Residual Dynamics Of Several Pesticides On Shed Strawberry

With anti-season cultivation area increasing, producers lack the safety and the rational use of pesticides knowledge, which will cause pesticide residues exceeding the permissible standards and affect people's health. Therefore, it is of great significance in ensuring the quality of pesticides, reducing its environmental risks, strengthening pesticide management, and guiding a scientific, rational, and safe use of pesticides.To understand the residue dynamics of chlorolthalonil, iprodione, imidacloprid and acetamiprid on shed strawberry and to use these pesticides effectively and safely, the residue dynamics of the four pesticides were studied in different seasons, different growing conditions, different dosages and different treats of the fruits. The results were as follows:The established Solid-Phase Extraction and the capillary GC (SPE-CGC) method was carried out for determination of the final residue amount and dynamic degradation of 75% chlorolthalonil WP and 50% iprodione WP in shed strawberry fruit. The lowest detection limit for chlorolthalonil was 8.6×10-3ng, and the limit of quantification in strawberry fruit was 0.86μg﹒kg-1.The average recovery of chlorolthalonil was 88.17～99.01%, and the standard deviation was 4.43～6.4%. The average recovery of iprodione was 88.15%～112.96%, and the standard deviation was 0.77%～4.54%. 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 0.14ng, and the limit of quantification in strawberry fruit was 2.8μg·kg-1.The average recovery was 81.6～97.21%, and the standard deviation was 2.76～6.41%. To 5% acetamiprid EC, the established Solid-Phase Extraction and the capillary GC (SPE-CGC) method needs further study. The lowest detection limit for acetamiprid was 50ng, and the limit of quantification in strawberry fruit was 5mg﹒kg-1.The results showed that the degradation dynamic equations of chlorolthalonil, iprodione and imidacloprid were accorded with the first-order kinetics equation in different planting conditions. The degradation half lives of the former three pesticides in strawberry were 4～6d. No acetamiprid residue was detected 1d later. The environmental condition played an important role, the former three pesticides in strawberry fruit degraded more quickly in Summer than in Spring. Most of the residue was on the surface of the fruits and the residue of a double dose was higher than a safe dose. Strawberry was treated 3 times with two concentrations of imidacloprid, and 14 days after the last application residue in strawberry was below 0.2 mg·kg-1.