噻虫嗪对田间麦蚜种群防控效果与残留消减动态的关系

为评价噻虫嗪在小麦生产上应用的安全性,本研究进行了21%噻虫嗪悬浮剂对田间麦蚜的防控试验,并测定了噻虫嗪在小麦植株及籽粒中的残留。结果表明:21%噻虫嗪SC 23.625 g/hm~2防治麦蚜效果最佳,药后3 d,对麦蚜相对防效可达到91.48%,其次为21%噻虫嗪SC 15.75 g/hm~2,药后3 d,相对防效可达到87.48%,且与噻虫嗪23.625 g/hm~2差异不显著。残留消解动态检测结果表明,在小麦抽穗期施用21%噻虫嗪SC 15.75 g/hm~2防治小麦蚜虫,在小麦植株中的半衰期为4.8 d,药后14 d消解92%,半衰期较短,消解速度较快。最终残留试验表明,21%噻虫嗪SC,用药量15.75～23.625 g/hm~2,小麦生长后期连续施药1～2次,最后一次用药后7、14、21 d采收的小麦籽粒中未检出噻虫嗪(0.01 mg/kg)。建议用21%噻虫嗪SC防治小麦蚜虫,最高制剂用药量75 g/hm~2(有效成分15.75 g/hm~2),在小麦抽穗期施药一次,安全间隔期14 d。

Relationships between the control effect on aphid populations and theresidue decline dynamics of thiamethoxam in wheat fields

To assess the safety of thiamethoxam in wheat, we designed the control effect experiment of 21% thiamethoxam 21% SC against wheat aphids in fields and detected the residue of thiamethoxam in wheat plants and the grains. The results showed that thiamethoxam 21% SC (23.625 g/hm2) was the best, and its relative control effect was 91.48% at 3 d after spraying. The relative control effect of thiamethoxam 21% SC (15.75 g/hm2) amounted to 87.48% at 3 d after spraying. The difference was not significant in the relative control effect between the two dosages of thiamethoxam (23.625 g/hm2 and 15.75 g/hm2). We investigated the residue dynamics of thiamethoxam 21% SC in wheat plants during heading period. The results showed that the decomposition half-life of thiamethoxam (15.75 g/hm2) 21% SC was 4.8 d in wheat plants. Thiamethoxam was removed by 92% after 14 d. It had a short half-life and faster degradation speed. The results of residue experiments indicated that, when the dosage of thiamethoxam 21% SC ranged from 15.75 to 23.63 g/hm2 (continuous spraying 1-2 times at later growth stage of wheat), no thiamethoxam residues could be detected from wheat grains at 7, 14, 21 d after the last spraying (residues< 0.01 mg/kg). It was suggested that the highest dosage of thiamethoxam 21% SC for controlling wheat aphids was 75 g/hm2 (effective constituent: 15.75 g/hm2) by spraying one time during heading stage, and the chemical safety interval period was 14 d.