Aerial spraying for eight cities in Dallas County that opted for the insecticide spraying was completed Thursday night.
The effort targeted Rowlett, Sunnyvale, Seagoville, Wilmer, Ferris, Duncanville, Mesquite south of Interstate 30 and a small portion of Garland. All of the spraying was completed shortly before midnight, Dynamic Aviation tweeted.
In the news conference Wednesday, Dallas County Judge Clay Jenkins said all county residents should be aware that the aircraft would fly overhead to line up for the targeted areas. However, if aircraft are over non-spraying areas, it did not mean those areas were being targeted, he said.
People in non-spray areas also may see spray coming from planes overhead that is targeted for other areas. Because of offset, the spray would be released at a point that would allow it to reach the treeline in a different area, officials said.
For example, the offset on Monday night was 1.5 miles. Spray was released at a point where the wind would carry it 1.5 miles to the target. Clarke spokeswoman Laura McGowan said the aircraft uses computers and GPS devices that determine the plane's location and wind speed to determine when to release the spray so it reaches the desired target.
County leaders and mosquito control experts also said in the news conference that spraying is designed to lower infection rates but would not eliminate West Nile virus.
Ground spraying efforts by non-aerial spraying cities, as well as cities that have previously been sprayed by air, will also be under way this week.
NBC 5's Randy McIlwain contributed to this report.