BOISE, Idaho (AP) -- Herbicides are the most cost-effective way to fight invasive Eurasian milfoil, an official with the Idaho State Department of Agriculture says.

Lloyd Knight made the statement to the Joint Finance-Appropriations Committee Thursday as the state agency made a request to lawmakers for $900,000 for next year's budget in its ongoing battle with milfoil.

"To us, today, it's still our best tool available, to utilize herbicide first," said Knight, administrator of the Division of Plant Industries for the state agency.

Milfoil usually grows in water less than 20 feet deep and can eventually reach the surface, forming a dense layer that can entangle swimmers and hinder boats. Idaho and other states have spent millions trying to eradicate it.

The Spokesman-Review reports (http://bit.ly/VF6RMQ) the state agency requested this year that the funding next year be ongoing to cover various aspects of the milfoil battle happening mainly in northern Idaho. But Gov. C.L. "Butch" Otter has recommended another one-time allocation for next year.

Besides herbicides, other methods to thwart the advance of milfoil include divers pulling out the plant by hand, a method the state has used on smaller milfoil infestations in Priest Lake, around marinas in Lake Pend d'Oreille, and some areas around Cocolalla.

"In some of our smaller populations, we have utilized divers to hand-pull," Knight said. "What that allows us to do is survey and pull at the same time with divers. It can be fairly expensive, but it can be a useful tool with some of the smaller populations."

Knight said some areas of milfoil are tough to eradicate because of their location. One of those is under railroad and Highway 95 bridges outside Sandpoint. Herbicides don't work because of high water flows, which also make it not a safe location for divers. He also said the milfoil is located so far underwater that biological tools, such as milfoil-eating bugs, don't work.

"We're realizing we're going to have some areas where treatment is not going to be effective," he said.

Lawmakers were also concerned about the ongoing expense of fighting milfoil.

"It's my understanding that there really is no end in sight for that program," said Sen. Steve Vick, R-Dalton Gardens. "Do you think that's true, and do you think it should be part of your base budget if it's going to be ongoing?"

Celia Gould, director of the state agency, said she believed it would be an ongoing expense.

"There are some opportunities for us to eradicate in certain water bodies," she said. "Certainly in other water bodies where there's a swifter flow of water, the population is more dense, we're going to have to control through chemical means, hand-pull, whatever suits that particular water body."

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Information from: The Spokesman-Review, http://www.spokesman.com

Copyright 2013 The AP.