A plant disease with the potential to do far more devastating damage to Florida's citrus industry than canker has spread to Palm Beach and Martin counties, a state agriculture official said Tuesday.

Two citrus industry leaders called on federal and state officials to take immediate action.

A state Division of Plant Industry laboratory in Gainesville confirmed that the residential trees — found in West Palm Beach, Delray Beach, Boca Raton, Hobe Sound and northwest Martin County near the St. Lucie County line — have been infected with citrus greening, said Mark Fagan, spokesman for the state Agriculture Department.

"If there is greening in Palm Beach County, the (U.S. Department of Agriculture) will have to take rapid and severe action," said Nat Roberts, general manager of the Callery-Judge Grove near Loxahatchee and chairman of the Indian River Citrus League.

Greening, also known as yellow dragon disease, causes trees to produce misshapen, inedible fruit and cuts tree yields to almost nothing. The disease, spread by an exotic insect called the citrus psyllid, was discovered in Miami-Dade County on Aug. 23.

The two finds in Homestead marked the first appearance of the disease in the United States.

Since then, greening has been confirmed on 161 trees on 140 properties in Miami-Dade and Broward counties, Fagan said.

Doug Bournique, executive vice president of the Indian River Citrus League in Vero Beach, echoed Roberts' request for a swift response.

"Obviously, the state and the feds have got to act quickly and decisively before it spreads into the commercial groves," Bournique said, adding that growers don't want to see a repeat of what happened with citrus canker.

Canker, a bacterium that blotches fruit and leaves and weakens trees, was detected in Miami-Dade County in September 1995, and has spread since then. More than 9 million backyard and grove trees will be, or already have been, sacrificed to the state's effort to wipe out canker.

Officials say greening is even worse. Tim Gottwald, a Fort Pierce-based USDA plant pathologist, has said that on a scale of one to 10 — with 10 being the most severe — citrus canker is a 3, and greening is a 10.

Greening has already dealt a blow to the state's $1.75 billion plant nursery industry.

In a memo Sept. 14, the director of the Division of Plant Industry, Richard Gaskalla, imposed a quarantine on Miami-Dade County, prohibiting the more than 1,000 nurseries there from moving out of the county all plants that can host the disease or its carrier.

All other Florida counties also were prohibited from shipping possible host plants to citrus-producing states — Arizona, California, Louisiana and Texas, as well as the commonwealth of Puerto Rico. Among the prohibited plants are such popular varieties as orange jasmine and box thorn.

The citrus psyllid was first spotted in Delray Beach in June 1998. Since then the state has been looking for the disease, but a panel of scientists recently assembled to tackle the problem has not determined how to deal with it, Fagan said.

"We are in phase one: detection," Fagan said. "We need to find out how far it has spread. Then we will do phase two: What is the course of action?

"You can use pesticides to get rid of the psyllid, but you can't go into people's back yards and spray pesticides," he said.

Greening affects the plants' vascular systems. Infected trees die in a few years.

Roberts said state entomologist Susan Halbert visited his grove last week looking for pummelo trees, a relative of the grapefruit, to test for greening.

"We believe our samples are still in the lab waiting to be tested," he said. "She said our trees looked fine."

Samples from the finds in Palm Beach and Martin counties are awaiting a second round of tests at the USDA laboratory in Beltsville, Md., he said. That's the procedure with greening, which can't be diagnosed visually.

The disease probably arrived in Florida from infected Asian plant material that came into contact with the psyllids, state agriculture officials have said. Greening "seriously affects citrus in India, Asia, Southeast Asia, the Arabian Peninsula and Africa," according to a state news release.

The state has conducted greening-detection surveys for many years, and stepped up efforts after the psyllid was found, officials said. They also said eradication of the disease is possible because it has been detected early on.

"There are ways to manage it if you manage the insect and remove the infected trees," Denise Feiber, a state agriculture department spokeswoman, said last month.