A single Asian citrus psyllid picked up during routine trapping in Dinuba, Calif., quickly turned into multiple finds as inspectors began looking at neighboring trees.

The infestation involves numerous adult and immature psyllids on residential citrus trees, which have since been treated with insecticide, said Steve Lyle, spokesman for the California Department of Food and Agriculture, Sacramento.

The news of what appears to be a breeding psyllid population was disappointing to Joel Nelsen, president of Exeter-based California Citrus Mutual.

“So the question now becomes, how quickly did we find it and was it quick enough to be able to stop from spreading?” Nelsen said. “We don’t know yet.”

Asian citrus psyllids are a concern to citrus growers because they not only feed on trees, sucking sap and weakening them, but they can also carry citrus greening.

Also known as huanglongbing, or HLB, the disease is caused by a bacterium that can weaken or kill citrus trees. It is harmless to humans.

With approval from homeowners, the state has treated citrus trees within 800 meters of the original finds.

Both state and U.S. Department of Agriculture quarantines are in the works, Lyle said.

State and county inspectors will conduct a delimiting survey, including increased trapping around the infestation, to determine if the pest has spread.

If no further psyllids are found, Nelsen said he expected restrictions to be placed within a 5-mile radius of the infestation, much as they were around a Porterville infestation.

The quarantine includes requiring growers to remove all plant material from citrus loads before they leave the area. Nursery plant movement also is restricted, unless the trees are grown in a USDA-approved structures.

Nelsen said he didn’t know how many commercial citrus operations would be affected.

Porterville, where six psyllids were trapped in July, is about 51 miles southwest of Dinuba.

Some point to Highway 65, which runs through Porterville, as a possible pathway since trucks use it to haul citrus from infested Southern California groves to the San Joaquin Valley.

But Nelsen said no one has theories yet about the origin of the Dinuba infestation.

The infested trees originated from a San Joaquin Valley location, which has been inspected and found free of psyllids, he said.

State officials have begun questioning the homeowners about their travels and work to determine how the pest made its way to Dinuba.

Nelsen said these latest finds also point out the need for the industry to strengthen its message to homeowners about the threats posed by transporting home-grown citrus.

“They (homeowners) have as much at stake as we do,” he says. “Their trees can die just as easily from HLB as commercial trees can. They have to be cognizant of the threat they are posing.”

Although HLB is endemic in Florida and has caused that state’s citrus industry billions of dollars of losses, only one case — in a residential tree in Hacienda Heights near Los Angeles — has been confirmed in California.