The Health Department plans to close South Philly's FDR Park at dusk tomorrow night so crews can spray to control the mosquito population.

Weather permitting, crews with truck-mounted sprayers will disperse fine aerosol droplets of Anvil 10-10, a product that has no residual effects and evaporates quickly into the atmosphere. The mist stays aloft and kills mosquitoes on contact. The area to be sprayed is bounded by Broad Street, Pattison Avenue, 26th Street and Interstate 95.

Samples taken by the Health Department in the area have shown adult mosquito populations that can carry the West Nile virus, which can cause West Nile encephalitis, an infection that can result in an inflammation of the brain. There have been no confirmed human cases of West Nile virus in Pennsylvania this year.

For more information about West Nile virus and the state's surveillance and control program, go to www.westnile.state.pa.us. For questions on the West Nile virus program in Philadelphia, call 215-685-9000. - Inquirer staff