As Loudoun County officials continue their efforts to combat the spread of Lyme disease, which is transmitted through the bite of an infected black-legged tick, environmental activists have again voiced concerns over the use of an insecticide spray in public parks.

The spraying was first done last year, when nine county parks were treated to reduce the tick population. The spraying alarmed environmental activists and beekeepers, who feared that the insecticide could be harmful to foraging bees and wildlife.

This year, six county parks were initially targeted for spraying: Claude Moore Park, Franklin Park, Philip A. Bolen Memorial Park, Conklin Park, Brambleton West Fields and Banshee Reeks Nature Preserve.

The plan again drew sharp responses from environmental advocates. On June 10, the Loudoun Wildlife Conservancy wrote a letter to the county Board of Supervisors to express concern about the spraying, particularly at Banshee Reeks, a preserve recently certified as a monarch butterfly way station and a healthy habitat through the Audubon at Home program, said Nicole Hamilton, conservancy president.

“It’s not even necessarily just about the wildlife,” Hamilton said in an interview. “It’s about human life. The board, by putting out a contract to spray, is essentially sending a message to the public in general that spraying is good. And spraying is not good.”

The preserve will be spared, at least for now. David Goodfriend of the county Department of Health said the county decided not to spray at Banshee Reeks after realizing the preserve’s certifications might be threatened.

The five other parks would be sprayed, Goodfriend said, “on a more limited scale than what was done last year, focusing on trail areas and some edge areas, where it’s more likely that people could come into contact with the woods.”

The spraying of Talstar, which is a bifenthrin-based insecticide, is one of several measures identified in the county’s 10-point action plan to fight Lyme disease. The plan was established in March 2012, when the Board of Supervisors voted unanimously to declare 2012 “Lyme Disease Awareness Year” in Loudoun. The board also established the Loudoun Lyme Disease Commission, which was charged with implementing the plan.

According to the federal Centers for Disease Control and Prevention, Loudoun has among the highest rates of Lyme infection in the nation, and the highest rate among Virginia jurisdictions. Many of the county’s heavily populated neighborhoods are surrounded by rural farmland or wooded parks, an ideal environment for an illness that thrives in areas where ticks can be easily transferred from wildlife to human hosts.

More than 200 cases of Lyme disease were reported in Loudoun last year. The number could be higher, because many cases are unreported or misdiagnosed, health officials said.

Hamilton said Thursday that the Loudoun Wildlife Conservancy had not been notified of the change of plans regarding Banshee Reeks. The wildlife conservancy was “very happy” that the preserve would not be sprayed, she said. But her concern about the other parks remained.

“It’s been shown that the best approach to minimize Lyme disease infection is to deal with it personally: spray your clothing, do a tick check. That’s the number one thing to do,” she said. “Spraying offers a false sense of security, and it’s making other people rise up and say, ‘Let’s spray in our neighborhoods; let’s spray in our back yards.’ ”

Hamilton said she hoped for answers to questions included in the organization’s letter: What kind of evaluation would be conducted to determine the effects of the spraying, positive or negative? How were these parks identified as the best places to spray? What evidence is there that spraying would reduce Lyme infection?

Goodfriend said there was no easy way to assess the effect of the spraying, in part because the use of the pesticide was so targeted.

“It’s only one application, and ticks will come back because we’re not saturating the park with pesticides,” he said. “If we went back again to measure next year, the ticks would be back.”

He echoed Hamilton’s assertion that personal protection was by far the most effective step residents can take: “That’s the message that we keep conveying to people — to dress appropriately, to use insect repellant.”

The parks sprayed this year were selected in the spring, Goodfriend said, after an environmental company determined the highest risk areas, “based on tick habitat, human use, and areas where humans and ticks may come into contact.”

County spokeswoman Anna Nissinen said the spraying was done in “the most efficient, effective and environmentally sensitive manner” possible.

An online Lyme awareness survey launched this year will help officials determine where infected residents think they were exposed, whether in parks, along community trails or in their back yards, Goodfriend said. The results of the survey could help shape future plans for spraying.

Hamilton, who said her organization was still awaiting a response to its letter, said she wants to avoid an “adversarial dynamic” with the county board. “I just want to find a way to have this discussion [about spraying] and say, ‘Here is what we would recommend,’ ” she said.

The Loudoun Wildlife Conservancy asked to be a part of the Loudoun Lyme Disease Commission when the group was first formed, Hamilton said, but the request was declined.

“If we can help, we’d like to. It’s just a matter of them wanting to listen to us,” she said. “The environment really is public health. You can’t divorce the two.”