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对饲料混合法 ,体重抑制率法 ,浸叶接虫法进行比较研究 ,结果表明 ,饲料混合法比较稳定 ,比较适宜作为抗性测定的方法。用饲料混合法测定比较不同龄期幼虫的测定结果 ,确定 2龄作供试幼虫为宜。比较不同处理天数下的生测结果 ,确定 Bt粉剂对 2龄幼虫的适宜处理时间为 5d,Cry1Ac为 14d。用改进稀饲料隔离饲养供试幼虫的方法后 ,得到理想的生测数据 ,生测时间延长到 14d,对照死亡率也能控制在 2 0 %以下。从我们 1998年对棉铃虫的抗性监测结果说明 ,尽管田间棉铃虫对 Bt ICP未达抗性水平 ,但对 Cry1Ac型蛋白敏感性已有降低 ,值得引起重视
The results showed that the feedstuff mixed method was relatively stable and suitable for the determination of resistance. The results of the determination of the larvae of different ages by the method of feed mixing determined that the 2nd instar larvae should be used as test larvae. The results of biopsy under different treatment days were compared. The optimum treatment time of Bt powder for 2nd instar larvae was 5 days and that of Cry1Ac was 14 days. With the improved method of isolation of lean feed for feeding larvae, the ideal bioassay data was obtained. The test time was prolonged to 14 days and the control mortality could be controlled below 20%. From our monitoring of the resistance to H. armigera in 1998, the sensitivity to Cry1Ac type protein has been reduced despite the underexposure to Bt ICP in the field and deserves attention