Daily News Archive

California Gears Up for West Nile
(Beyond Pesticides, September 30, 2003)
Bacteria pellets targeting mosquito larvae will be dropped in parts of Southern California this week in order to prevent the spread of West Nile virus (WNV). The action comes after a house sparrow was found dead from the virus in central Riverside, and after WNV was detected in chickens in the Coachella Valley and in a dead cow in Arcadia.

The bacteria pellets contain the biological pesticide B.t.i. (Bacillus thuringiensis var. israelensis). B.t.i. is a larvicide proven to be effective and has low levels of toxicity to humans and wildlife. Larvaciding allows control measures to be used in targeted areas, while mosquito larvae are still concentrated in breeding pools and before adult mosquitoes spread throughout the community. The Northwest Mosquito and Vector Control District plans to drop the B.t.i. on the ponds in the Prado Flood Control Basin, and along a half-mile stretch of river. It will be applied aerially because, according to officials, pesticides from trucks are not able to reach these areas. Jared Dever, public education specialist for the district, says the district will post signs along the river and make sure nobody is in the location being treated.

While the district is employing least-toxic methods such as mosquito larva-eating fish and larvacides, it has also fogged Mira Loma and Norco with adulticides, according to Dever. He stated that aerial treatments on this scale have not been done in five or six years. "Right now, we're willing to take pretty much any expense that we have to, in order to protect human health," he said. However, most people's immune systems are able to fight the virus. Only a small percentage of the population will get the virus, and "less than one percent of those infected with West Nile virus will develop severe illness," according to the Centers of Disease Control and Prevention (CDC). In the United States, people older than 50 years and those with weakened immune systems have the highest risk of severe encephalitis. Interestingly, this is the same population most at risk to pesticide poisoning.

Adulticiding programs spray pesticides indiscriminately and do not get at the mosquitoes until they have matured and are already nibbling at your skin. They also do little to restrict breeding. Mosquitoes develop resistance to chemical pesticides over time, which render the chemicals ineffective. Adulticides present considerable risk to all living things, and kill beneficial insects and natural mosquito predators, such as dragonflies, damselflies, and beetles. According to David Pimentel, Ph.D., an entomologist from Cornell University, close to 99.9 percent of the sprayed chemicals go off into the environment where they can have detrimental effects on public health ecosystems, leaving 0.10 percent to actually hit the target pest. ("Amounts of Pesticides Reaching Target Pests: Environmental Impacts and Ethics." Journal of Agricultural and Environmental Ethics Vol. 8, No. 1 (1995), pgs. 17-29).

Use of larvacides in Southern California is a step toward reducing mosquito populations without widespread spray of adulticides. Public education and monitoring of populations are two other important aspects of community mosquito management. One example of a progressive mosquito management policy is seen in Lynhurst, Ohio, which was covered in the July 14, 2003 edition of Daily News.

For more information, see Beyond Pesticides' West Nile Virus/Mosquito Management Program Page.