Residual Degradation Dynamics And Residue Of Deltamethrin In Yali Pear Fruit

With China joining into WTO,fruit export became large, Occident set "green barrier" on our produce, and were more and more strict with our export fruit. Therefore ,the residul in fruit became one of the most important factor which affect the export of fruit. So it was necessity to developed "non-public hazards " pear vigerously ,to improve the edible safety and market competence ability, to achieve "non-public hazards " pear production and consuption.Pear was one of the world five fruit ,also was traditional preponderant fruit trees in our country.The culture area and the yield of pear in our country are both took the first place in the world. But as the most major pest of pear tree, Psylla chinensis Yang et Li, pear yellow phylloxerid and Grapholitha molesta Busck were distributing abroadly in the pear producing area in our country,made bad effection to the pear producing quality and quantity. At the present time ,pyrelhroid pesticide was more and more used to prevent and cure the pear pest. And as one of pyrelhroid pesticide , deltamethrin had good effection to pear pest.,also commenly used in pear produce area in our country.There was few report on the study of residual and distributeing analysis of deltamethrin in yali pear .Hence , deltamethrin as the study object, was sprayed in order to proceed the study of residual degradation dynamics , distributeing and the relationship between the different effect factor and the final residue. Residue was detected by GC.The main results were as follows:1 Studies on residual degradation dynamics of 2.5% deltamethrin in Yali pear fruit, sprayed in three different period as the last ten days of April, the the last ten days of May and the middle of August , were according to spraying once.sampling time after time. The results showed that: Degradation curve equations of deltamethrin in the three period were C=0.3201e^-0.0808t C=0.2226e^-0.0862t, C= 0.3092e^-0.0983t respectively, the correlation coefficients were : 0.9690, 0.9131, 0.9865 respectively, and the half lives were 8. 58d, 8. 04d, 7.05d respectively. Residual degradation dynamics of these three period all accorded with C=C0e^-kt, and all had high relativity , and in normal conditions , degradations were very fast.2 The residual degradation dynamics of 2.5% deltamethrin in Yali pear pericarp, sprayed in the the last ten days of May and the middle of August, were C=1.0435e^-0.0577t C= 0.9300e^-0.0868t respectively, the correlation coefficients were 0.9901 and 0.9917 respectively . Residual degradation dynamics of these three period all accorded with C=C0e^-kt , and all had high relativity .The residue of deltamethrin in Yali pear flesh increase first .decreased later, had the higest residue at the first day after sprayed .3 The residue of deltamethrin in whole Yali pear fruit mostly distributed in pericarp, only few residue permeated in flesh, non-residue in core . The residue of deltamethrin in Yali pear fruit was obviously contactile residue.4 The residue of 2.5% deltamethrin in Yali pear fruit, diluted 2000 times and sparyed once and three times , were 0.020mg/kg> 0.031mg/kg relativity . The result showed that : the final residue in Yali pear fruit was influenced by different spraying times of deltamethrin . But whatever sparyed once or three times, the final residue in Yali pear fruit was not higher than MRL.5 The final residue of deltamethrin in the non-bagged Yali pear was 0.020mg/kg⁰.031mg/kg. The residue of the bagged was lower than the LOD. The result showed that it can reduce the final residue of phoxim in Yali pear fruit by bagging when fruit growth .