Reduction of the Toxicity of Fenitrothion to Prawns by Piperonyl Butoxide

The effectiveness of piperonyl butoxide (PB) in reducing the mortality of striped prawn and kuruma prawn during exposure to fenitrothion (FS) was examined. The 24-h LC₅₀ values of PB for striped and kuruma prawns were 3.5 and 1.6 ppm at 25°C, respectively. Therefore, PB-treatment for both prawns was conducted at 0.25 ppm, corresponding to one-tenth of the mean of both 24-h LC₅₀ values. The PB-pretreatment before FS-exposure and also the addition of PB to FS-water were effective in decreasing the FS-toxicity to both prawns. The most effective reduction of the toxicity to the prawns was obtained by continuous PB-treatment before and during FS-exposure, resulting in extensions of 50% survival time by 4–6 times in striped prawn and 10–16 times in kuruma prawn, compared with the respective control groups non-treated with PB.