PITTSFIELD — Onota Lake will be closed for recreation Tuesday, as city staff works with consultants to determine how to combat an emerging foe.

Jim McGrath, the city's natural resource program manager, said a recent study showed Onota has "a major problem" with European naiad, an invasive aquatic plant, in the northern portion of the lake.

The naiad was already on the city's radar — alongside milfoil, McGrath said — but is newly dominant in the lake. McGrath said chemicals typically used to fight the naiad also end up killing native species, which he's looking to minimize.

"We've always tried to seek a balanced approach," he said. "Our new data suggests that this balanced approach is even more critical now."

McGrath said lake treatment biologists from All Habitat will survey the lake Tuesday morning and will consult city staff and the Lake Onota Preservation Association regarding next steps.

If they decide to apply chemicals, McGrath said, it would happen midday Tuesday and would bar recreation on the lake until Wednesday morning.

Amanda Drane can be contacted at adrane@berkshireeagle.com, @amandadrane on Twitter, and 413-496-6296.