BACKGROUND: Unintentional residual pesticide in soil derived from preceding crops and the transfer to succeeding crops was considered a critical barrier for Positive List System(PLS). Thus, an uncertain risk is predicted for ethoprophos applied at cultivation of preceding crop(Korean cabbage) to succeeding crop(spinach).
METHOD AND RESULTS: Ethoprophos was treated on soil following the recommended dose and 5 times dose according to the safe use guidelines for Korean cabbage after seeding. On the 4 days after harvesting of preceding crop, spinach was sowed. The initial residual amounts of ethoprophos on soil(7.081-19.493 mg/kg) were degraded to 3.832-7.218 mg/kg until the harvest of Korean cabbage, and then finally degraded to 0.011-0.079 mg/kg after spinach cultivation. The uptake rates of ethoprophos from soil by Korean cabbage were 0.01-0.03% and distributed to root(0.150-0.903 mg/kg) and shoot(0.021-0.151 mg/kg), respectively. The residual amounts of uptake and translocation from preceding crop cultivated soil to spinach edible part were found to be below LOQ.
CONCLUSION: The plant back internal(PBI) for ethoprophos is not recommended during sequential cultivation of leafy vegetables, since the residual amounts of ethoprophos in spinach were less than MRL(0.02 mg/kg).