马拉硫磷锐劲特和氯氟氰菊酯对中华稻蝗五龄若虫的急性毒性

Acute Toxicities of Malathion, Fipronile and Cyhalothrin to Fifth Instar Nymphs of Rice Grasshopper Oxya chinensis

采用室内生物测定方法,研究了山西晋源、阳明堡和陕西杨桥镇3个不同地理种群中华稻蝗五龄若虫对马拉硫磷的急性毒性。结果表明,马拉硫磷对3个不同地理种群中华稻蝗的LD50值由低到高依次为:8.14(山西晋源种群)、14.02(陕西杨桥镇种群)和17.35(山西阳明堡种群),且山西晋源种群的毒力回归线斜率b值(4.07113)显著高于山西阳明堡种群(2.62049)和陕西杨桥镇种群(2.86311)的b值。此外,以山西晋源种群中华稻蝗为试验对象,测定并比较了马拉硫磷、锐劲特和氯氟氰菊酯3种农药的急性毒性。3种农药的LD50值由小到大依次为锐劲特(0.12μg·g-1)、氯氟氰菊酯(0.53μg·g-1)和马拉硫磷(8.14μg·g-1),且锐劲特和马拉硫磷的斜率b值(5.19182和4.07113)显著高于氯氟氰菊酯(2.19430)。

As the basic method for studying the toxicity of pesticides and their effect, the bioassay under laboratory conditions plays an important role in research on pest′s resistance to pesticides and its toxicology. In this paper, the acute toxicities of rice grasshopper Oxya chinensis collecting from 3 areas (Jinyuan-SX, Yangmingbu-SX and Yangqiaozhen-SAX) to pesticide malathion were determined. The sensitive order of insect individuals to malathion toxicity in three districts was: Jinyuan-SX (LD50=8.14) >Yangqiaozhen-SAX (LD50=14.02) ≈Yangmingbu-SX (LD50=17.35); and the slope b value of LC-p line of Jinyuan-SX to malathion (4.071 13) was significantly bigger than those of Yangmingbu-SX to malathion (2.620 49) and Yangqiaozhen-SAX to malathion (2.863 11). LD50 values of Yangmingbu-SX and Yangqiaozhen-SAX to malathion was 2.15-fold and 1.72-fold of Jinyuan-SX to malathion, respectively. These results suggested the grasshoppers of Jinyuan-SX was more sensitive to malathion than the grasshoppers of the other two populations, which was consistent with actual conditions that Jinyuan-SX grasshoppers collecting from barnyard grass cluster were less likely to be exposed to pesticides than the grasshoppers of Yangmingbu-SX and Yangqiaozhen-SAX collecting from paddy field. The acute toxicity of malathion, fipronile and cyhalothrin were determined and compared using Jinyuan-SX grasshoppers. The LD50 values of three pesticides were 0.12 μg·g-1 (fipronile), 0.53 μg·g-1 (cyhalothrin) and 8.14 μg·g-1 (malathion), and the slope b values of Jinyuan-SX population to fipronile (5.191 82) and malathion (4.071 13) were remarkably higher than to cyhalothrin (2.194 30), which indicated the acute toxicity and consistency of Jinyuan-SX individuals to fipronile was the highest. That LD50 value of Jinyuan-SX individuals to cyhalothrin was relatively little and the individual consistency was obviously lower indicated there probably existed resistant individuals to cyhalothrin in the natural population. Though LD50 value (8.14 μg·g-1) of Jinyuan-SX individuals to malathion was higher than those of fipronile and cyhalothrin, the slope b value (4.071 13) was close to that of Jinyuan-SX to fipronile, indicating the similar higher consistency of Jinyuan-SX individuals to malathion and fipronile. The higher concentration of pesticide malathion, the more mortality of the insect individuals.