11.1%吡虫啉缓释片剂在西瓜根区土壤的释放分布及在西瓜中的残留量分析

为了评价11.1%吡虫啉缓释片剂对西瓜蚜虫的防治效果和安全性,于2012—2013年通过田间试验于西瓜移栽时施药,研究了11.1%吡虫啉缓释片剂对西瓜蚜虫的防治效果,及其在瓜秧、果实和土壤中的残留量。结果表明:西瓜苗移栽时将11.1%吡虫啉缓释片剂(吡虫啉有效成分0.08 g/株)施入其根部下方,施药后42 d对西瓜蚜虫的防治效果为83.3%,基本可满足全生育期防治的需要。2012和2013年,11.1%吡虫啉缓释片剂在西瓜采收期(药后/移栽后60 d)的累积释放率分别为15%和32%。与吡虫啉原药处理相比,片剂中的吡虫啉在土壤中的迁移范围较小,药后30 d,施药点下方10 cm外、水平方向6 cm外的吡虫啉残留量低于0.2 mg/kg。此外,施药点下方2~4 cm处、水平方向2~4 cm处土壤中吡虫啉的残留动态基本呈单峰曲线变化,峰值均出现在药后30 d,分别为1.91和0.10 mg/kg;药后120 d分别为0.17和0.03 mg/kg。基部瓜秧中(2012年:0~30 cm;2013年:1~3节)吡虫啉的含量于药后14 d检出,其余时期均未检出;2年试验中,西瓜果实中的吡虫啉残留量均低于最低检测浓度(LOQ)0.05 mg/kg,也低于食品法典委员会(CAC)规定的西瓜中最大残留限量(MRL)0.2 mg/kg。

Release and distribution of 11.1% imidacloprid in root zone of watermelon field soil with applicaton of sustained release tablet formulation and its residue in watermelon

In order to evaluate the control effect of 11.1% sustained release tablet (SRT) of imidacloprid on melon aphid (Aphis gossypii Glover) in watermelon and its application safety to watermelon and environment, the experiments were conducted in open field during growing season of watermelon (Citrullus lanatus) at Beijing in 2012-2013. The 11.1% sustained release tablets of imidacloprid (equivalent to 0.08 g imidacloprid per plant) were applied under the roots of watermelon seedlings while transplanting. The results indicated that the control effect of imidacloprid SRT on melon aphid basically covered the whole growing season (60 d) of watermelon; it was of 83.3% control effect level at 42 d after transplanting/application (DAA) in 2013. The accumulated release ratios of imidacloprid SRT were 15% and 32% at harvest (60 DAA) in 2012 and 2013. The diffusion range of SRT in soils was smaller than that of imidacloprid technical material. At 30 DAA, the residue of imidacloprid SRT in soils beyond 10 cm below application site and beyond 6 cm side of application site were all less than 0.2 mg/kg. Furthermore, the residue dynamic of imidacloprid SRT in the soils 2-4 cm away from the application site in vertical direction and 2-4 cm away in horizontal direction all showed a similar unimodal curve when plotted with the time, with highest values reaching 1.91 mg/kg and 0.10 mg/kg, respectively (all appeared at 30 DAA). At 120 DAA, the residue values of imidacloprid SRT in vertical and horizontal direction were only 0.17 mg/kg and 0.03 mg/kg. In the base of watermelon plants (0-30 cm in 2012, 1-3 internodes in 2013) treated by imidacloprid SRT and TC, the imidacloprid contents were detected at 14 DAA, and imidacloprid contents in the base of watermelon plants in the remaining period were not detected. Imidacloprid residues in whole watermelon, melon rind and melon pulp treated by imidacloprid SRT were all less than LOQ in 2012 and 2013, also lower than the maximum residue limit (MRL) of 0.2 mg/kg set by Codex Alimentarius Commission (CAC).