Fairfax County officials are expecting this year's inchworm epidemic to be so widespread that they're launching an aerial attack against them.

For the first time in a decade, the county plans to bring in a helicopter to drop pesticides on the worms, which experts fear are killing maple, hickory and oak trees and foliage.

The project will take place on 2,000 acres near Franconia and Mount Vernon and cost $200,000. Officials will then follow up the aerial attack with a second, $26,000 effort on 200 acres from the ground.

"It's also a huge nuisance issue," said Troy Shaw, coordinator of the county's Forest Pest Management Program. "They're often seen hanging down from trees on silk, invading people's homes ... in addition to killing trees."

The worms' threat to public safety and foliage ultimately forced the county Board of Supervisors to order Tuesday the preparation for the two efforts, expected to take place about April.

Shaw said the pesticides aren't generally harmful to humans or pets but cautioned that the helicopters cannot instantly turn off the spray when flying over neighborhoods.

He urged homeowners who may be outside at the time of the spray to quickly wash off the chemicals should they be unable to find shelter when the helicopter is overhead.

The bacterium used, Bacillus thuringiensis, may not be harmless to other, less noxious insects in the area, however. Shaw said butterflies and larvae that live on or eat the leaves where the substance is dumped might be in danger, too.

This concerns Mount Vernon resident Ned Stone, who lives in the spraying area. Stone said he hasn't seen many inchworms -- or inchworm damage -- on his property in recent years.

"Insects are part of the circle of life," Stone said. "I think we should do nothing until we really have a problem. I haven't seen a real problem."

Huntington resident Alan Ruof also said he hasn't seen much damage over the years.

"It seems to me that individuals could take the necessary actions themselves," he said. "I'm glad I'm not the one making the decision."

Fairfax County's campaign against inchworms is unmatched in the region. Arlington County, Alexandria and Maryland have not taken action against inchworms.

An aerial spray is used to combat gypsy moths in Maryland, but Prince George's County hasn't been sprayed in more than a decade and Montgomery County has not since 2009.

"Most homeowners have [the worms] and don't even realize it," said Fairfax Supervisor Jeff McKay, D-Lee. "We know there's a problem. It's better to be safe than sorry. The damage they can do to trees is a really serious issue."

Residents in the affected areas will receive two letters with more information about the exact date and time of the spray as it nears.