The California Department of Food and Agriculture has expanded the Asian citrus psyllid quarantine around the city of Porterville after traps picked up a single insect west of the city.
The quarantined area in Tulare County now encompasses 746 square miles, according to a news release.
The new area can be viewed on maps on the CDFA website.
In addition to quarantines in parts of Tulare, Fresno and Kern counties, the state has Asian citrus psyllid quarantines in Imperial, Los Angeles, Orange, Riverside, San Bernardino, San Diego, Santa Barbara and Ventura counties.
The quarantines restrict plant movement. Commercial citrus can be moved within the areas or out of the areas if growers first remove stems and leaves.
An alternative is to treat the grove with an approved insecticide just prior to harvest to ensure the pest doesn't hitchhike out of the area on the fruit.
The Asian citrus psyllid is a "grave concern" to the California citrus industry because it can transmit citrus greening, although known as huanglongbing or HLB.
The bacterial disease is harmless to humans and other animals, but it can weaken and even kill to citrus trees.
In Florida where citrus greening is entrenched, it has caused more than $3.6 billion in economic losses, according to a University of Florida report.