Sublethal Effect Of Broflanilide On Spodoptera Litura And Eocanthecona Furcellata

Spodoptera litura,one of the three major pests in tobacco fields,is having an increasingly serious impact on the development of the tobacco industry.At present,lepidopteran pests on tobacco are still mainly controlled by chemicals.The excessive and unscientific use of chemical insecticides can cause serious environmental problems and even threaten human health.Natural enemies are a potential natural renewable resource in agricultural ecosystems and play an increasingly important role in tobacco and agricultural farming.Eocanthecona furcellata is an important predatory natural enemy insect in agricultural systems,with strong predatory ability on lepidoptera larvae in tobacco fields,and has great potential for application in tobacco ecosystems.Nevertheless,chemical agents still occupy an important position in pest control due to their quick-acting and economic characteristics,while natural enemy insects often have unstable pest control effects due to abiotic stress and chemical stress,therefore,it is of great importance to improve the compatibility of chemical and biological control and to combine them.In this thesis,the toxicity measurement of four chemical agents was determined by leaf-dipping method in lab,and the agents with high insecticidal activity against S.litura were screened and their sublethal effects were clarified;the effects of sublethal doses of the agents on the biological characteristics of E.furcellata such as development and predation were compared by spraying and feeding treatments,and the detoxification enzymes of E.furcellata were clarified.The main results were as follows:1.Sublethal effect of broflanilide on Spodoptera lituraThe indoor virulence of four insecticides,broflanilide,methylamino avermectin benzoate,chromafenozide and tetraniliprole,against S.litura 3^rd instar larvae was determined using leaf impregnation to screen for agents.The results showed that after 24h of treatment,the escending order of virulence was:100 g/L broflanilide SC>200 g/L methylamino avermectin benzoate SC>200 g/L tetraniliprole SC>5%chromafenozide SC,it is clear that broflanilide has high insecticidal activity against S litura.The developmental period of larvae of all ages from 3^rd to 6^th of the S.litura F₀ generation was significantly prolonged after treatment with broflanilide at sublethal concentrations,the average daily feed intake of 3^rd to 5^th instar larvae was significantly reduced,and the pupal weight was reduced,the pre-oviposition period was significantly increased,and the number of eggs laid and the total number of eggs laid were significantly reduced,however,the pre-pupal stage,pupal stage,pupation rate,fledging rate,and adult longevity were not significantly different from the control group.The total developmental period of F₁generation larvae was significantly longer than that of the control group,the cumulative survival rate was reduced,and the feeding rate of 5^th instar larvae was significantly lower,the weight of male pupae,the number of eggs laid,and the total number of eggs laid were all significantly lower than that of the control group.2.Effects of sublethal doses of broflanilide on the biological characteristics of Eocanthecona furcellataThe effects of sublethal concentrations of broflanilid on the 2^nd-5^th instars of E.furcellata and the F₀ and F₁ generations of female adults were determined by spray treatment and feeding of gastric poisoning treatments.The survival rate of the F₀generation in the spray treatment was lower than that of the control,except for the 2^ndinstar,and the survival rate of the F₁ generation at all ages was lower than that of the control.The development of the E.furcellata F₀ generation after the spray treatment showed an overall prolongation with the developmental period of the 2^nd instars was significantly prolonged in the 2^nd instar treatment,the 4^th and 5^th instars in the 4^th instar treatment,and the total developmental period of the F₁ generation was prolonged in all but the 3^rd instar treatment.The number of eggs laid by the spray treated F₀ generation at any age after E.furcellata development to adulthood were significantly reduced,and the egg hatching rate of the F₁ generation was reduced,with no significant difference in the number of days of egg hatching from the control except for the egg dipping treatment.The developmental periods of the F₀ generation at all ages and the total developmental periods of the F₁ generation were prolonged compared with the control by feeding the gastric poisoning treatment to the 2^nd-5^th instars of E.furcellata.Survival was suppressed,the pre-laying period was significantly longer,the number of ovipositions and the total number of eggs laid were significantly lower,the hatching rate of the F₁ generation eggs was significantly lower and the number of days to hatch was not significantly different from that of the control.3.Analysis of predation function response of Eocanthecona furcellata under sublethal dose of broflanilidespraying treatment and feeding gastric poisoning treatment of E.furcellata 2^nd to 5^thinstar wakes,determination of the predatory function response of E.furcellata 2^nd to 5^thinstar wakeflies to S.litura 3^rd instar larvae.The results showed that the functional response were all Holling type II for both the treatment and control.The theoretical maximum daily predation rates of the 2^nd to 5^th instars in the spray treatment was less than that of the control indicating the feeding ability of E.furcellata was negatively affected.However,the maximum daily predation and instantaneous attack rate of stomach-toxic-treated E.furcellata 2^nd to 5^th instar increased,while the handling time was decreased.The results showed that the sublethal doses of broflanilide stomach-toxic treatment of S.litura had a facilitative effect on the predatory ability of E.furcellata larvae.4.Analysis of changes in Eocanthecona furcellata detoxification enzyme activity after sublethal doses of broflanilideThe activity of the key detoxifying enzymes including CarE and GST were measured24 h after treated E.furcellata 2^nd-5^th instars by spraying and feeding gastric poisoning treatment.The expression of CarE activity in 2^nd instars was inhibited after being sprayed with broflanilide,but promoted in 3^rd-5^th instars.The expression of GST activity in 2^nd-5^th instars of E.furcellata significantly increased.CarE activity in 2^nd-5^th instar of E.furcellata and GST activity in 2^nd-4^th instar of E.furcellata significantly increased after the feeding gastric poisoning treatment.In summary,this study screened and clarified that broflanilide is a chemical agent with high insecticidal activity against S.litura,and evaluated the effects of sub-lethal effects of broflanilide on the biological characters of S.litura and its natural enemy E.furcellata at the biological level.Behavioral studies were conducted to estimate the predation of E.furcellata treated with sublethal dosage of broflanilide on S.litura.Detoxification enzyme activity changes in E.furcellata under sublethal doses were measured at the physiological level.The study has systematically assessed the safety of the chemical insecticide broflanilide on natural enemies E.furcellata,providing technical support for the combined application of chemical and biological control in tobacco systems,which is important for the sustainable development of the tobacco industry.