POPULATION-DYNAMICS OF THE WESTERN CORN-ROOTWORM - FORMULATION, VALIDATION, AND ANALYSIS OF A SIMULATION-MODEL

A simulation model of western corn rootworm, Diabrotica virgifera virgifera LeConte, population dynamics was developed. The model includes functions for pre-imaginal development and mortality, and ageing, development, oviposition, mortality, migration, and dispersal of adults. Model validation and sensitivity analyses were conducted. Both the timing and pattern of simulated adult emergence were similar to that observed in field populations. The simulated pattern of adult abundance throughout the season was generally consistent with that observed, as were simulated seasonal patterns of oviposition. Model predictions of egg densities at the end of the season were within one standard error of field estimates each year. In neither year did simulated survival of immature rootworms fall within two standard errors of observed estimates, suggesting that factors contributing to immature mortality were inadequately described in the model. Model output was very sensitive to small changes in the parameters of functions describing temperature-dependent development rates of immature rootworms and corn plants, and a function that describes the distribution of age-specific oviposition. Model output was also sensitive to variation in the planting date of corn and the initial population density of rootworm eggs.