Assessing pesticide effects on non-target invertebrates using long-term monitoring and time-series modelling.
One way of assessing ecotoxicological effects of pesticides at the farm level is by long-term environmental monitoring coupled with time-series modelling. This is illustrated with 20 years of data on the density of sawflies (Symphyta: Hymenoptera) in cereals on a 62-km2 area of West Sussex. The summer use of aphicides in the area first became important in 1989, when 7km2 were treated with dimethoate. Based on pre-1989 data, annual sawfly densities were found to be related, with a l-year lag, to the proportion of cereal fields which were undersown and to summer rainfall and temperature, with a strong autoregressive component. In 1989, sawfly density in the area treated with dimethoate was less than one-tenth of that predicted by the model.