staggering markup and considerable smoke-and-mirrors marketing, but if you go back to the original sources (see the references in the first post), you’ll find out what actually works, which is quite different from what’s advertised.

The study by Wang, et. al., tested carbon dioxide, heat, and chemical lures. Tested singly: CO2 is pretty good, heat is OK, chemical lures definitely come in last. Basically, I think there are way too many significant figures in their results, but under idealized test conditions in a small arena, they collected about 80% of the bugs after six hours.

One key number: the CO2 flow rate was about 170 ml/min, roughly that produced by an adult human.

Another interesting number:

The visual inspections found ≤23 bed bugs in each apartment and they were considered as low levels of infestations.

CO2 mug and powder trap
CO2 mug and powder trap

Based on that, we decided to build some CO2 traps, which led to those observations. Our version of a dry-ice trap used a huge insulated mug filled with dry ice, perched atop an inverted dog food dish. We deployed two traps like that.

The dog dish has a cloth skirt (so the bed bugs can get traction on the way in) and a layer of talcum powder inside (so they can’t get any traction on the way out). The gas flow rate was in the right ballpark.

After several days, we had collected exactly zero bed bugs.

That wasn’t surprising, of course, because we knew we didn’t have all that many bugs, but we were still getting bitten in other parts of the house. Like, alas, the guest-room bed where we’d moved after gutting our bedroom.

Using dry ice as a CO2 source is relatively expensive and exceedingly inconvenient. We went through two iterations and decided that this was far too expensive, given the expected results.

It turns out that baker’s yeast metabolizes sugar into ethanol and carbon dioxide as the yeast gradually dies in a sea of dilute ethanol; if you have a distillation rig handy, you can probably get a decent yield of vodka from this project. Normally I use the carbon dioxide to stretch bread dough, but in this case it came in handy all by itself.

You can buy, for $50, a Bed Bug Beacon or you can build your own carbon dioxide lure and trap from ordinary household items for pretty close to zero dollars. Your choice.

I built and deployed four yeast reactor lures, built from gallon milk jugs and Tygon tubing from the parts heap. This picture tells you pretty nearly everything you need to know.

Yeast CO2 generator
Yeast CO2 generator

I used a hollow punch to poke those the neat holes in the lids, but a razor knife will suffice. Seal the opening on the bottle cap with something sticky; nothing adheres well to polyethlyene and Tygon, although the contact cement I got with the dryer rear seal worked well.

Cap detail
Cap detail

Put three quarts / liters of warm water in the jug, add a cup of sugar (lots of sugar = longer production = more gas) and a teaspoon of yeast (lots of yeast = more production = live hard, die young), put on a solid cap, and shake vigorously to mix. Swap in the cap with the tubing and deploy. The recipe is totally non-critical and would make a great science fair project…

The dingus on the other end of the hose is the bottom of a cottage cheese container, artfully sculpted into a shallow dish with four small feet between low arched openings. Basically, it’s a little cover to trap the CO2 in a confined area and let it leak out in relatively concentrated streams. I have no idea if that’s how it works, but it was easy to do and keeps the hose from wandering away.

What they don’t tell you is that the gas production from a small yeast reactor is maybe 5%, tops, of the 150-200 ml/min required to mimic a human: I bubbled the gas into an inverted 60 ml syringe and used a stopwatch. The gas production varies strongly with time; after a week it’s down to essentially zero, so I’d say the “11 day” claims for the BBB’s lifetime are, mmmm, fanciful, at best.

Gas production is proportional to the total number of active yeast. Methinks a cup of sugar in three quarts of water will yield more yeast than a packet of sugar in, what, a pint jar? If you drop fifty bucks on a BBB, make some measurements and let me know, OK?

Maybe they use brewer’s yeast, which is an ethanol-tolerant strain of ordinary baker’s yeast. The end product, after a week, smells strongly of ethanol, so I’m not sure how much difference that would make.

In any event, my opinion is that such a minimal gas flow can attract bugs from only a very limited radius, so the results are far less conclusive than dry ice or pressurized-gas lures. Of course, if you have floors crowded with bed bugs, a few of them will stumble across the lure simply by accident.

Of course, there is one lure that’s absolutely guaranteed to attract bed bugs from across the room: you. I’ll discuss that after covering traps and barriers…

27 thoughts on “Bed Bugs: Lures

  1. As a homebrewer, I love the idea of using a reactor to generate CO2. I find the whole cheese container thing odd since CO2 is heavier than air and should leak out fairly quickly from that cup. In any case, I have a few suggestions for the next reactor.

    First, use invert sugar instead of a plain sucrose solution. Yeast has a harder time digesting straight-up sucrose, although it does work. Creating invert sugar is easy: put saturated white table sugar in water on a stove and stir until boiling. It’ll turn into a slightly off-yellow clear saturated sugar solution via hydrolysis. Let it cool before adding to the yeast solution (most brewing yeast prefer 65-70F). Some invert sugar brewing references ask for citric acid or to use a raw sugar, but that’s more for flavoring and brewing technique than as yeast food.

    Second, follow up on your instinct and use a brewers yeast. Select a wine or cider yeast (they’re often the same strain) if you’re after a strong, vigorous reaction. Beer yeasts will work well but don’t peak as hard as wine yeast. Reaction time will be about a week with the strongest activity in the first 4-5 days. Larger vessels (5 gallons) will take about 24 hours to kick into gear.

    Lastly, save the sludge that accumulates at the bottom of the vessel in a sealed test tube and put it in the refrigerator. That sludge is yeast that you can save for later! Yeast purity is a concern for brewers, but that’s not a big deal here since this project is just for CO2 reactions and not taste. Reuse that yeast several times over before getting a fresh batch. This technique will significantly extend the life of that $2 yeast packet.

    1. I find the whole cheese container thing odd since CO2 is heavier than air and should leak out fairly quickly from that cup.

      That’s the whole point: the bugs navigate upstream to the source, so you must provide a nice source for them. I’m not convinced the inverted-cup thing works, but the commercial version does something similar… probably for a similar reason: just to keep the hose under control.

      The gas flow rate remains the real dealbreaker: I’m not convinced a yeast reactor generates enough gas to actually attract any bugs, at least for relatively low infestation levels.

      One of these days, I should do the experiment on gas volume vs yeast type vs sugar type vs lifetime… but I really hope I can’t add “vs bug attraction” to that matrix.

      This technique will significantly extend the life of that $2 yeast packet.

      Ah, but we do a lot of baking: I buy yeast in two-pound lots. A teaspoon or ten of yeast for the reactors didn’t make much of a dent in our supply.

      And having all that baking yeast on hand gave me no motivation to get anything different, particularly given my overall reservations on how effective it would be.

      I thought the sludge was dead yeast. Glad to know that’s not true: our septic tank is certainly overjoyed by now.

      Thanks for the details; they’ll come in handy for somebody!

  2. They have these CO2 tanks for paintball or at Lowe’s for air powered tools. They generally cost little to refill, but I don’t know how long they would last,

    1. I considered those, but couldn’t crack the problem of metering the flow to a trickle without buying a stack of plumbing. The yeast reactors were the Hobson’s Choice solution: not very good, easy to do, and cheap enough to deploy in several rooms.

      Should this situation ever come up again, I’ll probably spring for the compressed gas solution…

  3. Can you realistically dial in 170 ml/min with a standard 0-500 PSI pressure regulator on a 2000 PSI tank? What kind of PSI delta would yield that flow rate? I guess I need to dig out an old chem textbook.

    One thing that scares me about using compressed gas is the potential for asphyxiation, in the event of failure or an incorrect setup. Small quantities of yeast is a lot safer, in that regard. At the very least, I’d opt for a high quality pressure regulator, as opposed to a home made contraption.

    I’m really interested in combining this with a simple battery-powered heater, consisting of a power source and a static resistive load. I hear what you’re saying about lures, but I’m hopeful that the proper temperature & CO2 flow rate would prove to be an effective bug magnet.

    1. dial in 170 ml/min with a standard 0-500 PSI pressure regulator

      Not even on a low-caffeine morning!

      As nearly as I can tell, they used a two-stage regulator and a needle valve. I’d lay long odds that there’s a flow meter in there, somewhere, too, at least until they got the right valve settings. The tank looked to be paintball-gun sized, rather than a hulking K or T tank that you’d find in a welding setup.

      And, despite my DIY perversion, I’m solidly behind the notion of not building a high-pressure gas regulator. That’s easy to do in mass production and hard to do as a one-off gadget.

      a simple battery-powered heater

      I doubt you’ll get enough energy out of a battery to make that work. You’re fighting CO2‘s enthalpy of vaporization in the tank plus its adiabatic expansion in the valving: a hulking industrial chiller yanked that energy out and you’re not going to replace it from some piddly battery.

      A wall wart is your friend…

      1. I was actually thinking of a wall wart, but didn’t want to get into that level of detail.

        Now that I’ve seen a MSDS on CO2, I’m even more uncomfortable with the prospect of opening a high-pressure source in my home! This phrase kind of jumps out at me:

        High concentrations of this gas can also cause an oxygen-deficient environment. However, the asphyxiating properties of Carbon Dioxide will be reached before oxygen-deficiency is a factor.

        1. Yeah, and you get dumb a lot sooner than you keel over, too. Makes recovering from mistakes a whole lot harder than you’d expect.

          A friend has a horror story of hearing a series of loud crashes in a lab. Turns out a K-sized gas cylinder fell over, broke its valve stem against a bench on the way down, then punched through two concrete block walls before stopping. It was pretty well encased in frost by the time he saw it…

          I’d like to know the ethanol concentration when the yeast keels over, but not enough to actually buy a hydrometer. Although the brewmaker charts indicate just a few percent, that sauce smells rather potent…

          1. I was wondering your thought on utilizing CO2 with a regulator. I have a Milwaukee Instruments CO2 Regulator that I currently use on my other obsession (before bed bugs!) of keeping live plants in aquaria.

            I have a 5# CO2 cylinder that is connected to the regulator. Connected to this is a needle valve the I can fine tune down to less than air bubble per second.

            I was wondering if I used this set up to create multiple CO2 traps (using a manifold). Would you have any input to the rate of CO2 I would need to output to attract the bed bugs?

            I can easily create 8 CO2 traps from this devise and even with the use of a solenoid valve and timer have the CO2 traps active only at night.

            I live in a small 900 square foot apartment, so minus items like walls and halls I could have 1 C02 trap for every 100 sq feet.


            1. any input to the rate of CO2 I would need to output to attract the bed bugs

              Just as it says in the post, the traps described by that original research used 170 ml/min; follow the links back to the paper. Apparently heating the gas helps a bit, but getting it up to room temperature would be close enough.

              In my case, gallon-jug yeast reactors cannot produce that flow rate, at least long term, which is why I think they’re bogus. If you have enough of an infestation to catch bugs in a yeast reactor trap, the CO2 gas probably doesn’t have much to do with it.

              Maybe you can do better with a CO2 tank, but the flow rate will be much higher than a few bubbles/minute!

              Good luck!

  4. How about shutting off the electricity in the late fall for 24 hours and leave a warm trap in the center of each room so they go into it as their only heat source? While I sleep in my car that night.

    1. Nope, they’re not nearly as vulnerable as we’d like them to be: they can survive far lower temperatures than your house will reach and not all of them will find the lure. They tend to move toward warmer spots, but that means they’ll move down into the foundation as the upper levels cool…

      The real problem is that you must kill all of the critters, because one egg-laying female will repopulate your house in short order.

      1. How about the heat source has adjustable BTU output( like a lightbulb with a dimmer switch). Initially I would heat the whole room and with a thermal camera I can measure the radius of the heat output and incrementally and slowly lure them into the very center?
        Maybe someone will come up with a ray gun that penetrates walls and sweep the wholw house with it.?
        Maybe I can sleep in a bug zapping cage so when they go after me they will all roast?
        Do you have hope that mankind will find a solution? Everything has a weak spot and I like to believe that humans are smarter and can defeat them.

        1. incrementally and slowly lure them into the very center?

          The problem: not all of them will respond to any lure.

          That means you never know when you’re finished; remember, we never saw an adult bed bug during any of our adventures.

          Everything has a weak spot

          And I think they’ve found ours… [sigh]

  5. With having two cats and two people in our home, there is an ever constant source of food with the cats. Having tried DE and heat gun sweeps 2x a week, I feel like we are only containing an explosion instead of winning the battle.

    Sound frequency devices had zero effect on any level. Spray on contact, again, it is only a contain solution. Duct tape between rooms has caught 2 bugs in 3 weeks….

    In fact, I feel like fresh food when doing the bi-weekly deep clean…..

    I really like the research here and would like to hopefully contribute some good news. I’d like to grow it in maybe having 4 gallons filling a right side up dixie cup.

    Can partial water changes/added sugar keep a more constant flow of gas perhaps?

    Anyone consider kaboocha? It is a symbiotic yeast/bacteria which would support reuse. It looks like a floating mushroom making it easy to reuse…..

    1. For all the reasons cited in the post, I think CO2 lures are a waste of time and money. In the case of yeast generators, they’re also totally ineffective because the gas flow is pitifully low. Given a choice between you and a gas generator, the bug’s choice is clear…

      Also, you won’t get anywhere waving a heat gun around; they only heat the surface for a brief moment and simply force the bugs deeper into their cracks (if they notice you at all).

      Basically, when you have a serious infestation, DIY solutions probably won’t work and, if you’re at the point where you’re actually catching bedbugs, then you have a serious infestation.

      Good luck!

  6. What do you think is the best approach if exceeding DIY?

    Kinda bummed at your reaction as you were the first to speak my language…engineering…. LOL. It happens!

    For those considering heat guns,there was a distinct smell of burning flesh when heating the carpet where my hampers are kept moving the recommended 1in/sec. (I work in medical and know the smell of burning flesh from a harmonic scalpel and the carpet is less than one year old). The scent was not present in any other area. POSSIBLE CONCLUSION: The bugs like the smell of dirty laundry and yes, I do work out to a sweat. It *is* possible that something from my wicker hampers was in the carpet, too. Less than a year. My gut still says it wasn’t burnt old sweat but burnt flesh.

    In trying to re-use your date of producing 60ml with 1 gallon of water/yeast/sugar, what was the rate?

    For my first experiment, I wish to make something more attractive than a cat so I don’t need to send them off until this issue is solved. I want them to live in the hardwood areas only until our home is our home again. They are naturally are no longer using the sofa and prefer wood surfaces up high. I think a trap beside the sofa could be setup to be more attractive than a cat….

    My first experiment will be 4 gallons of yeast/sugar/water going into a right side up 16 oz. cup with sweaty workout underwear inside the cup for free pheromones. Paper towels are climbable on the outside to dispose of the whole thing in an incinerator.

    Please let me know if you recommend any data. I’m a bit focused on the end result….

    1. the best approach if exceeding DIY?

      That’s when you call in the professionals and just spend the money like you had it. The longer you wait, the more bed bugs you have, the harder it is to get rid of them. What you’re doing now isn’t working, so it’s time to move on.

      The bugs like the smell of dirty laundry

      As nearly as I can tell, they aim for body heat and, secondarily, carbon dioxide; everything else is lost in the roundoff. Look at the study: everything other than heat isn’t really relevant.

      what was the rate?

      I don’t have a number, but it was many bubbles/minute at the start, tapering off regular bubbles, then nearly nothing in short order.

      A 1 mm diameter bubble is about 0.0005 ml, so you’d need 2000 of them to get 1 ml: you need 340 thousand bubbles per minute to get enough gas. That just doesn’t happen with yeast and sugar: you can’t produce enough of a gas that only somewhat attracts the bugs. This is not a winning combination… unless you’re selling little packets of yeast and sugar at a tremendous markup, that is. [sigh]

    2. I’m too lazy to go back and find a citation, but when I was doing the research for my little adventure, the data showed that bedbugs Simply Will Not dine on cats. If they’re eating your cats, they’re not bedbugs, as far as I understand it… (there are plenty of other critters in this world, Horatio.)

  7. Hey there,

    You mentioned that “the gas production from a small yeast reactor is maybe 5%, tops, of the 150-200 ml/min required to mimic a human.”

    If so, what are your thoughts on building 10+ reactors that produce twice as much gas as the above-mentioned “small yeast reactor”?

    1. thoughts on building 10+ reactors

      I think it’s a waste of time that allows the bugs to continue breeding.

      The only study I’ve found suggests that bed bugs are mildly interested in a concentrated source of CO2. A dozen weak sources doesn’t equal one concentrated source, so the bugs see them as an blanket of gas, not a point source that resembles supper.

      The flow rate isn’t constant, either, because yeast works great at the start, has a moderately broad peak, and tails off rapidly.

      And, once again, the bottom line: you can’t trap enough bed bugs to remove an infestation. Traps may be useful to get an idea of the scale of the problem, but they’re not going to reduce the population enough to matter.

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