Spraying for adult mosquitoes may be coming to DuPage preserves

In a move officials say could protect DuPage County against mosquito-borne illnesses, the forest preserve district may allow spraying to kill adult mosquitoes in its preserves on a case-by-case basis.

Forest preserve commissioners are reviewing a proposed mosquito management policy that outlines criteria that must be met before insecticides can be used to target adult mosquitoes on district land.

The existing policy, which was established in March 2000, allows for "adulticide" during a public health emergency. But that policy is vague, officials said, and the district never used insecticides to kill adult mosquitoes because those products also could kill other insects.

But with the emerging threat of illnesses such as the Zika virus, health department officials started working with the forest preserve several years ago to update the policy.

Tom Velat, the district's ecology coordinator, said that collaboration led to the new proposal.

"This gave us the opportunity to say more explicitly when those targeted applications will take place, under what circumstances and which diseases we would potentially be controlling," he said.

Criteria include conclusive surveillance data showing the source of target mosquitoes is on district land and that no other reasonable alternatives exist to protect public health. In addition, the insecticide "must be able to be delivered effectively to target specific areas of mosquito activity."

Velat said use of insecticides in preserves will be rare and a "last-resort option."

Meanwhile, the district will continue long-running efforts to control the Culex mosquito, which is the type known to carry the West Nile virus.

In addition to doing regular testing at preserves, the district does larvicide treatments when the bugs are found.

"If you have infected mosquitoes, you want to get them before they can bite people," Velat said.

Karen Ayala, executive director of the health department, said she's pleased with the proposed policy.

"The policy really takes into account the evolving and the emerging threats to public health from mosquitoes," she said.