Weiqi Luo, PhD (he/him/his)
Principal Research Scholar
North Carolina State University
Fort Pierce, Florida, United States
Tim Gottwald
USDA
Fort Pierce, Florida, United States
Drew Posny
USDA
Fort Pierce, Florida, United States
Neil McRoberts
UC Davis
Davis, California, United States
Leigh Sitler
North Carolina State University
Fort Pierce, Florida, United States
Kevin Duan
North Carolina State University
Tempa, Florida, United States
Clive Bock, PhD
Research Plant Pathologist
USDA-ARS
Ft. Pierce, Florida, United States
Huanglongbing (HLB), caused by C. Liberibacter asiaticus (CLas), is spread by the Asian citrus psyllid (ACP), and is the greatest threat to California’s citrus industry. First detected in Los Angeles in 2012, HLB has since spread through residential areas in Southern California. To improve surveillance and response efforts, a risk-based survey (RBS) model was developed, designed to adapt annually as HLB dynamics change. The spread of HLB is influenced by both natural and human-mediated factors. Natural factors include ACP establishment and confirmed HLB-infected citrus locations, while human activities—such as travel from HLB-infected citrus regions, movement of citrus materials, nurseries, packinghouses, farmers' markets, and proximity to restricted lands—also play a role. Human-related factors account for about 26.3% (18.4–38.4%) of HLB spread across different years, while natural factors explain the remaining 73.7% (61.6–81.7%). Global mobility played a key role in early HLB detections in new areas, whereas ACP density became the primary driver of disease spread once HLB was established. A retrospective analysis from 2015 to 2022 assessed the performance of the RBS model, showing a predictive accuracy of 88% to 97%. These findings confirm the model’s reliability for guiding early detection strategies for surveillance activities and targeted interventions to help manage HLB in California.