A sugar-and-yeast bed bug trap works by producing carbon dioxide, the same gas you exhale, which is the primary signal bed bugs use to find a sleeping host. The trap is cheap to build (about a dollar in materials), takes 15 minutes to assemble, and can help you confirm whether bed bugs are present. It won’t eliminate an infestation on its own, but it’s a practical first step for detection.
Why Sugar and Yeast Attract Bed Bugs
When yeast ferments sugar in water, it releases a steady stream of carbon dioxide. Bed bugs navigate toward CO2 plumes the way mosquitoes do, treating the gas as a sign that a warm-blooded host is nearby and breathing. A resting adult exhales roughly 250 milliliters of CO2 per minute, and your trap mimics a fraction of that output. The CO2 drifts across the room, drawing bed bugs out of cracks and crevices toward the source.
Research from the Journal of Economic Entomology notes that competing with a living human requires a surprisingly high CO2 release rate, often more than what a person actually exhales. That means a yeast trap works best in rooms where nobody is sleeping, since a real person’s body heat, skin odors, and breath will outcompete the trap every time. If you want to monitor a guest room or confirm bugs in an empty apartment, the trap has a much better chance of catching something.
Materials You Need
- One 2-liter plastic soda bottle (empty and clean)
- 10 tablespoons of granulated sugar
- 2 tablespoons of active dry yeast
- 1.5 quarts of warm water (roughly 90 to 100°F, which feels warm but not hot to the touch)
- A shallow container like a plastic dog bowl, upturned Tupperware lid, or disposable pie tin, wider than the bottle’s base
- Masking tape or medical tape
- A light dusting of talcum powder or a thin layer of petroleum jelly
- Scissors or a box cutter
Step-by-Step Assembly
Cut the 2-liter bottle roughly one-third down from the top, just below where the curve straightens into the cylinder. You’ll end up with a funnel-shaped top piece and a taller bottom piece.
Pour the warm water into the bottom piece. Stir in the 10 tablespoons of sugar until it dissolves. Then sprinkle 2 tablespoons of active dry yeast on top of the water. Don’t stir the yeast in; let it sit on the surface so it activates gradually. Within 10 to 15 minutes you should see it start to foam, which means CO2 production has begun.
Flip the funnel piece upside down and nest it into the bottom piece so the bottle’s mouth points downward, creating a narrow opening for gas to escape. This concentrates the CO2 stream upward. If there are gaps between the two pieces, seal them loosely with tape so gas exits through the mouth rather than the sides.
Now place this assembled bottle in the center of your shallow container. The container acts as the actual pitfall trap. Wrap the outside of the shallow container with masking tape or cloth medical tape from bottom to top edge. This rough surface gives bed bugs traction to climb up and over the rim. On the inside of the container, apply a light coating of talcum powder or petroleum jelly so bugs that drop in can’t climb back out. Their feet grip rough surfaces well but slide on smooth, slippery ones.
Where to Place the Trap
Set the trap on the floor near the bed, couch, or wherever you suspect activity. Corners and along baseboards are natural travel paths for bed bugs. Place one trap per room for best coverage. If you’re testing multiple rooms, label each trap so you know exactly where any captures came from.
The trap performs best in a dark, quiet room with no people or pets present. Turn off lights and leave the room overnight. Bed bugs are most active between 1 a.m. and 5 a.m., so an overnight placement of at least 8 hours gives you the strongest results. Check the shallow container in the morning for trapped bugs. Adult bed bugs are flat, oval, reddish-brown, and about the size of an apple seed. Nymphs are smaller and nearly translucent.
How Long the Trap Lasts
A single batch of sugar and yeast produces usable CO2 for roughly 8 to 12 hours before the yeast exhausts its food supply or the fermentation slows. You’ll know it’s winding down when the foaming stops. For multi-night monitoring, dump the old mixture, rinse the bottle, and prepare a fresh batch each evening. Using water that’s too hot (above 110°F) kills the yeast immediately, and water that’s too cool (below 80°F) slows fermentation significantly, so aim for that warm-bath range of 90 to 100°F.
Downsides to Expect
Fermenting yeast produces a noticeable bread-like, slightly sour smell. In a small room with the door closed overnight, the odor can be strong by morning. If you leave the mixture sitting for more than a day without replacing it, mold can develop on the sugar water’s surface, adding a musty smell and potentially attracting fruit flies or gnats. Replace the mixture daily and rinse the bottle between uses to prevent this.
The bigger limitation is capture rate. Because the yeast produces far less CO2 than a sleeping person, and generates no body heat or skin chemicals, it’s a weaker signal. In rooms with a lot of airflow, clutter, or competing human odors (dirty laundry, bedding), the plume disperses before it reaches bugs hiding several feet away. A yeast trap is a reasonable detection tool, not a treatment method. If you find even one bug in the trap, you have confirmation of an infestation that needs professional attention.
How It Compares to Interceptor Traps
Passive interceptor traps, the kind you place under bed legs, work on a different principle. They don’t attract bugs with CO2. Instead, they physically block bed bugs from climbing up or down furniture legs by trapping them in a smooth-walled moat. The EPA recommends interceptors as part of an integrated pest management approach, alongside mattress encasements and regular inspection.
For most people dealing with a suspected infestation, using both types together gives you the best picture. Interceptors catch bugs that are already traveling to and from the bed. A yeast trap can lure bugs out of hiding spots farther from the bed, like baseboards, nightstands, or nearby furniture. Neither replaces professional treatment if you confirm live bugs, but the combination helps you understand the scope of the problem and whether treatment is working over time.