Modelling the population dynamics of an arable weed and its effects upon crop yield.
Agrostemma githago and spring wheat cv. Sicco were sown in monocultures and 1:1 mixtures at overall densities of 16, 40, 120, 400 and 1200 plants/m2 in 1981. Data on survival and reproductive performance were used to calculate expected yields at any plant combination and density, and to predict seasonal changes in the density of A. githago. In the absence of control measures and with an initial weed density of 1 plant/ha, A. githago infestation could be expected to cause appreciable yield loss after 6 years. Partial weed control was predicted to have little effect on weed density. >50% seed removal must be effected annually in order to reduce the increase in weed density, and the density at equilibrium. >90% control results in eradication of A. githago, which explains its recent decline in British cereal crops.