SAN FRANCISCO -- Utah and Louisiana joined a growing list of states banning the importation of oak saplings from California nurseries over fears of Sudden Oak Death disease.

"Any nursery that is scheduled to receive a shipment of California nursery stock should reject that shipment and have it returned to California," Louisiana Agriculture Commissioner Bob Odom said Wednesday.

Louisiana is at least the sixth state to refuse stock from California since the fungus, which has killed tens of thousands of oaks in forests there, was found at the nurseries.

Hours after Louisiana made its announcement, Utah agricultural officials issued a quarantine on certain plants and material suspected of carrying sudden oak death disease.

The fungus produces cankers on tree limbs and trunks and leads to death. If introduced in the state, the state Department of Agriculture and Food said it would threaten Utah's $60 million nursery industry.

"We consider sudden oak death disease a serious threat to our nursery industry, and are taking every precaution possible to protect our growers," said Utah Agriculture and Food Commissioner Cary G. Peterson.

West Virginia, Florida, Georgia and Alabama also imposed quarantines, though Georgia has since limited its ban to 28 species rather than all plants. Oaks are far from the only species the fungus can infect. Others include camellias, viburnums, rhododendrums, azaleas and maples.

"This disease poses a potentially serious threat to our $155 million commercial nursery industry as well as our forested lands," Odom said. "This quarantine will remain in place until Louisiana determines that relevant California stock has been declared free from Sudden Oak Death disease."

The fungus is related to the type of organism believed to have caused the Irish potato famine in the mid-19th century. It was found on camellia and viburnum plants at two California nurseries that send plants nationwide.

Louisiana is inspecting and testing plants that came from California before the diseased plants were found at the California nurseries, Odom said.

The fungus causes cankers on trees and can kill within two to three years. So far, it has been found only in the wild in California, where it first appeared, and in Oregon.