Aim: The aim of this study is to determine whether changes to the seasonal and circadian timing of propagule release can a have a significant effect on the area covered by resulting aerial dispersal.

Methods: Using the atmospheric pollution model (TAPM), an existing meso-scale dispersal model, a range of release patterns was simulated and the resulting deposition compared. Comparisons were based on observations of deposition patterns and the calculated area of deposition.

Main conclusions: Simulations performed in this study show that, for small propagules, changes to the timing of release can lead to alternate, clearly differentiable dispersal events. Small changes in both the seasonal and circadian patterns of release can have significant effects on the area that experiences deposition during the resulting dispersal event. This effect is particularly important at the landscape scale and when there is a need to quantify individual dispersal events. Predictive modelling of aerial dispersal needs to be undertaken with an understanding of the manner in which biological and environmental factors that affect the timing of propagule release can influence results. Results presented highlight the need to characterize the epidemiology of pathogenic organisms of importance to biosecurity as much as possible before they arrive.