Determination of the indoor insecticidal activity and toxicity of eight insecticides against the larvae of the fall armyworm Spodoptera frugiperda
In order to screen the effective insecticides for the control of the larvae of the fall armyworm Spodoptera frugiperda,the indoor insecticidal activity and toxicity of eight insecticides against the larvae of the fall armyworm S.frugiperda were determined by leaf dipping method using the newly hatched and 3rd instar larvae of the fall armyworm S.frugiperda as the test materials.The results showed:the corrected mortality rates of the eight insecticides were 100％ against the newly hatched larvae of the fall armyworm S.frugiperda at 72 h after the lowest recommended in the field dose and 96 h after the 3rd instar larvae at the highest recommended in the field dose,and all of them had good insecticidal activity.In the indoor toxicity assay,10％ Spinosad emamectin benzoate WG and 5％ Emamectin benzoate WG were more toxic to the newly hatched larvae of the fall armyworm S.frugiperda,with LC50 values of 0.0108 mg/L and 0.0109 mg/L,and 0.0091 mg/L and 0.0077 mg/L at 24 h and 48 hafter treatment,respec-tively.The highest relative toxicity of 5％ Emamectin benzoate WG was observed against 3rd instar lar-vae,with LC50 values of 0.0246 mg/L and 0.0179 mg/L at 24 h and 48 h after treatment,respectively.The LC50 values of all eight insecticides for the newly hatched larvae and 3rd instar larvae of fall armyworm S.frugiperda showed that the LC50 values of the same insecticide for newly hatched larvae were less than the LC50 values of 3rd instar larvae treated at the same time,and the LC50 value of the same insec-ticide treated for 48 h was smaller than that of the treatment for 24 h;the indoor insecticidal activity and toxicity determination showed that the newly hatched larvae of the fall armyworm S.frugiperda had a weaker resistance to the insecticides than the 3rd instar larvae.The resistance of the newly hatched lar-vae to the insecticides was significantly weaker than that of the 3rd instar larvae,recommended for use in the early stages of larvae monitoring.the lower LC50 values and higher relative virulence of 5％ E-mamectin benzoate WG and 10％ Spinosad emamectin benzoate WG,which were suitable for use when the population density of the fall armyworm S.frugiperda was high or when there were outbreaks,and the other 6 insecticides could be used as the recommended insecticides when the population density was low.
NETL
NSTL
万方数据
维普
