Study summary
Efficacy of Two Pyrethroid Insecticides Applied as Barrier Treatments for Managing Mosquito Populations in Suburban Residential Properties
Trout RT, Brown GC, Potter MF, Hubbard JL
Read the original paper- Study type
- Field Trial
- Year
- 2007
- Published in
- Journal of Medical Entomology (2007), 44(3):470, PMID 17547233
- Evidence strength
- Well-supported evidence
Summary
Barrier sprays are the other main way people treat an area rather than their skin: a pest-control operator sprays a residual pyrethroid onto the shrubs, low vegetation, and shaded resting spots around a yard, so mosquitoes that rest there pick up a lethal dose. This suburban field study tested two of these pyrethroids, lambda-cyhalothrin and bifenthrin, on real residential properties and measured how much they cut human biting compared with untreated control yards. It is directly relevant to anyone weighing a professional yard-spray service.
Key findings
Both barrier treatments sharply reduced biting from the Asian tiger mosquito, Aedes albopictus, which rests in the low vegetation the sprays hit. Lambda-cyhalothrin cut biting by about 89.5 percent and bifenthrin by about 85.1 percent compared with untreated controls. But the study also carries a crucial honest caveat: Culex mosquitoes, the group most tied to West Nile virus, were not significantly reduced by either spray. The researchers attributed this to biology, since Culex tend to rest higher up and away from the treated low vegetation. The buyer lesson is that a barrier spray can strongly knock back the daytime, low-resting tiger mosquitoes while doing little against Culex.
Limitations
The strong knockdowns applied specifically to Aedes albopictus, and the same treatments failed to significantly reduce Culex, so a barrier spray is not an all-mosquitoes solution. These are residual insecticides applied broadly to yard vegetation, which raises real questions about non-target effects on pollinators and other insects that this trial was not designed to weigh. Results reflect specific products, application methods, and one suburban setting, and effectiveness against a species depends heavily on whether that species actually rests where the spray lands.