Geospatial Risk-Based Survey Model for 'Candidatus Liberibacter asiaticus' Detection in Residential Citrus...

Area of Science:

• Plant Pathology
• Entomology
• Epidemiology

Background:

• Citrus huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas) and vectored by the Asian citrus psyllid (ACP), is a severe threat to California's citrus industry.
• HLB was first detected in Los Angeles in 2012 and has since spread throughout Southern California, necessitating enhanced surveillance and intervention strategies.

Purpose of the Study:

• To develop and validate a risk-based survey (RBS) model for improved HLB surveillance and targeted interventions in California.
• To assess the influence of natural and human-mediated factors on HLB spread and to evaluate the predictive performance of the RBS model.

Main Methods:

• Development of a risk-based survey (RBS) model incorporating natural factors (ACP establishment, HLB locations) and human-mediated factors (global mobility, citrus trade, proximity to inaccessible lands).
• Retrospective analysis from 2015 to 2022 to evaluate the RBS model's predictive performance and accuracy.
• Statistical analysis to differentiate the contributions of natural versus human-mediated risk factors to HLB incidence.

Main Results:

• Human-mediated risk factors contributed approximately 26.3% to HLB incidence, while natural causes explained the majority (73.7%).
• Global mobility was critical for early detection in new areas, whereas ACP density correlated strongly with disease spread post-establishment.
• The RBS model demonstrated high predictive power, ranging from 88% to 97% between 2015 and 2022.

Conclusions:

• The validated RBS model is a reliable tool for developing targeted interventions and early detection strategies for HLB in California.
• Understanding the interplay between natural and human-driven factors is crucial for effective HLB management and safeguarding the citrus industry.