In areas that mosquito-spraying does not occur, many homeowners might hire a company themselves. In North Carolina, there are three viruses that are carried by mosquitos: La Crosse encephalitis virus, West Nile virus, and Eastern equine encephalitis virus. To combat the diseases and the mosquitos that carry them, the homeowners could hire a private company to apply barrier sprays around their homes. These sprays are applied to vegetation and are useful for lowering the numbers of mosquitos for a few weeks—depending on the weather.
In the study Evaluation of Barrier Sprays for Controlling Mosquitoes in Eastern North Carolina: Can Land Cover and Spatial Analyses Improve Predictions of Efficacy? the researchers sought to uncover whether the type of spray used had an effect on mosquito control as well as the potential relationship between the environment and increased mosquito populations.
The effect of barrier sprays
The study conducted in the North Carolina neighborhood applied Bifen Insecticide (bifen) and Suspend Polyzone (deltamethrin) as well as utilized an area that was not sprayed for their control. Using CDC light traps, they collected mosquitos from these areas over a 6-month span, beginning two weeks before the barrier sprays were applied.
While there was not a major difference in the number of mosquitos collected in the two weeks before the first barrier sprays were applied, the number collected was drastically higher in control and deltamethrin treated areas when compared to the bifenthrin treated areas. Mid-June had the highest number of mosquitos collected during the entire study and was the only time a high-number of mosquitos were caught in the traps.
Interestingly, the treated and control areas in the northern section of the neighborhood showed little variance in the numbers of adult mosquitos collected. The southern section, however, showed a significant difference with much higher trap counts in the controlled areas when compared to the treated areas.
Variance of mosquito populations
Overall, the study found that Bifen IT had substantially reduced the abundunce of adult mosquitos when compared to the control areas. Suspend Polyzone also caused a significant reduction when compared to control, but not as drastic when compared to the Bifen IT results.
During the study, a hot spot was observed in the southwest area as well as a section in the center of the neighborhood. The researchers concluded that this was due to environmental differences between the two treated areas.
In this study, we see that yes, barrier spray treatments work to lower the number of mosquitoes in an area. However, we can also see how great the difference in mosquito pressure can be even within one neighborhood. These differences reinforce the need for integrated pest management, including source reduction of breeding sites, mosquito traps, and wearing personal repellent when you are outside. In pest control, it is often the addition of lots of little factors that can reduce your overall risk of being bitten.