| In order to establish a simple and reliable bioassay method to Bradysia odoriphaga, this experiment evaluated the effects of test factors to the toxicity, including different larval instars, the rearing temperatures and the different rearing diets, and we determined the effects to bioassay results of the insecticide susceptibility of B. odoriphaga to Chlorpyrifos and Clothianidin by stomach-contact toxicity method, artificial diet mixed with agent method and dip method. The results showed that the sensibility of second instar larvae to Chlorpyrifos were 11.9-, 7.4- and 3.3-folds respectively compared with the forth instar larvae measured by the three bioassay methods. For the test insects fed with these four different diets, LC50 of the insects fed on the chinese chive, artificial diet and welsh onion to Chlorpyrifos were 1.84-, 1.47- and 2.31-folds compared with the insects fed on onion. In the range from15℃ to 30℃, LC50 of forth larval instars of B. odoriphaga to Chlorpyrifos increased as the rearing temperature rose. Tested by these three methods, LC50 of forth larval instars to Chlorpyrifos were 67.199 mg/L, 71.123 mg/L, 88.120 mg/L respectively while LC50 of forth larval instars to Clothianidin was 3.584 mg/L, 2.255 mg/L, 4.329mg/L respectively and the fitting degrees of the toxicity curve of stomach-contact toxicity method and artificial diet mixed drugs method were superior to dip method. The study showed that the test insect instars, the rearing temperatures, the different rearing diets had a significant influence on the insecticide susceptibility of B. odoriphaga. The results tested by the stomach-contact toxicity method and artificial diet mixed drugs method were more reliable and accurate than the dip method. |
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