Short-term forecasting of peak population density of the grain aphid (Sitobion avenae) on wheat

The trends in population density of Sitobion avenae in wheat fields were analysed for a total of 32 sites over the period 1975 to 1983 in eastern England and the Netherlands. The peak population density on each field was positively correlated with the population densities at the end of ear emergence, mid-anthesis and the end of anthesis. It was also positively correlated with the observed rates of increase of the aphids on the crop immediately before these stages. Both parameters were incorporated in multiple regressions to forecast peak population density, and data from a further nine populations monitored in 1984 was used to validate the model. The accuracy of these forecasts, based on two counts on the crop, increased from ear emergence to the end of anthesis, the forecast at mid-anthesis of peak density being much more accurate than any other published method.