Risk of control failure to insecticides malathion,profenophos+cypermethrin mixture,and fipronil in boll weevil(Coleoptera:Curculionidae)populations from Bahia,Brazil

Background To control the boll weevil Anthonomus grandis grandis(Coleoptera:Curculionidae),a key pest of cotton in the Americas,insecticides have been intensively used to manage their populations,increasing selection pressure for resistant populations.Thus,this study aimed to detect insecticide resistance and assess insecticide control failure likelihood of boll weevil populations exposed to malathion,profenophos+cypermethrin,and fipronil insecticides.Results Twelve populations of the boll weevil were collected from commercial cotton fileds of the state of Bahia,northeastern Brazil.These populations were exposed to malathion,profenophos+cypermethrin mixture,and fipronil,at their respective maximum label dose for field applications.Three replicates of 10 adult beetles were exposed to the insecticides and mortality was recorded after 24 h treatment.The control failure likelihood was determined after 48 h.Highest median lethal times(LT_(50))were observed for malathion and the profenophos+cypermethrin mixture.Resistance to at least one insecticide was detected in 11 populations;three populations were resistant to malathion and profenophos+cypermethrin;seven were resistant to all insecticides tested.The resistance levels were low(<10-fold)for the three insecticides.Among 12 populations tested,58%of them exhibited significant risk of control failure for the insecticides malathion and profenophos+cypermethrin.The insecticide fipronil was efficient for the control of the boll weevil in 83%of the populations.Conclusions The results confirm the significant risk of insecticide control failure in the boll weevil populations to the main compounds used in the region.Thus,proper insecticide resistance management plans are necessary for the boll weevil in the region,particularly for malathion and profenophos+cypermethrin insecticides.

Indoor Efficacy Experiment of 13 Insecticides against Tea Geometrid (Ectropis Oblique Hypulina Wehrli)

[Objective]The paper was to study indoor efficacy of 13 insecticides against tea geometrid（Ectropis Oblique Hypulina Wehrli）.[Method]Thirteen insecticides were sprayed onto indoor hydroponic young tea shoots with infesting third instar larvae of tea geometrid reared in the laboratory to simulate the actual condition in the tea garden,and their efficacy was studied.[Result]The control efficacies of 60 g/L spinetoram SC 3 000 times dilution,3% emamectin benzoate ME 15 000 times dilution,240 g/L methoxyfenozide SC 5 000 times dilution and 240 g/L metaflumizone SC 1 500 times dilution were all greater than 91% after spraying for 7d.The control efficacy of 20%tebufenozide SC 1 000 times dilution remained 86.48%.Although the control efficacy of 20%flubendiamide WDG 6 000 times dilution was slightly lower than the above five treatments,the dry weight of faeces was the second least,and its protection effect on leaves was only second to spinetoram.Therefore,60g/L spinetoram SC,3% emamectin benzoate ME,240 g/L methoxyfenozide SC,240 g/L metaflumizone SC,20% tebufenozide SC and 20% flubendiamide WDG were ideal insecticides that could be used rotationally to control tea geometrid in tea garden.The control efficacy of 10% bifenthrin EC 3 000 times dilution was only 23%,so the insecticide was not suitable for control against the pest.[Conclusion]The paper proposed an alternate insecticide for field control against tea geometrid.