Population dynamics of the bird cherry‐oat aphid, Rhopalosiphum padi (L.), during the autumn and winter: a modelling approach

Abstract 1 A simulation model was developed to investigate the inter‐relationship of factors influencing the population dynamics of the bird cherry‐oat aphid ( Rhopalosiphum padi (L.)) in barley crops during the autumn and winter . 2 The model incorporated algorithms describing alate immigration, development and survival of adults and nymphs , fecundity and morph determination in newly born nymphs. 3 The model was validated against pest outbreaks in barley fields in south‐east England. 4 It simulated accurately the size of the outbreaks with predictions of peak aphid populations within 20% of the observed in all but one case. Similarly, all but one of the year‐sowing date combination predictions of timing of peak abundance fell within 14 days of the observed. 5 A sensitivity analysis of the model highlighted the relative importance of various population processes in determining simulated aphid population dynamics; decreasing mortality rates of apterous nymphs by as little as 5% over the autumn and winter increased peak densities by as much as 60‐fold, whereas increasing daily temperatures by only 1 °C more than doubled peak aphid abundance. 6 The model identified our understanding of the mechanisms of aphid mortality as a limiting factor in the accurate prediction of R. padi outbreaks in the field.