Binomial sampling as a cost efficient sampling method for pest management of cabbage root fly (Dipt., Anthomyiidae) in cauliflower

A binomial (presence–absence) sampling plan has been developed based on the relationship between the proportion of cauliflower plants having visible cabbage root fly eggs ( Delia radicum L.) exposed on the soil surface around the plant stem and the mean density of eggs per plant. The Kono–Sugino's model was fitted to a total of 125 population estimates, each based on 10 plant samples collected from cauliflower fields in 1994 and 1995 (P=0.001; R²=0.64). When the model was compared with an independent data set consisting of 39 population estimates collected in 1995, an analysis of covariance showed no significant differences between the regression lines. The efficiency of the binomial method was compared with absolute sampling in terms of relative precision and cost efficiency. The binomial method had a high coefficient of variation, RV ≈ 0.85, due to large biological error. In spite of this, binomial sampling was more cost efficient than the applied soil sampling when between 10 and 30 plants were examined for the presence of visible eggs.