THE EFFECT OF IMPULSIVE SPRAYING PESTICIDE ON STAGE-STRUCTURED POPULATION MODELS WITH BIRTH PULSE

摘要

In most models of population dynamics, increases in population due to birth are assumed to be time dependent, but many species reproduce only a single period of the year. In this paper, we construct a stage-structured pest model with birth pulse and periodic spraying pesticide at fixed time in each birth period by using impulsive differential equation. Using the discrete dynamical system determined by the stroboscopic map, we obtain an exact periodic solution of systems which are with Ricker function or Beverton-Holt function, and obtain the threshold conditions for their stability. Further, we show that the time of spraying pesticide has a strong impact on the number of the mature pest population. Our results imply that the best time of spraying pesticide is at the end of the season, that is before and near the time of birth. Finally, by numerical simulations we find that the dynamical behaviors of the stage-structured population models with birth pulse and impulsive spraying pesticide are very complex, including period-doubling cascade, period-halving cascade, chaotic bands with periodic windows and "period-adding" phenomena.