One Vinegar Trap Does Not Clear a Fruit Fly Outbreak: A Growth-and-Capture Disproof for Kitchens

The vinegar trap is the standard household response to fruit flies, usually deployed singly. This study tests the claim that one trap clears a kitchen outbreak, modelling 60 starting adults, a population doubling time of 6 days at 25 C while a breeding site remains, a trap capture zone of 1.2 m radius removing 18 percent of adults inside it per day, and a 14 m2 kitchen zone. With the breeding site present, one trap leaves 143.6 adults after 14 days — the outbreak more than doubles under treatment. Two traps leave 65.4, roughly standing still; three leave 28.4. Removing the breeding site reverses everything: with no breeding, one trap plus natural mortality leaves 3.8 adults after 14 days, and two traps leave 1.4. The claim therefore fails, and it fails for an instructive reason: capture subtracts a fraction while breeding multiplies the whole, so the trap can never outrun an active site inside its owner's kitchen. The originated rule is to find and remove the breeding site first, then use traps as a mop-up and monitor, at which point one or two suffice. This study is simulated, not measured. SIMULATED, NOT MEASURED.