OLYMPIA — Citing a lack of documented evidence, the state Department of Agriculture has declined to restrict use of a class of pesticides implicated in the deaths of honey bees.

The department announced the decision Thursday following a 60-day review of a petition submitted by Thurston County commissioners. The county, at the request of county beekeepers, asked the department on April 8 to limit residential use of neonicotinoid pesticides used to kill aphids, weevils and other insects on ornamental plants. The insecticides also are used on crops, but limits on those uses were not requested.

Short of restricting the use of the pesticides, the agency committed to monitor ongoing studies and will urge federal regulators to consider whether additional restrictions are needed for backyard uses, the release said.

In a letter to county commissioners, Director Bud Hover said agency action against the common backyard pesticides is not appropriate at this time.

“There is currently no documented evidence that the use of the neonicotinoid insecticides on ornamental plants is causing a significant adverse effect on honey bee colony health in Washington state,” Hover wrote. “Because it has not been established that this use is a significant contributor to the decline of honey bee colonies in Thurston County or elsewhere in the state, the proposed use restrictions are not appropriate at this time.”

The European Union recently imposed a two-year ban on the neonics, as the products are commonly called, because of studies linking them to harm in bees.

But the Agriculture Department’s decision pointed to a federal review by the U.S. Department of Agriculture, the Environmental Protection Agency and pollinator experts last month. The review, the department news release said, concluded bee losses are the result of a number of factors, including parasites, disease, genetics, poor nutrition, as well as pesticide exposure.

Thursday’s announcement said the agency also will remind pesticide applicators of their responsibility to protect pollinators and assist retail groups in providing information to home and garden pesticide users.

The Thurston County request sought to bar most homeowners from purchasing neonicotinoid insecticides and require anyone using the products to obtain an applicator license from the state.