ELK GROVE, Calif. -- A fresh wave of aerial spraying against mosquitoes that may be carrying West Nile virus started Wednesday evening in parts of south Sacramento and Elk Grove.

About 23,000 acres in the Pocket and Florin areas of south Sacramento, along with Elk Grove, will be treated in the coming days, the Sacramento-Yolo Mosquito and Vector Control District said.

Spraying will take place Wednesday, Thursday and Friday from about 8 p.m. to midnight each day. Treatments may be delayed if winds are too strong.

David Brown, manager of the district, said officials have noticed a surge in West Nile virus a few weeks earlier this summer compared to last year.

"We've seen in increase in West Nile virus in both our mosquito population as well as in our bird population," Brown said Wednesday.

The spraying will take place from Elder Creek Road to Elk Grove Boulevard, as well as in the Pocket area and 2.4 miles east to the railroad line.

The district said the areas will be treated with Evergreen 60-6, an insecticide approved for use in mosquito control by the Environmental Protection Agency.

Brown added that swimming pools at foreclosed homes are often not being maintained, resulting in a prime breeding ground for mosquitoes.

"The opportunity for mosquito production within our urban areas has greatly increased," Brown added.

The district is asking local residents to get rid of standing water where mosquitoes may breed.