Residual Dynamics of Imidacloprid on Shed Strawberry

The HPLC method was carried out for determination of the final residue amount and dynamic degradation of 10% imidacloprid WP in strawberry fruit.The lowest detection limit of instrument for imidacloprid was 0.14 ng,and the limit of quantification in strawberry fruit was 2.8 μg·kg-1.The average recovery was 81.6%～97.21%,and the standard deviation was 2.76%～6.41%.The results showed that the degradation equations of imidacloprid accorded with the first-order kinetics equation in different planting conditions.They were as C=0.442 9e-0.135t(r=-0.981 8),C=1.622 5e-0.153 2t(r=-0.987 7),C=0.670 5e-0.121 7t(r=-0.969 4) and C=1.814e-0.152 7t(r=-0.992 0),with the degradation half life of imidacloprid in strawberry was 4～6 d.And much of imidacloprid residues were on the surface of the fruits.Strawberry treated 3 times with two concentrations of imidacloprid and 14 days after the last application,the residues in strawberry were below 0.2 mg·kg-1.