Residue and dietary intake risk assessment of difenoconazole in Panax notoginseng

The decline dynamics,absorption,transportation and distribution of difenoconazole in Panax notoginseng were investigated by field trial and GC-ECD.The results showed that the half-life of difenoconazole in P.notoginseng were between 12.3 to 12.8 days.In the case of the foliar spray,difenoconazole could be absorbed directly by P.notoginseng leaves and then transported downward to the root quickly.The terminal residue level was depended on the portion of the plant,with the order of flower>fibrous roots>root.When P.notoginseng was treated with difenoconazole 100 g/kg WG in vegetative period before flowers at recommended dosage of 67.5 g(a.i.)/hm2 for 4 times usage with application frequency of 7 days,the highest residue of difenoconazole at harvest was 0.55 mg/kg in root,0.72 mg/kg in the fibrous roots,and 2.25 mg/kg in the flower,respectively,with the interval of 28 days after the last application.It was lower than the maximum residue limit (20 mg/kg) of difenoconazole in P.notoginseng set by European Union.The dietary risk assessment showed that even though the risk of difenoconazole residue on flower was higher than other portion,it was safe for its low risk quotient(RQ)(0.21%).Based on the result,the foliar spray of difenoconazole 100 g/kg WG in P.notoginseng was safe at 67.5 g(a.i.)/hm2 dosage for three times usage with pre-harvest interval of 28 days.