SIR simulator 1.0: A stochastics, individual-based, spatially-explicit simulation model designed to improve management of insect transmitted plant pathogens

Insect transmitted plant pathogens affect crop production worldwide. Because most adult insects fly and many have broad host ranges, insect population dynamics depend on movement of winged adults among habitats which may include crops, natural vegetation, and ornamental plants. While farmers may treat fields with insecticides, fields will be recolonized if in proximity to a vector source habitat. To improve predicting effects of agroecosystem composition on vector population dynamics and, in turn, pathogen spread, a stochastic, individual-based, spatially explicit model was developed. The simulation model was derived from a Susceptible-Infected-Replaced mathematical model. However, insects and plants took only integer values, with spatial location tracked on an x/y coordinate system. Further, plants and insects were subjected to random events such as local and long-distance dispersal. Default simulations assumed an agricultural region with 10,000 plants (100 plants x 100 rows) divided into a treated and untreated area. In default simulations, pathogen spread was prevented only when the vector was lost from the region. For some combinations of vector life history characteristics, imbalances in immigration and emigration between the treated and untreated area contributed to vector loss. Additional simulations evaluated interactions among vector life history characteristics and size and distribution of treated and untreated fields. Results demonstrate that agroecosystem composition has complex, but predictable effects on insect population dynamics and, in turn, pathogen spread. Development of more refined system specific models provides opportunity to optimize control of insect transmitted plant pathogens and could contribute to decision support systems.