Methods of analysing data to compare effects on populations of carrot fly (Psila rosae) larvae on carrots of treatments with exponentially-increasing doses of granular insecticide formulations

Effects of insecticide treatments were assessed by comparing the percentages of undamaged carrot roots on insecticide-treated and untreated check plots. A dose-response relationship based on a log-log transformation was derived and illustrated with data for six insecticides from two field experiments. Formulae are provided for estimating doses corresponding to given levels of decrease in the numbers of carrot fly larvae. Guidance is given on sample sizes needed and constraints on the accuracy of the estimates are stated. Examples are given of the use of the dose-response relationship to compare insecticide treatments within and between experiments.