Modelling and mapping spread in pest risk analysis: a generic approach

Assessing the likelihood and magnitude of spread is one of the cornerstones of pest risk analysis (PRA), and is usually based on qualitative expert judgment. This paper proposes a suite of simple ecological models to support risk assessors who also wish to estimate the rate and extent of spread, e.g. when modelling the dynamics of invasion and the economic impacts that may result. Models are based on simple ecological principles, such as logistic growth, radial range expansion and population growth in combination with dispersal. Different models capture different perspectives of the spread process, being based on pest density or simply presence/absence, and they compare spatially explicit and spatially implicit approaches. A case study on Diabrotica virgifera virgifera is provided for illustration. The suite of models requires further development and testing with the risk assessment community building familiarity before their more general application in PRA.