Asian citrus psyllids on a citrus leaf. Courtesy County News Center

A quiet, but formidable, opponent is threatening San Diego County’s landscape, and if successful, could make our region’s backyard and commercial citrus simply disappear. Public awareness and community collaboration is the key to avoiding this demise.

The first San Diego County detection of a deadly plant disease — Huanglongbing, also known as HLB or citrus greening — was announced this month by county, state and federal officials, and a quarantine zone has been established in North County around the Oceanside detections. While not harmful to humans or animals, the disease kills citrus trees, and there is no cure.

HLB, which has previously been detected in more than 2,400 trees in Los Angeles, Orange, Riverside and San Bernardino counties, is spread by a tiny pest called the Asian citrus psyllid as it feeds from tree to tree. No bigger than a grain of rice, the pest doesn’t appear threatening, but the disease it can carry is deadly for citrus and has decimated Florida’s commercial citrus production.

While the presence of the psyllid is not new — the first psyllid detected in California was found here in San Diego County in 2008 — in late 2020 officials detected the first in the county carrying the bacterium that causes Huanglongbing in Fallbrook. Until then, local residents and citrus growers had been successful in keeping the plant disease at bay.

This detection brings with it a renewed sense of urgency and strong need for continued collaboration between residents, industry and government. Only if we work together, can we give San Diego citrus its best chance at surviving this potentially devastating disease.

The most effective way to limit the further spread of the disease in San Diego County is to control the spread of the Asian citrus psyllid. The local citrus industry and agricultural officials are working aggressively to limit populations of this dangerous pest.

The United States Department of Agriculture; California Department of Food and Agriculture; San Diego County Department of Agriculture, Weights and Measures; San Diego County Farm Bureau; San Diego County Citrus Pest Control District and others are coordinating a number of activities to identify and reduce psyllid populations and detect any additional infected trees.

Activities include active monitoring of bug traps for psyllids, testing of plant material for the disease, removal of infected trees, releases of natural enemies as a biocontrol agent, communication and coordination among local growers and enforcement of the newly established quarantine zone requirements.

While agricultural officials and the citrus industry are putting measures in place, the ultimate solution lies with residents. We need residents to help keep their trees healthy and cooperate with agricultural officials who are working to save their backyard citrus.

How San Diego County Residents Can Help

  • Report any signs or symptoms of Huanglongbing to the free Pest Hotline at 800-491-1899. The symptoms include blotchy yellowing of leaves, yellow shoots, lopsided, small and rancid-tasting fruit, and premature, excessive fruit drop. 
  • Allow agricultural officials to access your property so they can look for symptoms and treat for the pest.
  • Take proper care of your tree. Obtain citrus care advice from CaliforniaCitrusThreat.org.
  • As part of your tree maintenance, visit your local nursery or garden center to get advice on products that can help protect your citrus tree.
  • When pruning your tree, dry out citrus clippings or double bag them before removing the plant material from the property.
  • Obey quarantine requirements by not moving citrus plants, foliage, or fruit in or out of your area, or across state or international borders.
  • Consider removing unwanted or uncared for citrus trees so they do not become a host to the pest or disease.

The presence of Huanglongbing in our county does not signal a lost cause. Citrus is a beloved part of our landscape — from the groves dotting North County hillsides to the nutritious fruit grown in backyards across our region – and we must all do our part to protect our citrus.

Ha Dang serves as the Agricultural Commissioner and Sealer of Weights and Measure for San Diego County. Hannah Gbeh is the Executive Director of the San Diego County Farm Bureau. Enrico Ferro is the General Manager of the San Diego County Citrus Pest Control District and a licensed pest control adviser.

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