OKLAHOMA CITY (Reuters) - Oklahoma’s legislature has passed a bill aimed at reducing the state’s bulging population of feral hogs, blamed for spreading disease and wiping out crops, that would let people kill them without a hunting license. A study by an agricultural research organization found that the animals are running wild in all of Oklahoma’s 77 counties and could number as high as 1.6 million, which would be one of the highest feral hog populations of any state. The measure, passed on Thursday by the Republican-led legislature, would permit hunters to kill hogs without a hunting permit on their property or on someone else’s property with the landowner’s permission. It also would allow use of night-vision equipment to hunt them. Republican Governor Mary Fallin’s office has not said whether she will sign it into law. “This legislation gives Oklahomans more options to combat the rapidly growing feral hog population,” said Republican state Representative Sean Robert, a bill co-sponsor. The most effective method of eradicating the wild hogs currently is aerial shooting from helicopters, state officials said. “Feral hogs wreak havoc on Oklahoma’s farms, ranches and ecosystems, and cost farmers, ranchers and landowners,” said Tom Buchanan, president of the Oklahoma Farm Bureau, an agricultural industry group that supports the legislation. Bill opponents said it could prompt some people to bring even more feral hogs into Oklahoma to be shot by hunters. The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service said damage caused by feral swine across the United States could top $2 billion. “If you are a farmer, they can clean out your crops overnight,” Dale Nolte, the inspection service’s program manager, said in an interview. “We have farmers tell us they have given up on planting high-dollar crops because of the feral hog problem.” Texas, Oklahoma and California have the highest numbers of feral swine in the country, Nolte said. The inspection service has operations to remove them in 38 states, Nolte added. “The problem is that feral hogs are so prolific that we have to trap 70 percent of the pig population every year just to maintain the population level we have right now,” said Kevin Grant, Oklahoma Wildlife Services state director for the U.S. Department of Agriculture. “Out in the wild, feral hogs are an ecological nightmare. There is very little that is beneficial to native wildlife that come from feral swine,” Grant said. 