DALLAS (AP) The first aerial spraying of insecticides in the Dallas area since the 1960s is set for this week in the battle against the worst outbreak of West Nile virus in the nation so far this year.

An official with the company hired to spray for mosquitoes in Dallas County says at least two planes will be in position by Thursday evening. Several cities have approved aerial spraying. Dallas officials haven't decided.

Clarke spokeswoman Laura McGowan said Tuesday that the chemical, synthetic pyrethroid (py-REE-throid), will be spread in small amounts and is safe for residents.

Truck spraying continued in Dallas County, where 10 deaths have been attributed to West Nile virus this year.

Dallas County had aerial spraying in 1966 for an encephalitis outbreak blamed for more than a dozen deaths.