Fig. 4.

SECIR simulation model comparison. Scenario-based simulations integrating disease control strategies of HLB via canine, PCR, and visual survey to detect CLas infections over a 10-y period in a 16.2-ha (40-acre) orchard with 10 initial edge infections. Fiscal outcomes are based on actual orchard management costs for 180-d survey intervals and removal of infected trees postdetection (SI Appendix, Figs. S19–S22 shows full 10-y simulations). (A) Five- and (B) 10-y grove snapshots from a single simulation run where the hosts are color coded (susceptible [S; green], exposed [E; blue], cryptic [C; orange], infected [I; red], and removed [R; black]) dots indicating the spatial location and individual tree disease status within each of six contiguous citrus planting blocks. Cryptic denotes infectious CLas individuals that are asymptomatic, while infected denotes CLas hosts that are both infectious and showing symptoms. (C) Disease dynamics and resulting tree numbers for SECIR partition for each detection method when integrated into control over 10 y. (D) Predicted dynamics of operating profit per acre for additional scenarios involving initial introduction settings (edge or random) and removal protocols (within 30 d or delayed removal up to 90 d postdetection). Profits decline steadily when deploying PCR or visual detection methods, leading to losses early in all scenarios. PCR detection is infeasible throughout due to the high cost of assays, whereas canine detection sustains both viable plantings and long-term profits when deployed twice a year, particularly when paired with prompt removal (SI Appendix, Figs. S23 and S24 shows additional removal delay and replanting effects when deploying canines).