Abstract:

【Objective】Previous studies showed that vetiver grass (Vetiveria zizanioides) can effectively attract female adults of Sesamia inferens (Walker) and Chilo suppressalis (Walker) to lay eggs, while hatched larvae will die after feeding on vetiver grass for a certain time. Therefore, vetiver grass is recommended for field control of rice stem borers. However, the combination of various measures is always used for field control. At present, chemical control is still an irreplaceable measure. Nevertheless, the sensitivity change of rice stem borers after feeding on vetiver to commonly used insecticides is still unclear. 【Method】Seedling dipping bioassay method was used to investigate the toxicity of eight insecticides, including indoxacarb, chlorantraniliprole, spinosad, emamectin benzoate, sulfluramid, metaflumizone, abamectin and chlopyrifos to both S. inferens and C. suppressalis, and the sensitivity changes of these two insect species to these insecticides after feeding on vetiver grass. 【Result】 LC₅₀ to S. inferens were as follows: metaflumizone 1.04 mg/L, emamectin benzoate 1.40 mg/L, chlorantraniliprole 2.67 mg/L, sulfluramid 3.48 mg/L, spinosad 7.59 mg/L, abamectin 13.03 mg/L, indoxacarb 16.57 mg/L, chlorpyrifos 23.28 mg/L; and to C. suppressalis were metaflumizone 1.94 mg/L, emamectin benzoate 2.07 mg/L, chlorantraniliprole 4.20 mg/L, sulfluramid 8.93 mg/L, indoxacarb 9.51 mg/L, spinosad 9.72 mg/L, abamectin 17.63 mg/L, chlorpyrifos 64.68 mg/L. The sensitivity of the two kinds of rice stem borers fed on vetvier grass was increased as compared with the stem borers fed on rice. Three days after feeding on vetiver grass, the sensitivity of S. inferens larvae to eight pesticides was improved, and the mortality was also increased by 13.3%-22.2%. The sensitivities of S. inferens to chlorantraniliprole, spinosad, sulfluramid, metaflumizone and chlorpyrifos were significantly increased, while the sensitivity of C. suppressalis larvae to all the tested pesticides was significantly increased after feeding on vetiver grass with an increased mortality by 26.7%-33.3%. Overall, the sensitivity of C. suppressalis larvae was obviously increased more than that of S. inferens. 【Conclusion】The sensitivity of rice stem borers to eight commonly used insecticides was dramatically increased after feeding on vetiver grass.

Key words: Sesamia inferens, Chilo suppressalis, vetiver grass, insecticides, sensitivity, bioassay

摘要：

【目的】香根草能有效诱集水稻螟虫产卵,且孵化的幼虫取食香根草一定时间后死亡,可用于水稻螟虫的田间防控。但田间防治往往是多种防治措施相结合。为了研究取食香根草后的幼虫对常用杀虫剂的敏感度,【方法】利用稻苗浸渍法测定了茚虫威、氯虫苯甲酰胺、多杀菌素、甲氨基阿维菌素、氟虫胺、氰氟虫腙、阿维菌素、毒死蜱8种常用杀虫剂对水稻大螟和二化螟的毒力作用,以及取食香根草后螟虫对这些药剂的敏感度变化。【结果】8种杀虫剂(氰氟虫腙,甲氨基阿维菌素,氯虫苯甲酰胺,氟虫胺,多杀菌素,阿维菌素,茚虫威,毒死蜱)对大螟的LC₅₀依次为1.04,1.40,2.67,3.48,7.59,13.03,16.57,23.28 mg/L;对二化螟的LC₅₀依次为1.94,2.07,4.20,8.93,9.72,17.63,9.51,64.68 mg/L。与取食水稻的螟虫比较,香根草饲喂3 d后,大螟幼虫对8种药剂的敏感性均有所提高,致死率提高13.3~22.2个百分点,其中,对氯虫苯甲酰胺、多杀菌素、氟虫胺、氰氟虫腙、毒死蜱的敏感度显著提高;而香根草饲喂后的二化螟幼虫对所有测定药剂敏感度均显著提高,致死率提高26.7~33.3个百分点。二化螟幼虫对所有测定药剂敏感度升高更为明显。【结论】初步明确了水稻螟虫取食香根草后对杀虫剂的敏感度有不同程度提高。

关键词: 二化螟, 大螟, 香根草, 杀虫剂, 敏感度, 抗药性