IDEAL, Ga. — It’s only a few months into the cotton growing season, but already the budding rows of cotton are dwarfed by towering weeds that starve them of sunlight, nutrients and water.

This pesky pigweed species, called palmer amaranth, has long been held in check by powerful herbicides.

But three years ago, scientists discovered a far-from-ideal development in this central Georgia farming hamlet: The first species that’s resistant to all but the most aggressive chemical treatments.

Now, this powerful new breed has spread to farms throughout the Southeast and is threatening to move further west, baffling farmers and bringing comparisons to that deadliest scourge of cotton.

“We’ve mowed down many thousands of acres of cotton,” sighed Stanley Culpepper, a University of Georgia weed specialist, as he plucked a particularly tall weed. “Since the boll weevil, there’s been no pest as challenging as this one — without a doubt.”

In Georgia alone, researchers expect to find it in about 40 counties this year. It’s steadily spread throughout the Southeast, afflicting farms in the Carolinas, Tennessee and Arkansas. With each farm it devastates, it’s brought comparisons to the boll weevil, the beetle that lays eggs in the plant’s boll and ruins them.

“You tend to exaggerate whatever is hot at the moment,” said Alan York, a weed science specialist at North Carolina State University. “But having said that, this is a bear. It’s resistant. It’s very prolific. It grows very fast. It’s very competitive — and it’s relatively hard to control to start with.”

Farmers have indeed found a formidable foe in the palmer amaranth, which crowds out cotton plants with stalks that can grow eight feet tall. For one thing, the plant is productive. Each female produces as many as 500,000 seedlings, meaning just one plant can birth an entire field.

Unlike other pests, pigweed can continue to grow an inch a day even without water, making it particularly adept during the epic drought gripping the region. It also thrives in hot weather, continuing to grow when temperatures top 90 degrees and other plants shut down.

“It’s happy as it can be when other crops are suffering,” said York. “It simply outcompetes other weeds.”

Much of the pigweed plants were held at bay by cheap herbicides deployed by farmers from Virginia to California. But only the most aggressive and expensive chemical treatments have worked against the resistant variety, and even those hardly manage to contain them.

Even handpicking isn’t foolproof. The weed has the mind-boggling tendency to grow back if the top is chopped off or if any point of the root is touching the ground.

“An old Mennonite farmer told me there’s always going to be thorns and thistles,” said Gordon Sutton, a 74-year-old who owns the Ideal farm where the new breed was first discovered. “You control one thing, and another crops up. Crabgrass was our biggest nemesis for years. And now it’s pigweed.”

There are no estimates yet on the scourge’s economic impact, but scientists estimate untold thousands of acres of cotton — worth millions of dollars — have been plowed under. And York said it could cost $20 an acre to fend off much of the plant, costing the industry millions more.

Jay Griffin, 52, who owns a 700-acre farm in nearby Oglethorpe, said he’s lost hundreds of acres of cotton totaling more than $150,000 to resistant pigweed since it first popped up on his property five years ago.

“It’s the worst I’ve ever seen. I’ve been doing this for 35 years and it’s just as bad as the boll weevil,” said Griffin. “You can’t plant cotton like we used to. It’s resistant to just about everything. You can throw everything at it you want to, but you ain’t going to kill it.”

To Culpepper, it’s a frustrating — and sometimes hopeless — battle.

He quickly set up an experiment station in Ideal and seven other plots throughout Georgia after the herbicide-resistant plant cropped up here. But even when fields are sprayed with 25 times the normal amount of herbicide, there are still signs of pigweed poking out.

With the next era of chemicals not likely to be commercially ready until 2013, Culpepper is focusing on teaching farmers about the threat. At lectures to groups in 17 states, he sounds more like a high school health teacher than a weed specialist, telling them the only proven method to stop the weed is prevention.

“This field started with one or two plants, and now it’s across 500 acres,” said Culpepper, waving his hands over the field of pigweed. “If a single pigweed plant is allowed to germinate, it can spread 500,000 seeds across the land. The game is over.”