SLIDELL, La. (AP) — A Louisiana parish is bringing in a helicopter from Mississippi to fight West Nile virus this year.

A news release says the helicopter will drop anti-mosquito bacteria into a St. Tammany Parish neighborhood where one-fifth of the parish’s infected mosquito pools were found last year. Because mosquitoes are so small, groups of 50 or more of the same species are tested together for the virus.

The 30-day program with the helicopter will begin the third week of May in the Tammany Hills neighborhood.

The bacteria naturally infect larvae of mosquitoes and other flies. They’re a subspecies of Bt, or Bacillus thuringensis , which has been used since the 1960s to control plant pests. There are many strains of the bacteria, and each acts against different groups of insects.

“Treating mosquitoes by helicopter has been successfully used by several counties in Florida for many years,” St. Tammany Parish Mosquito Abatement director Kevin Caillouet said in the statement Friday. He said it has helped that region to keep Zika virus under control there.

The Mosquito Abatement team distributes larvicide into parish roadside ditches, but the helicopter can reach standing water that the team cannot easily get to. That includes unmaintained swimming pools, small ponds and water holding containers.

The helicopter can fly low and slow over a designated area, spraying the larvicide over habitats including woodlands and marshes.

Residents can expect a few low, loud passes near their homes, spraying a very fine mist over the area, officials said.

In addition, the helicopter will be added to the pesticide-spraying arsenal of ground spray trucks and Twin Otter fixed-wing aircraft for areas with increases in adult southern house mosquitoes, one of the main carriers of West Niile. Officials said the helicopter can focus on smaller areas than the airplane.

The helicopter contractor is Blackstar Helicopter of Picayune, Mississippi, which has operations across seven states.