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 c abbage root By eggs (Delia radieum L.) exposed on the soil surface around t he plant stein and the mean density of eggs per plant. The Kono-Sugino's mo del was fitted to a total of 125 population estimates, each based on 10 pla nt samples collected from cauliflower fields in 1994 and 1995 (P = 0.001: R -2 = 0.64). When the model was compared with an independent data set consis ting of 39 population estimates collected in 1995, an analysis of covarianc e showed no significant differences between the regression lines. The effic iency of the binomial method was compared with absolute sampling in terms o f relative precision and cost efficiency. The binomial method had a high co efficient of variation, RV approximate to 0.85, due to large biological err or. In spite of this, binomial sampling was more cost efficient than the ap plied soil sampling when between 10 and 30 plants were examined for the pre sence of visible eggs.