Modelling the population dynamics of Papaver rhoeas under various weed management systems in a Mediterranean climate

The demography of the annual dicotyledonous weed Papaver rhoeas and the efficacy of different management practices were studied during three consecutive years in winter cereals in the north-east of Spain. These data were used to estimate the parameters of a weed life cycle model that was used to describe the population dynamics of this species and to predict the effect of various control strategies and integrated weed management (IWM) scenarios. Without control, the annual rate of increase was 40 (lambda(t)), and the minimum control level required to maintain the population stable was 99% of the emerged plants. The annual application of post-emergence and/or pre-emergence herbicides did not prevent the growth of the population. Using various cultural control tactics (delayed seeding, harrowing and fallow) resulted in different trends in the overall population depending on the techniques and combinations analysed. Simulations showed that delayed seeding, fallow and pre-emergence herbicides are the best techniques to employ in IWM programmes, always using a combination of these and other more common practices (i.e. post-emergence herbicides). Sensitivity analysis indicated interaction between the parameters and that the model was especially sensitive to seed losses and also to fecundity, seedling survivorship and emergence. The study shows that new strategies should be sought to control these parameters. To develop IWM programmes for P. rhoeas, the combination of two or more control strategies is required.