INDIANAPOLIS (AP) — A fast-growing vine that's left parts of Indiana beneath tangles of greenery is coming under assault as the state ramps up its efforts to kill the leafy invader.

Over the next few weeks, contractors hired by the Indiana Department of Natural Resources will begin spraying herbicides on 32 tracts of kudzu vines in 17 Indiana counties.

The effort is Indiana's most ambitious step yet in a campaign that began in 2006 against kudzu, which threatens to kill native plants and trees beneath its dense woody vines and leaves.

An even greater concern is its ability to harbor the crop-killing Asian soybean rust.

Ken Cote, a DNR nursery inspector, said the agency hopes it can control the state's kudzu infestations before they become the sort of ever-expanding menace that plagues Southern states.

"It's now or never. If it keeps spreading it's going to become such a problem that we're never going to be able to get a handle on it," he said.

But killing kudzu isn't easy. Cote said kudzu plants have large root systems that can survive having their energy-collecting leaves killed by a herbicide. Eradicating a single kudzu patch means spraying it every year for three to five years.

As of May, kudzu patches covered at least 110 acres of Indiana landscape, with most of the 36 counties with confirmed infestations in the state's southern half. Eighty-eight percent of those 109 sites were less than 2 acres, but Cote said some are nearly 10 acres in size.

To date, the DNR has spent about $18,000 on kudzu eradication, but Cote said that fully eradicating Indiana's kudzu patches would take millions of dollars and years of effort.

With the state's current budget limits, he said the DNR hopes to contain Indiana's kudzu patches until a sustained effort can be mounted to eliminate the Asian plant that grew out of control after it was planted in many Southern states in the 1930s as erosion control.

Cote said it's unclear how kudzu ended up in Indiana but it could have arrived in dirt or hay bales brought in from infested areas.

Some kudzu tracts in Brown County have been growing for about 50 years, and Cote said that in the counties along the Ohio River he's found kudzu vines that are 4 inches across and have climbed some 60 feet into trees.

"There are sites that are so thick you can't walk through them unless you have a machete," he said.

Because kudzu is related to soybeans, it's also prone to the same diseases. That includes Asian soybean rust, which can kill or stunt the growth of soybeans, lowering yields.

Soybean rust was found on soybean plants in Indiana late in the 2006 and 2007 growing seasons, but it appeared too late those years to have any economic impact on the state's soybean industry, said Kiersten Wise, an assistant professor of plant pathology at Purdue University.

The fungus has so far not showed up in the Midwest this summer because it has been confined to the Deep South, said Wise, a specialist in field diseases.

Glenn Nice, a weed scientist with Purdue's extension service, said kudzu worries soybean farmers because if a patch of kudzu is near a field infected with soybean rust, it could allow the fungus to re-infect that field even after it is treated with a fungicide.

"If someone is spraying to control soybean rust and they have kudzu close at hand, it could allow that rust to come back to their field," he said.

Aside from the DNR's efforts, the U.S. Department of Agriculture is also trying to combat kudzu infestations.

Over the last three years, Indiana farmers have received $262,000 from the USDA's Natural Resource Conservation Service to combat kudzu, autumn olive, Asian bush honeysuckle and five other invasive species, said agency spokesman Mike McGovern in Indianapolis.