The citrus greening disease that devastated groves in other parts of the country has been found in Riverside County for the first time since 2017.

Researchers on Monday, May 6, confirmed the presence of huanglongbing, also known as HLB, on a kumquat tree in the yard of a Riverside house where the disease was also found in 2017, according to Tracy Moehnke, a spokeswoman for the Citrus Pest & Disease Prevention Program. The program is funded by California citrus growers and administered by the California Department of Food and Agriculture.

Although the California Department of Food and Agriculture tested the property — near the 60/91/215 freeway interchange — five times since finding the disease there, local citrus disease experts suspect the tree was infected around that same time.

“It can stay basically hidden in the tree and not express itself for years,” Riverside County Agricultural Commissioner Ruben Arroyo said.

Four properties in Riverside County have tested positive for HLB, all in the same area of the city of Riverside. San Bernardino County had one positive test, in the city of San Bernardino.

Meanwhile, 291 infected properties have been found in Los Angeles County, and 689 properties in Orange County, according to Moehnke.

The disease is transmitted tree-to-tree by the Asian citrus psyllid. The insect does not always carry the disease, but it is the only known vector. The psyllid was first detected in Southern California in 2008, and HLB was found in 2012 in Hacienda Heights.

Since then, Riverside officials say they’ve worked hard to stop the spread of the disease, which leaves citrus trees with mottled leaves and fruit that is misshapen and fails to ripen, remaining green. The fruit also tastes bitter. There is no known treatment for the disease and trees usually die within three to five years.

In Florida, the disease infected at least 80 percent of the citrus trees within a decade, costing $2 billion in economic impact, and close to two-thirds of the citrus jobs were lost.

State officials mandate any infected tree be removed immediately — even if that tree is the parent navel orange, which gave birth to the Inland Empire’s citrus empire and most of the navel oranges alive today. That tree is in Riverside at the corner of Arlington and Magnolia avenues, close enough to the infected area that it could easily become infected.

Vigilance is required to prevent its destruction, said Georgios Vidalakis, a professor and director of the citrus protection program at UC Riverside.

UCR, along with city and state officials, are covering the tree in a permanent structure, removing adjacent trees that could spread the disease and taking other precautions, but the public’s help is needed to stop the psyllid’s spread, Vidalakis said.

“This is a community disease,” he said. “We can try as much as we like to fight this, and our state Department of Agriculture and our growers are (fighting), but if our neighbors, if our community altogether doesn’t do the right thing, we’re going to lose the battle.”

The Citrus Pest & Disease Prevention Program recommends these tips to protect citrus trees.

Inspect trees for the Asian citrus psyllid and Huanglongbing

Don’t move citrus into or out of your area

Buy citrus trees from licensed, local nurseries

Only use registered budwood — the young branches used for grafting

Cooperate with agriculture crews

Apply products that protect your tree

Dry or double bag plant clippings

Vidalakis and Arroyo implore people to avoid moving any citrus — either trees or fruit — out of the area, and to keep an eye out for signs of the disease.

Anything suspicious, they say, should be reported to the state pest hotline: 1-800-491-1899.

More information is available at https://californiacitrusthreat.org.

PROPERTIES WITH HLB

Orange County: 689

Los Angeles County: 291

Riverside County: 4

San Bernardino County: 1

Source: Citrus Pest & Disease Prevention Program