Revisiting a demographic model of pest infestation in farming

Reliable simulations of pest population dynamics are essential tools for effective pest management. Here we present a demographic model designed to describe overwintering stage-structured population dynamics. In addition to accounting for development, mortality, and fecundity, the model explicitly incorporates diapause, a key physiological process enabling pests to survive winter conditions. We detail the formulation of the mortality rate function based on the development rate and the proportion of individuals dying within each developmental stage. Simulations are performed for the case of Lobesia botrana, a major vineyard pest. Results show, under both constant and fluctuating temperature regimes, the necessity of employing a density-dependent fecundity function to regulate population growth. Under constant temperature conditions, when fecundity depends on total population density, the system dynamics converge to a steady state regardless of the temporal discretization step, though peak values vary. Conversely, if fecundity is a function of adult density only, the model yields periodic oscillations. Under variable temperature regimes, diapause facilitates seasonal population resurgence and mitigates peak pupal and adult densities in the fall.