Modeling the Importation and Local Transmission of Huanglongbing Disease: Bifurcation and Sensitivity Analysis

Abstract

Huanglongbing (HLB), primarily transmitted by the citrus psyllid, is the most devastating citrus disease worldwide. Planting disease-free citrus seedlings is one of the significant intervention strategies for HLB. In this paper, a compartment model is used to investigate the importation and local transmission of the disease. Due to the continuous input of the diseased citrus seedlings from outside, the traditional theoretical analysis methods are insufficient to describe and predict its dynamical behaviors based on the analysis determined by the basic reproductive ratio [Formula: see text]. The criteria for the existence and local stability of disease-free and endemic equilibria are deduced. Then a complete theoretical, bifurcation, and sensitivity analyses are carried out on the simplified system. Based on our study, we have the following interesting findings: (a) the importation of diseased citrus seedlings in orchards plays a vital role in the transmission of HLB, and planting disease-free citrus seedlings will effectively inhibit the spread of the disease; (b) the importation of diseased citrus seedlings can affect the stability of the equilibrium of the full system; (c) the simplified system may exhibit some complex dynamic phenomena, such as saddle-node bifurcation, forward bifurcation, backward bifurcation, and bistability; (d) global sensitivity analysis shows that the mortality and biting rate of citrus psyllids have a greater impact on [Formula: see text] than other parameters. These observations provide theoretical guidance for policymakers to determine the long-term viability of implemented HLB intervention strategies.