The California Department of Food and Agriculture has implemented a new 113-square-mile quarantine around the city of Bakersfield after an Asian citrus psyllid was detected in the south part of town.
The area is in addition to previous quarantines in Kern County.
So far, the state has quarantined parts of Kern, Fresno, San Luis Obispo and Tulare counties.
In addition, it has quarantined Imperial, Los Angeles, Orange, Riverside, San Bernardino, San Diego, Santa Barbara and Ventura counties in their entirety.
The concern is the Asian citrus psyllid may carry the citrus greening or huanglongbing bacteria.
Although harmless to humans and other animals, the disease can weak and even kill citrus trees.
In Florida, where the disease is endemic, it has reduced citrus production by nearly 50 percent and cost the industry more than $4 billion, according to University of Florida figures.
Only one infected tree has been found in California, and that was in 2012 on a residential property in Hacienda Heights, Los Angeles County.
The tree has since been destroyed.
Citrus greening also has been confirmed in Georgia, Louisiana, South Carolina and Texas.