Canary palms in rural areas as invasion bridges: Exploring simulated red palm weevil spread across date palm plantations

The red palm weevil, Rhynchophorus ferrugineus, (RPW) is an invasive pest that causes significant damage to date palms (Phoenix dactylifera L.) in agricultural plantations and to Canary palms (P. canariensis) in residential areas. Canary palms provide a higher-quality habitat for RPW than date palms. However, little is known about how RPW spreads between these palm species —whether it disperses randomly or host oriented. To explore how variation in Canary palm density affects RPW spread, we developed a coupled map lattice simulation model in artificial landscapes with alternating date palm plantations and villages, represented as patches with varying densities of Canary palms that enhance habitat connectivity between the date plantations. Dispersal between cells occurs based on cell scores that account for host abundance, dispersal behavior, and RPW attraction to palm hosts (oriented dispersal). Our results show that RPW spread rates are influenced by both cell scores and Canary palm densities. In landscapes with low Canary palm density, RPW spreads were limited under random dispersal. However, with a low degree of oriented dispersal, spread rates increase sharply with increasing Canary palm densities, and leveling off at the highest densities, suggesting that RPW uses these palms as stepping-stones to reach distant date plantations. At higher degrees of oriented dispersal, spread rates remain stable at low Canary palm densities, then increase linearly at higher densities. The sensitivity analysis highlighted key knowledge gaps on RPW dispersal, emergence patterns from different palm species, and the relative susceptibility of these species to infestation.