3种杀虫剂对苜蓿蚜虫和蓟马的防效及其在苜蓿中的残留

为评价10%吡虫啉可湿性粉剂、10%氯氰菊酯乳油和48%毒死蜱乳油对苜蓿蚜虫和蓟马的防治效果和安全性,采用田间喷雾法和气相色谱法测定了3种杀虫剂对苜蓿蚜虫和蓟马的防治效果及其在春季紫花苜蓿中的残留消解动态和最终残留量。结果表明,吡虫啉、氯氰菊酯和毒死蜱在剂量分别为35.7g a.i.(g有效成分)/hm~2、75.0g a.i./hm~2和480.0g a.i./hm~2时,药后1~7d对苜蓿蚜虫的防效为80.83%~94.78%、79.29%~87.80%和90.93%~98.90%;对苜蓿蓟马的防效为78.33%~95.57%、78.56%~91.67%和92.78%~100.00%;在紫花苜蓿中的半衰期分别为4.78,3.69和2.48d。按推荐使用量施药,吡虫啉和毒死蜱药后7d在苜蓿中的残留量均低于0.5mg/kg,氯氰菊酯药后14d在苜蓿中的残留量均低于0.5mg/kg。参照我国和国际食品法典委员会(CAC)农药残留限量要求,拟建议吡虫啉、氯氰菊酯和毒死蜱在紫花苜蓿的最高残留限量(MRL)分别为0.5,1.0和0.5mg/kg,安全间隔期分别为7,14和7d。

Effectiveness of different insecticides for control of aphids and thrips on alfalfa

Imidacloprid 10% wetable powder,cypermethrin 10% emulsifiable concentrate and chlorpyrifos 48%emulsifiable concentrate were compared for their ability to control aphids and thrips on alfalfa;their application safety and environment effects including residual effects were also assessed.Gas chromatography was used to assess chemical residue levels.At 1 -7 days after treatment,the efficacy of imidacloprid,cypermethrin and chlorpyrifos against alfalfa aphids at application rates of 35.7 g a.i./ha (available ingredient/hectare),75.0 g a.i./ha and 480.0 g a.i./ha were 80.83%-94.78%,79.29%-87.80% and 90.93%-98.90%,respectively;against thrips efficacy were 78.33%-95.57%,78.56%-91.67% and 92.78%-100.00%,respectively.The half-life of imidacloprid,cypermethrin and chlorpyrifos were 4.78,3.69 and 2.48 days,respectively.Seven days after application residues of imidacloprid and chlorpyrifos in alfalfa were less than 0.5 mg/kg while cyper-methrin residues did not drop below 0.5 mg/kg until 14 days after application.Based on the pesticide residue standards of the China and Codex Alimentarius Commission (CAC),the maximum residue limit (MRL)of im-idacloprid,chlorpyrifos and cypermethrin were recommended at 0.5,1.0 and 0.5 mg/kg,and the recommen-ded safe application interval 7,14 and 7 days respectively,in alfalfa.