The Terro Fruit Fly Trap uses a liquid bait built around two key components: a vinegar-based attractant and sodium lauryl sulfate, a common surfactant (the same type of foaming agent found in shampoo and dish soap). Sodium lauryl sulfate makes up about 0.08% of the mixture by weight, with the rest being the vinegar solution itself. The product is classified as a 25(b) exempt pesticide, meaning the EPA considers its active ingredients low-risk enough to skip full federal registration.
How the Ingredients Work Together
The trap’s design is simple: lure the flies in, then drown them. The vinegar smell does the luring. Fruit flies are strongly attracted to the scent of fermentation, which signals ripening or decaying fruit. Apple cider vinegar and similar fermented liquids produce volatile compounds that fruit flies can detect from a distance, drawing them toward the trap opening.
Once flies land on the liquid surface, the sodium lauryl sulfate does the killing. Under normal conditions, water has enough surface tension for a tiny insect like a fruit fly to stand on it without sinking. Sodium lauryl sulfate is a surfactant, meaning it breaks that surface tension. When a fruit fly touches the liquid, it falls through and drowns instead of being able to walk across or escape. This is the same principle behind adding a drop of dish soap to a bowl of vinegar in a homemade trap.
What the Safety Data Tells You
The Terro Fruit Fly Trap (model T2500) carries a “Caution” signal word on its pesticide label, the lowest warning level. The bait’s oral toxicity is extremely low, with a lethal dose in lab testing so high (nearly 30,000 mg per kilogram of body weight in rats) that accidental ingestion of the small amount in a trap is unlikely to cause serious harm. For context, table salt is more acutely toxic by that measure.
That said, the liquid can irritate skin on prolonged contact and is more concerning for eyes. Terro’s related indoor fly trap product (T550), which uses a similar surfactant-based formula, carries warnings about serious eye damage and skin irritation. If the bait splashes into your eyes, rinse with water for at least 15 minutes. If swallowed, it may cause nausea, vomiting, or stomach irritation, but vomiting should not be induced. The formulation is not flammable.
How Long Each Trap Lasts
Each Terro Fruit Fly Trap stays active for up to 45 days. The package includes two traps, so used one at a time, you get roughly 90 days of coverage. You should replace a trap when it’s visibly full of flies or when the 45-day window is up, whichever comes first. Over time the vinegar scent fades as the volatile compounds evaporate, making the trap less effective even if it still contains liquid.
How It Compares to a Homemade Trap
The Terro trap essentially bottles the same chemistry as the most popular DIY fruit fly solution: vinegar plus a surfactant. A homemade version uses about a quarter cup of apple cider vinegar with a few drops of liquid dish soap in a jar. The dish soap serves the same role as sodium lauryl sulfate, breaking surface tension so flies sink and drown.
The main advantage of the commercial trap is the container design. Terro’s apple-shaped trap has a funnel-like opening that makes it easy for flies to enter but harder for them to escape, adding a physical trapping element on top of the drowning mechanism. A mason jar with plastic wrap poked with holes mimics this, but less elegantly. The bait chemistry itself is nearly identical. If you already have apple cider vinegar and dish soap at home, a DIY version costs essentially nothing and works on the same principle. Red wine with a few drops of dish soap also works well, since fruit flies are equally attracted to the fermentation compounds in wine.
Where the Terro trap has a practical edge is convenience and mess reduction. The sealed container is less likely to spill, doesn’t require setup, and looks less conspicuous on a kitchen counter than a jar covered in punctured plastic wrap.