NEW ORLEANS (AP) — Eight years into a U.S. program to control damage from feral pigs, the invasive animals with big appetites and snouts that uproot anything that smells good are still a multibillion-dollar plague on farmers, wildlife and the environment.

These prolific hogs gone wild have been wiped out in 11 of the 41 states where they were reported in 2014 or 2015, and there are fewer in parts of the other 30.

But despite more than $100 million in federal money, an estimated 6 million to 9 million feral swine still ravage the landscape nationwide. They tear up planted fields, wallowing out huge bare depressions. They out-eat deer and turkeys — and also eat turkey eggs and even fawns. They carry parasites and disease and pollute streams and rivers with their feces.

Total U.S. damages are estimated at a minimum $2.5 billion a year.

Adam McLendon, whose family farms about 8,000 acres of peanuts, corn and cotton in several counties in southwestern Georgia, estimates feral pigs have cost them more than $100,000 a year for the past 15 years.

That’s about what one of Mississippi’s two levee boards pays each year to trap and kill feral hogs and to repair damage from their rooting, commissioner Hank Burdine estimated. “That is nominal compared to what we would have if we didn’t take care of it and had a flood,” he added.

Near the Red River in north Texas, hogs are so hard on corn that Layne Chapman and his neighbors no longer even try to grow it.

“I can remember the first day someone called me and said, `You’ve got a pig in your wheat field,’ and I said, ’No we don’t have pigs.’ That was in 2006,” Chapman said. He stopped planting corn in 2016.

The animals root out rows of freshly planted peanuts and corn, leaving huge ruts that must be smoothed before the field can be replanted — weeks after the best planting time. Hogs return to cornfields when the crop is ripening, trampling stalks, taking bites out of ears and wallowing to cool their sweatless bodies.

The U.S. Department of Agriculture’s National Feral Swine Damage Management Program has received $31.5 million since it began in 2014.

McLendon and Chapman, who continues to grow cotton and wheat and to raise cattle on about 8,000 acres in Vernon, Texas, have both benefited from pilot eradication projects under $75 million allocated separately by Congress in the 2018 Farm Bill.

Research also continues on ways to poison feral hogs without killing other animals, said Michael Marlow, assistant manager of the USDA program. The poison, sodium nitrite, is a preservative in bacon but keeps the blood of live pigs from carrying oxygen.

Trials this coming winter and spring will test whether birds can be kept away from dropped bait by using a less crumbly formulation, along with grates to keep crumbs out of reach and air-powered “scarymen” like air dancers used for store advertising, Marlow said.

But for now, two major control methods are aerial shooting and remote-controlled traps that send cellphone pictures when a hog sounder is inside.

Some states have legalized night hunting for feral swine. Derek Chisum, who grows peanuts, cotton and wheat in Hydro, Oklahoma, figures he has killed 120 to 150 a year since Oklahoma did so three years ago.

Since 2014, Idaho, New York, New Jersey, Maryland, Maine, Colorado, Iowa, Minnesota, Washington, Wisconsin and Vermont have killed their small populations of feral pigs, though the program is still keeping a wary eye out in the last six states.

The worst-hit states — California, Oklahoma, Texas and Florida, where a runway collision with a pair of wild pigs totaled an F-16 fighter jet in 1988 — are still at the program’s highest level, with more than 750,000 hogs. Arkansas, Louisiana, Mississippi, Alabama, Georgia, North Carolina and South Carolina put their populations at 100,000 to 750,000, though Hawaii has moved a level down.

The Texas population overall has been “fairly stable” at roughly 3 million since 2011, said Mike Bodenchuk, state director for USDA’s Animal and Plant Health Inspection Service, or APHIS.

But statewide reduction, let alone eradication, is likely to be a long slog with tools and money available now, he said in a telephone interview.

Researchers are still trying to get good numbers for populations and damages. The current estimate of at least $2.5 billion in annual national damages is up $1 billion from the 2014 estimate, and the number of pigs is now estimated at 6 million to 9 million rather than 5 million.