A Spatial, Markovian Model of Rangeland Grasshopper (Orthoptera: Acrididae) Population Dynamics: Do Long-Term Benefits Justify Suppression of Infestations?

Using 49 yr of rangeland grasshopper (Orthoptera: Acrididae) survey data for Wyoming digitized into a spatially explicit format, we constructed a two-state (infested or uninfested) Markov chain model to evaluate the probabilities of population changes between states at the scale of 1 km2. Our analyses revealed that only very limited areas of Wyoming are likely to support multiyear infestations of rangeland grasshoppers. Across the state, 91% of the land has a >50% probability of a transition from infested to uninfested conditions from one year to the next. Considering only the land that has ever been infested by grasshoppers, 55% of this area was found to have a >90% probability of becoming uninfested in the year after an infestation. The life expectancy of a grasshopper infestation in Wyoming is generally