Simulation Model of the Mediterranean Flour Moth (Lepidoptera: Pyralidae) in Danish Flour Mills

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The Mediterranean flour moth, Ephestia kuehniella Zeller, is a severe pest in Danish flour mills and was controlled by the use of methyl bromide until its ban in 1998. As a basis for exploring alternative control options, we developed a distributed-delay simulation model of flour moth population dynamics in the mills. Parameters for the temperature-dependent development of egg, larvae, and pupae and the lifespan and fecundity of female moths were obtained from published data. The model was validated against 3 yr of pheromone trap catches of male moths in a Danish mill. The overall phenology of the flour moth population was well simulated and was found to be determined largely by mill temperature and the seasonality of diapausing larvae. Based on the model it was estimated that the moth realizes only 1–3% of its reproductive potential from one year to the next. Reduced fecundity and juvenile mortality are the most likely regulating mechanisms. Model simulations based on historical weather data suggest that the increased temperature inside the mill drives the regular moth outbreaks, and that if mills were cooled to outdoor temperatures, the moth would become an outbreak pest less frequently.