In the United States alone, we spend more than $2.5 billion a year trying to rid our homes of cockroaches and other pests—but a new study says some of us may be doing it all wrong. The peer-reviewed study tested the effectiveness of baits, gels laden with insecticide, and bug bombs, devices that “fog” a room with an insect-killing aerosol. For at least one pest, the common German cockroach (Blattella germanica), bombs don’t work, says the study, but baits do.
Scientists set off four kinds of bombs and placed two kinds of baits in 30 infested homes in Raleigh. Twenty homes got one of the four bombs and 10 got one of the two baits. The scientists counted the number of cockroaches before treatment and after, once at 2 weeks and once 1 month later. In every home that had been bombed, cockroach numbers stayed the same, the researchers report this week in BMC Public Health. With one bait, populations dropped by more than half after 2 weeks; with the other, they plummeted by more than 75%. Numbers went down even more after the full month.
Researchers also tested the amount of insecticide residue left behind by the bombs. Even before the treatments, the middles of countertops, floors, and other areas heavily trafficked by humans (but not bugs) had residue; just hours after bomb use, those levels shot up 600%. Some residue stuck around even a month later.
Baits cost more, but given the ineffectiveness of the bombs, the researchers say they are still the best option. As for bombs, the researchers call them “inappropriate” for home pest control, going so far as to question whether they should still be sold for this use.