Information that is given to the public on the efficacy of pesticide application to fend off viruses such as West Nile Virus is limited. We are told about studies and given numbers but what is the transparency of the study? Who completed this study? Is testing done in a limited scope? Are the tests done in real world conditions? How often has this test been done and where? And most importantly, what are the long term effects on the health of humanity, animals, pollinating insects and our planet? It is imperative that we question the solution to a problem. If it causes more harm than good, then we must keep searching for a comprehensive and intelligent solution that will serve the higher good of all. Read on…
Why Pesticide Spraying for West Nile Virus in California May Cause More Harm Than Good
“There’s not enough evidence that all this spraying has changed the dynamic of the outbreak, and that’s in part because the studies really haven’t been done to find out.”
-Michael Hansen, the chief pesticide researcher at Consumers Union, which publishes Consumer Reports magazine, Newsday, November 7, 200032
Effectiveness of Spraying in Controlling Mosquito Populations is Limited
One study conducted by the Connecticut Agricultural Experiment Station in 2002 found that mosquito populations did not drop notably after trucks sprayed pesticides in the cities of Greenwich and Stamford.33 However, very few studies have been conducted to document the effectiveness—or lack of effectiveness of pesticide spraying in curbing mosquito populations under real word conditions.
Most studies on the impact of pesticide spraying are performed under out-door “lab” type conditions. In such studies, caged mosquitoes are placed at measured distances from spraying, at differing pesticide potencies. Some cage trap experiments in residential areas have shown a reduction in mosquito populations of about 30 percent after a spraying.34
Such studies, however, may overestimate the effectiveness of spraying since they do not take into account the many variables that are involved in ground spraying. Real world mosquitoes are not trapped in one place. Rather, they can hide under leaves and in vegetation. As a result, extrapolating the efficacy numbers from cage or trap studies to actual spraying programs is questionable.
“In order to work, the insecticide must hit the mosquito directly,” Cornell University researcher Dr. David Pimentel reported in a November 2000 interview with Newsday. “But since spray trucks are only fogging the street side of buildings, I doubt that more than one-tenth of 1 percent of the poison is actually hitting its target. And you have to put out a lot of material to get that one-tenth of a percent onto the mosquito.”35
In a 1998 study, it took two to three times more insecticide to kill 90% of the mosquitoes in residential settings than it took to kill 90% of the mosquitoes in open areas. Spraying high enough levels of insecticide to kill most of the mosquitoes in residential areas would require violating current labeling safety guidelines.39
33. Christine Woodside, “No Big Fall in Mosquitoes After Communities Spray,” New York Times, 6 October 2002, 14CN.
34. Dan Fagin, “Doubts about Spraying — Some Experts Call it Ineffective Against West Nile Virus,” Newsday, 8 November 2000.
35. Dan Fagin, “Doubts about Spraying — Some Experts Call it Ineffective Against West Nile Virus,” Newsday, 8 November 2000.
39. Gary Mount, “A Critical Review of Ultralow-Volume Aerosols of Insecticide,” Journal of the American Mosquito Control Association, 14(3):305-334, 1998.