First reported 8/5/2010 4:46 p.m.
Thursday night, orange and white trucks with flashing yellow lights drove through Forest Park spraying a foggy mist from the back of their beds. That fog is what the Des Plaines Valley Mosquito Abatement District has determined is needed now as a precaution against West Nile virus.
“A very small quantity of pesticide is dispersed in the air in tiny droplets to control flying adult mosquitoes. … It is not necessary to stay indoors, though many people choose to do so. The U.S. EPA has registered the product for this use,” said Paul Geery, a biologist who manages the mosquito abatement district that includes the townships of Proviso, Oak Park, River Forest, Lyons and Riverside.
“Our district only does adult mosquito control when the risk of West Nile virus is significant,” Geery said.
By “significant,” Geery means that, of his office’s recent checks of traps throughout the district, an increase of positive readings was found – after a period of no positives – in the number of mosquitoes carrying the virus.
In Forest Park, for testing done the week that ended July 25, one of six mosquitoes trapped tested positive. For the week that ended Aug. 1, one of four mosquitoes trapped tested positive.
Decisions to spray in a community are made on increases in percentages in that community, and on test results from neighboring communities, Geery said.
The same night that Forest Park was sprayed for mosquitoes, so was River Forest. In that village, for testing done the week that ended July 25, one of seven mosquitoes trapped tested positive. For the week that ended Aug. 1, two of five mosquitoes trapped tested positive.
In Oak Park, spraying was scheduled for Tuesday night of this week. There, for testing done the week that ended July 25, one of seven mosquitoes trapped tested positive. For the week that ended Aug. 1, three of 20 mosquitoes trapped tested positive.
“Rainfall has something to do with what we’re seeing,” Geery said, “but mostly it’s heat. The higher the heat, the faster the virus goes through its cycle. The higher the heat, the faster mosquitoes go through their cycle.”
West Nile virus, a summertime threat in North America since 1999, mostly infects birds, but can hurt humans and escalate to encephalitis. It’s carried by adult mosquitoes.
The night before spraying was done in Forest Park, trucks were out in other communities in the Des Plaines Valley district, including Riverside, Brookfield and North Riverside.
