Effects Of Flubendiamide On The Parastism Potential Of Diadegma Semiclausum (Hymenoptera:Ichneumonidae),A Parasitoid Of The Diamondback Moth

Diadegma semiclausum is the dominant parasitic wasp of the larval stage of vegetable pest Plutella xylostella,but it is sensitive to insecticides.There are few studies have shown that not only high toxic insecticides have safety risks on the wasp,but also fungicides have adverse effects.Screening insecticides with low toxicity to the wasp is important for IPM of Plutella xylostella,but safety risk of low toxicity insecticides should not be neglected.Therefore,the safety of six insecticides to the wasp which commonly used in vegetable fields had been determined first,and then the flubendiamide was chose to study the safety of ecology and biochemistry to the wasp continue in order to provide a theoretical basis for the rational application of the insecticides.The following are results of this study:(1)Acute toxicity of six insecticides to Diadegma semiclausum.The contact toxicity of 6 insecticides against adults of Diadegma semiclausum was tested by vial residual film method.The results showed that the orders of toxicities of tested insecticides to the wasp were thiamethoxam > sulfoxaflor > imidacloprid > acetamiprid > spirotetramat > flubendiamide.The LC50 values of the first 4 kinds of insecticides were 0.0619,0.689,2.821 and 4.173 mg/L,respectively.Spirotetramat and flubendiamide showed the lowest toxicities to the wasp with LC50 values of > 2000 mg/L.And thiamethoxam and sulfoxaflor had extremely high risk to this wasp with safe factors of 0.00077 and 0.0069,respectively.Imidacloprid and acetamiprid with safe factors of 0.067 and 0.13,respectively,were high risk to the wasp.Spirotetramat and flubendiamide showed low risk with safe factors of > 5.In addition,thiamethoxam,sulfoxaflor,midacloprid and acetamiprid are all risk to the wasp after expose by intake and during pupal stage.While spirotetramat and flurbadimide had no effect to the wasp and were safe to pupae.(2)Efect of flurbadimide on parasitism rate and offspring development of Diadegma semiclausumIn general,development,emergence and sex ratio of offspring were not affected by the insecticide no matter how exposedd.There were no significant differences in parasitic rate between the parents of the treated group and the control group after the insecticides were ingested and exposed during pupal stage.However,it should be noted that the parasitism rate of the third instar of the parent wasps was significantly reduced after exposure to flurbadimide;however,the parasitism rate of the treated group was only reduced by 10.77%.This further proves that flurbadimide has a certain effect on Diadegma semiclausum,but the effect is acceptable.(3)Effect of flurbadimide on functional response and searching effect of Diadegma semiclausum.Structure of the functional response of female wasps to the 3rd instar larvae of Plutella xylostella remained unchanged,just reduced a and prolonged Th values,and had little effect on the functional response of parasitoids compared with the control,especially in pupal stage.At the same time,three exposure routes sensitized to flurbadimide reduced the search effect of Diadegma semiclausum on the 3rd instar larvae of Plutella xylostella.This indicated that the insecticides had a certain effect on parasitic ability of parasitoids,but the effect was very small.In addition,the effect of flurbadimide on parasitoids of F1 generation was lower than that of their parents through three exposure routes,which proved that the transgenerational effect of flurbadimide on Diadegma semiclausum curvature wasps was not enough to threaten the control ability of semi-closed curvature wasps.(4)Effect of flurbadimide on detoxification enzymes activity of Diadegma semiclausum.The activity results of detoxification enzymes(EST,GST,MFOs)showed that there was no significant effect to the wasp when exposed to flurbadimide during pupal stage.However,the recommended dose of fluorodiamide had some effect on the detoxification enzymes of Diadegma semiclausum when exposed to the insecticide by another way.Effect of flurbadimide on esterase activity was mainly inhibited,of which the most significant was the way which wasp was fed and contacted of flurbadimide.The activity of glutathioneS-transferase was always inhibited after exposure to flurbadimide by contact,and the activity of glutathioneS-transferase after intake of flurbadimide showed a trend of activation first and inhibition after.The effect of flurbadimide on the activity of multifunctional oxidase was as follows: contacted first inhibited the activity of multifunctional oxidase,then activated,and finally continued to inhibit;while intaked only significantly inhibited the activity of multifunctional oxidase at 24 hours after treated.Generally,the inhibition of esterase activity by insecticide may reduce the sensitivity of parasitoid so that reduced conduction of nervous system,thus making them insensitive to diamondback moth than affecting their search for Plutella xylostella.The increased activity of glutathione-S-transferase degraded the residual pesticide in parasitoids,which may be the reason why the search effect of F1 generation was not affected after intaked of fluorofenamide.In addition,the activation of glutathione-S-transferase and multifunctional oxidase may be the reason for the lower acute toxicity of the fluorofenamide to Diadegma semiclausum.