| Amblyseius cucumeris(Oudemans)is a beneficial non-target arthropod(NTA)and a key predator of tetranychid mites such as Tetranychus cinnabarinus and Tetranychus urticae in integrated pest management(IPM)programs across China.In recent years,the intensive use of pesticides has led to extremely negative effects in agriculture crops.The substantial use of insecticides affects not only their natural target organisms but also other non-target arthropods,such as A.cucumeris.Therefore,it is very important to evaluate the risk of pesticides on the A.cucumeris,and to screen highly selective pesticides for NTAs and target pests,so as to achieve the reduction of pesticides,and to protect the biological function and ecological environment of NTAs.In this study,the toxicity response difference of A.cucumeris and its prey,T. cinnabarinus were tested after exposed to 25 kinds of common pesticides.The ecological risk of pesticides to A.cucumeris were evaluated using the HQ(hazard quotient)approach and the the sensitive position of A.cucumeris in NTAs was determined using the species sensitivity distribution model.Finally,We found that emamectin benzoate is highly selective to NTAs and target pests,and it has low risk to the ecological environment.On this basis,in order to explore the mechanism of the stress effect of emamectin benzoate to A.cucumeris,a life table model was established to obtained growth and development parameters,and evaluated the long-term toxic effect of emamectin benzoate on A.cucumeris from the perspective of population.The stress effects were analyzed from the biochemical point of view through epidermal penetration and enzyme activity measurement.The genes and metabolic pathways corresponding to the expression of metabolic enzymes and protective enzymes were found by transcriptome and metabolome.This research results have a good guiding role in the research and development of related pesticide varieties,and the research of domestic and foreign pesticides on NATs from macro to micro,from system to specific methods.The main research contents and conclusions are as follows:(1)The toxic effects of 25 different pesticides on A.cucumeris and Tetranychus cinnabarinusThere were significant differences in the pesticides resistance of A.cucumeris and T.cinnabarinus to abamectin and emamectin benzoate,with the difference multiples reaching 883 and 622;the selectivity of five neonicotionoids to two kinds of test insects was not obvious,with the difference multiples around 0.58-2.00;the selectivity of organophosphorus insecticides dimethoate and malathion to two kinds of test mites was opposite;The toxicity of pyrethroids was about 0.04-2.37 times,and most of them were more toxic to A.cucumeris;the toxicity difference of spirodiclofen,spirotetramat,fipronil,tolfenpyrad and pyridaben was about 2 times,and the selectivity was also not obvious.In conclusion,the avermectins showed the highest selectivity to A.cucumeris and T.cinnabarinus.(2)The ecological risk assessment of 25 kinds of pesticides on A.cucumerisIn the in-field exposure scenario,avermectins and neonicotionoids showed low risk(HQ<5),organophosphorus and pyrethroids showed high risk(HQ>5).In the off-field exposure scenario,most of the insecticides showed a low risk to the A.cucumeris,but the risks of bifenthrin and malathion could not be ignored;some acaricides,such as spirodiclofen,spirotetramat,tolfenpyrad and pyridaben,were low risk agents.(3)The species sensitivity distribution of 13 NTAs to 5 different pesticidesThe sensitivity of 13 NTAs to 5 insecticides was different,which showed that the sensitivity of NTAs to dimethoate,bifenthrin and imidacloprid was higher than that of abamectin and emamectin benzoate.Among the parasitic natural enemies,Trichogramma dendrolimi is more sensitive than T.chilonis,and T.ostriniae,but the sensitivity of Aphidius gifuensis is worse.In predatory natural enemies,the sensitivity of Coccinella septempunctata is higher than that of predatory mites and orius.T.dendrolimi and C.septempunctata are recommended as the indicator species of NTAs in China.In the aspect of low-risk pesticide selection,emamectin benzoate can control more than 80%of pests at low dose,and its potentially affected fraction on NTAs is 32.5%,which can be used as a combination of high-efficiency selective agent to minimize the negative effects of pesticides.(4)The effects of emamectin benzoate on the growth,development and population parameters of A.cucumeris by constructing life Tab.With the increase of the dose of emamectin benzoate,the life span and the early stage of oviposition of A.cucumeris were shortened,and the oviposition of female mites was reduced.The net increment rate(R0)and the average generation cycle(T)of A.cucumeris decreased.The intrinsic increment rate(R)and the weekly increment rate(?)did not decrease significantly.Although the population growth of emamectin benzoate was lower than that of the blank control,it showed an increasing trend on the whole,and male mites were more susceptible than female mites.(5)The effects of emamectin benzoate on the penetration of epidermis and the induction of related enzyme system of A.cucumerisThe results showed that the penetration of epidermis was not the main reason for the sensitivity difference between A.cucumeris and T.cinnabarinus;The specific activities of GST,Car E,Ach E and POD decreased with the increase of the concentration of emamectin benzoate,and the protective enzymes activities of SOD and CAT increased under the stress of emamectin benzoate.The results showed that SOD and CAT were involved in the protection mechanism of physiological activities of A.cucumeris.(6)Transcriptome analysis of A.cucumeris under the stress of emamectin benzoateThe results of transcriptome differential expression showed that there were 1035 genes showed different expression levels between blank control and the group of after treatment of emamectin benzoate,among which 510 were up-regulated genes and 525 were down-regulated genes.There are 1,1 and 2 up-regulated genes in P450,GST and Ach E families,5,12 and 2 down-regulated genes respectively,one down-regulated gene in Car E family,no up-regulated gene;one up-regulated and down-regulated gene in POD family;two up-regulated in SOD family,one up-regulated in cat family;three up-regulated and down-regulated in target gene gabacl;two up-regulated genes in glucl.q-PCR was used to verify the target gene,and the results were consistent with each other.(7)Metabonomics analysis of A.cucumeris under the stress of emamectin benzoateDifferential metabolites of A.cucumeris under emamectin benzoate stress were analyzed by liquid chromatography-mass spectrometry(LC-MS).A total of 318annotated metabolites were detected,79 of which had different metabolites,33 of which were up-regulated and 46 of which were down-regulated.We used principal component anlaysis(PCA)and orthogonal projections to latent structures-discriminant analysis(PLS-DA)to anslysis different metabolites,and found there were significant differeces between blank control and treatment group.The main differential metabolites were 8,9-EET,CMP and Oxoadipic acid,etc.The main differential metabolic pathways were Aminoacyl-t RNA biosynthesis,phenylalanine metabolism and nitrogen metabolism,etc. |
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