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PRE-HLB travels to California

By hlb-editor | March 29, 2023 | Event and News, News | 0 comments


From PRE-HLB and the Plant Health Service of the Generalitat Valenciana we would like to thank all the staff of the official agencies of California and USA, USDA and CDFA and the University of California, especially Dr. Neil McRoberts, from the University of Davis, for the interest shown in sharing and disseminating their experience in the management of the HLB disease and the associated vector. We are grateful for the extensive agenda they organized for us, which allowed us to learn in depth about key aspects of pest management, from the plant certification program, official controls, to the biological control program of the psyllid. The collaboration between the different public agencies, private companies, associations, liaison agents, the affected agricultural sector, etc., makes the success of the containment program possible. This system should serve as an example to carry out a good control plan against any pest, especially in the event of the hypothetical entry of this serious disease into the EU.


Within the project a technical visit was made by the staff of the Plant Health Service of the Conselleria de Agricultura, Rural Development, Climate Emergency and Ecological Transition and the Instituto Valenciano de Investigación Agrícola (IVIA) to the state of California in order to learn about the technical and operational aspects of HLB pest management and the technical and operational aspects of the management of the HLB pest and its insect vector, as well as their Rural Development, Climate Emergency and Ecological Transition.

The following visits were made:


University of Davis (UC Davis) – Plant Pathology Department. Dr. Neil McRoberts and his team showed the risk-based prospecting model and the different citrus genomics studies being carried out in the department. They explained that the program has the figure of the “Grower liaisons” who is the contact person in each county to act as a link between the growers and the official agencies (the CDFA). They play a fundamental role in the communication and understanding of the program measures established by the CDFA. Dr. Kris Godfrey, from the Contained Research Facility at UC Davis, showed us the research they are doing in the biosecurity lab.

(Photos: Dr. Kris Godfrey and Dr. Neil McRoberts at the facility. HLB symptoms on leaves)


CDFA: California Department of Food and Agriculture. Citrus Pest and Disease Prevention Division (CPDPD) in Sacramento. Victoria Hornbaker, Director of CPDPD, explained the management carried out after the detection of the first positive and the current distribution of the Diaphorina citri psyllid (ACP) in the counties of California and the quarantine areas established in Los Angeles, Orange, Riverside, San Bernardino, and San Diego’s counties with confirmed presence of HLB and positive ACP. They also detailed the management program being carried out in each of the 3 districts into which the county of California has been divided, North District, Central District (Visalia and Fresno) and South District (area with confirmed presence of HLB and ACP), as well as the mandatory phytosanitary treatments being carried out in the demarcated area and other treatments in private homes that collaborate on a voluntary basis. The CDFA has designed a risk-based disease spread prediction model (HLB Risk Survey).They were able to visit the CDFA Diagnostic Laboratory located in Sacramento. The diagnostic center is divided into 5 specific laboratories: Botany, Plant Pathology, Entomology, Seeds, and Nematodes.

(Photos: Entomology laboratory: PCA information table and PCA captures)


Citrus conference at the Visalia Convention Center organized by the Citrus Research Board (CRB). The citrus conference is held annually to discuss the opportunities and challenges of the citrus industry in California. Several presentations were given by experts and researchers on new varieties, resistant rootstock studies, integrated pest management, mechanization for phytosanitary application, water uses, etc. In addition, there was an exhibition with different posters of studies and research.

(Photos: Poster and program of the “Citrus conference”)


Limoneira Company Office (Ventura). Meeting at the office of the Limoneira Company, a company dedicated to the production, packing and marketing of citrus, where they were told that the industry has had to adapt to the new situation, especially in the mandatory measures of protection through appropriate mesh for the movement of fruit between different counties. Participants included grower liaisons from the area, CDFA citrus division supervisor Keith Okasaki, professors from the University of California, grower representatives, industry representatives…. The CDFA supervisor detailed the framework for the quarantine zones established for HLB and/or ACP: they have specific regulations for the movement of fresh fruit between the 6 quarantine zones and requirements for nurseries.

(Photos: Transport of fresh fruit in netted trucks and maps of quarantine zones established for movement of fruit and plant material between nurseries)

They were also able to see a demonstration of a private company “Canine Detection Services” for the detection of ACP with trained dogs, as well as a citrus plantation where we could see Diaphorina citri.

(Photos: Demonstration of the search for the psyllid with a trained dog and Diaphorina citri in lemon trees)


University of Riverside. Citrus Clonal Protection Program (CCPP). Dr. Georgios Vidalakis and his collaborator Paulina explained the clonal program and the procedure for the introduction and sanitation of new varieties. They were able to see a demonstration of the cleaning of rods for both rootstocks and varieties.

(Photos: Explanation by Dr. Vidalakis on the Plant Material Sanitation Program and informative poster)

University of Riverside (UCR) entomology facilities. Meeting with Dr. Mark Hoodle (UCR), David Morgan (CDFA) and other colleagues explain how they introduced the original colony of Tamarixia radiata from Pakistan and the breeding and release system they use. They showed the Tamarixia radita breeding facilities.

(Photos: Tamarixia radiata breeding facilities at UC Riverside)


Visit with the CDFA survey team to a private home located within the HLB and ACP demarcated area in Ventura County. They showed how the survey protocol is applied within this zone and were able to see how they perform a visual inspection and take samples of leaves and roots. They also explained that they do not always have the cooperation of the citizens and sometimes this complicates the control work.

(Photos: Citrus sampling equipment in a private garden in a demarcated area in Los Angeles)


Wonderful Citrus Nursery (Visalia). Jose Lima. Nursery director. The director explained the production system of nursery plants according to the clonal production program of the University of Riverside. The design of the facilities and the prophylactic measures for personnel ensure protection against psyllid entry and contamination of plant material. The nursery voluntarily participates in an official sampling program by CDFA inspectors that ensures the health of plant material is free of HLB.

(Photos: Signs with biosecurity measures at Wonderful Citrus Nursery’s facilities)


TreeSource AC Fruits (Woodlake). Joshua Thompson. General Manager. PRE-HLB was able to visit another production nursery that sources sanitized material from CCPP and able to visit the facilities where they carry out the entire production process from seed planting, grafting and preparation for marketing.

(Photos: Production of potted plants and propagation of rootstocks by cuttings at TreeSource AC Fruits)


Citrus Lindcove Foundation Block (Exeter) – Ashraf El-Kereamy. Director of Lindcove Research and Extension Center (LREC). This center belongs to the University of California and its function is to research and extend the results directly to growers. The facilities consist of research plots, citrus quality, root and entomology laboratories, demonstration facilities, dissemination of results and education. They also organize demonstration fairs, tastings, and workshops for children.

(Photos: Presentation of the different experience programs at the Citrus Lindcove Foundation Block)


This concludes the visit agenda of the technical trip to California in which Pre-HLB had the opportunity to learn and document about the management of the disease and its associated vector. The project would like to highlight and thank the participation of all the professionals who assisted and showed their knowledge.


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