Study On The Residue Dynamic And Application Of Difenoconazle In Postharvest Mango

The preservation effect of fungicide difenoconazole in mango on postharvest and the difenoconazole residue dynamics in mango were investigated, and software models were applied in the dietary exposure risk assessment of difenoconazole in mango. This study attempted to evaluate the application and safety of Difenoconazole in mango, and provide scientific basis for its rational use in the process of production and storage. The main research contents and conclusions were as follows:The toxicity of difenoconazole to Colletotrichum gloeosporioides (Penz. Sacc.) and Botryodiplodia theobromae(Pat.) in postharvest mango was determined by mycelium growth rate methods in laboratory. The results showed that difenoconazole had good effects against C. gloeosporioides and B. theobromae. The sensitivity of4strains to fungicide was different. The toxicity EC50value of difenoconazole to C. gloeosporioides (strains MCOland MC02) was0.425and3.917mg/L, and the EC50value of difenoconazole to B. theobromae (strains MD01and MD02) was0.326and2.421mg/L.The results of Antisepsis tests showed that, the preservation effect of mango is bette when difenoconazole was sprayed preharvest,and then mangos were dipped in drug after they were havested. When sprayed with component of1000mg/L and given dipped treatment of effective component of200and300mg/L, the morbidity of mango decreased, the storage time were prolonged, and the flavor and nutritional quality of the fruit were kept well And the results showed that the antisepsis effect was the best with the concentration of200mg/L.An analytical method was developed for the determination of difenoconazole residue in mango by gas chromatography(GC). The recoveries were79.8%to100.7%at three spiked levels(0.05mg/kg,0.5mg/kg and2mg/kg),with the relative standard deviations(RSd)of0.81%～4.39%.The limit of detection(LOD) was0.0025mg/kg. The developed method was rapid, simple, cheap, high efficient and sensitive.The residue degradation behavior of difenoconazole in postharvest mango was studied. The whole fruits were stored at25℃and13℃respetively after treatment with soaking in difenoconazole solution The results showed that the half-life of degradation for difenoconazole was14.11～15.03d in mango when they were stored at25℃; the half-life of degradation for difenoconazole was19.97～20.56d in mango when they were stored at13℃. The residues in peel, full fruit and pulp were at the range of0.0402～0.763mg/kg.The dietary exposure risk assessment results showed that the difenoconazole daily exposure of the2to6years old children is higher than that of the adults by about one order of magnitude. The potential risks of2to6years old girls were higer than that of the boys; and the potential risks of adult male were higher than that of adult women. In general, the residues of difenoconazole in mango in our country showed low food dietary harm to children (2to6years old) and adults consumers, and the potential risk is low.The MRL values of difenoconazole on mango in our country has not been stipulated up to date.After stored for52d, difenoconazole residues on mango were all higher than0.07mg/kg, and mango got rotten to lost its commodity value. To sum up, difenoconazole has a preservative antisepsis effect on postharvest mango, but if reference to the MRL of the international Codex Alimentarius Commission of the0.07mg/kg, difenoconazole residues were on the high side.Therefore, difenoconazole may be more suitable for pretreatment for mango when campared to the post-processing, for it could obtain control effect, and can reduce the drug residues as well.