Studies On Toxicity Of Several Insecticides And Controlling Efficiency Of Bait Against Solenopsis Invicta Buren

The red imported fire ant Solenopsis invicta Buren,which was found in mainland China in 2004,is a significant dangerous invasive species in the world.S.invicta has spread to thirteen provinces and regions in south China.Chemical insecticides are widely used to controlling S.invicta.The development and application of new insecticides is the basis and guarantee for controlling fire ant continuously and effectively.In this thesis,contact toxicity,stomach toxicity and transfer toxicity of insecticides were screened by bioassay.Based on the screening results,further studies on controlling efficiency of clothianidin,nitenpyram and thiamethoxam baits under laboratory and foraging behavior in the field were conducted.This research provides reference for future development and application of new powder or bait in fire ant control.The results were as follows:1.The contact and transfer toxicity of eight insecticides against S.invicta workersThe contact and transfer contact toxicity of eight insecticides against S.invicta major workers was determined.The results showed that clothianidin,thiamethoxam,dinotefuran and ethiprole had a high toxic effect against workers,and their LD₅₀ values were 0.0019μg/worker,0.0020μg/worker,0.0021μg/worker and 0.0031μg/worker,respectively.And the transfer contact toxicity showed that the mortality rates of insecticide recipients increased with the increasing of the mortality rates of insecticide donors.We found that clothianidin,thiamethoxam and dinotefuran showed an obvious toxic effect.After treated with 3.365μg/mL clothianidin,4.481μg/mL thiamethoxam,and 6.997μg/mL dinotefuran five days later,the mortality rates of recipients were 100%,98.52%and 90.37%,respectively.Base on the above results,clothianidin could be suitable candidate insecticide for S.invicta control.2.The oral toxicity and transfer of five neonicotinoid insecticides against S.invictaThe oral toxicity of five neonicotinoid insecticides against S.invicta workers was determined.The results indicated that the LC₅₀ values of dinotefuran,clothianidin,nitenpyram and thiamethoxam were 0.6006μg/m L,0.8777μg/mL,1.0464μg/m L and1.1063μg/mL,respectively.Then,further studyies were conducted to evaluate the transfer toxicity of the insecticides among different castes of S.invicta.The results showed that after treated with 1.106μg/mL thiamethoxam three days later,the mortality rate of male alates was 100%.After treated with 0.878μg/mL clothiandin and 1.106μg/mL thiamethoxam seven days later,the mortality rates of female alates were all 100%.And after 5 days treated with four insecticides,the mortality rates of males were all 100%.In the 8th day,the mortality rates of larvaes were all 100%.In the 9th day,the mortality rates of female alates were all 100%.It showed that the lethal concentration of 50%of dinotefuran,clothianidin,nitenpyram and thiamethoxam also have a good oral tocixity against other castes of S.invicta.3.The effects of bait in laboratory condition against S.invictaEffects of bait with clothianidin,nitenpyram and thiamethoxam were examined under laboratory condition.Results showed that 128μg/g clothianidin,500μg/g nitenpyram and128μg/g thiamethoxam baits were toxic to workers and larvaes of S.invicta.After treated with toxic bait ten days later,the mortality rates of workers were more than 90%,and the mortality rates of larvaes were between 50%and 70%.4.The sduties of foraging behavior on bait in the field against S.invictaForaging activities of S.invicta on different toxic baits in the field were examined.The results showed that recruit companions quantities and bait retrieval qualities from workers were lower than that of control.The study showed that clothianidin,dinotefuran and thiamethoxam had a strong contact toxic effect against S.invicta.They could be a suitable candidate insecticide to develop into contact powder insecticide for controlling S.invicta.Meanwhile,clothianidin,nitenpyram and thiamethoxam have stomach toxic effect on S.invicta.Although bait containing either the three insecticides has a good toxic effect to workers and larvaes of S.invicta,we found workers avoid choosing these baits.Therefore,it implied that the three insecticides are not suitable to develop into solid bait for S.invicta control.