Predation Of Menochilus Sexmaculata (Fabricius) On Vigna Unguiculata (Linn.) Walp Insect Pests And Its Molecular Detection

Hainan is located in the tropical subtropical region,the annual suitable for crop growth and it is called"natural greenhouse",which is an important production base of winter fruits and vegetables in China.The area of cowpea reached 13,300 hm~2and the production is about 250,000 tons every year in Hainan.It is an important economic source of local specialty economy and it also the source of income for farmers.However,the serious occurrence of pests in cowpea fields and it has become an important factor limiting the development of the cowpea industry.For a long time,the local community relies mainly on chemical pesticides to control pests on cowpeas.However,due to the long-term use of pesticides had result increasingly resistance to pests,and the problem of the pest re-rampant is serious.Therefore,using predatory natural enemies insects to control pests is an important thing at present.In this study,we conduct the species of insect to know the main pest species in local cowpea fields.Further,we assessed the predation of Menochilus sexmaculata on pests of cowpea fields.At the same time,by using the technology of COⅠtesting to assessed the predation of Menochilus sexmaculata on main pests in field,laying the foundation for future applications.The results of the study,from both indoor and field levels to elucidate the control of major pests in cowpea fields by Menochilus sexmaculata.On this basis,to control of cowpea pests by using natural enemy insects.The results of the study are as follows:1.The field surveys showed that Megalurothrips usitatus and Aphis craccivora which are the largest number of pests.Among them,Megalurothrips usitatus had the largest number,in a single plant reached 203 head/m~2.It accounted for 44%of the total population.Aphis craccivora was the next most abundant,make up 19%.And their are other pests also occur,for example Liriomyza sativae,Etiella zinckenella,Bemisia tabaci and so on.Their numbers were lower compared to Megalurothrips usitatus and Aphis craccivora.During the survey,we also find that Menochilus sexmaculata has a large number and it was the dominant natural enemy in the area,in a single plant,it can reached11 head.2.By studying that use of predatory natural enemies Menochilus sexmaculata prey on Megalurothrips usitatus and Aphis craccivora in laboratory,we found that Menochilus sexmaculata prey on Megalurothrips usitatus and Aphis craccivora with strong predatory ability.And the functional responses of the predation of Menochilus sexmaculata on Megalurothrips usitatus and Aphis craccivora belong to HollingⅡtype.And its adult can prey more pests.For examples,it can feed Megalurothrips usitatus larve 714.20 head and500.00 head of Aphis craccivora.The predation ability of Menochilus sexmaculata is increased with increasing age.The 3rd-instar larvae can prey Megalurothrips usitatus about 625.00 head and the 2nd-instar larvae can prey Megalurothrips usitatus about 454.55head.And when feeding on mixed prey,interspecific interference had a significant effect on prey predation by Menochilus sexmaculata.3.We designed the specific primer of Megalurothrips usitatus and Aphis craccivora by using the sequences of cytochrome oxidase subunit(COⅠ)gene.Then,choose Mus-c1-F6/R7 as the primer of Megalurothrips usitatus,which can amplificate the target insects and the size of DNA is 279 bp.And choose Aca-C1-F2/R6 as the primer of Aphis craccivora which also can amplificate the target insects and the size of DNA is 240 bp.The specific primers only can amplificate the target insects but not other insects in the same habitat.It has a good specificity.It collected 275 heads Menochilus sexmaculata.4.By using the specific primer of Megalurothrips usitatus and Aphis craccivora to detect the predatory of Menochilus sexmaculata in the field.It collected 275 heads Menochilus sexmaculata.The test showed that their are 19.87%of Menochilus sexmaculata can test Megalurothrips usitatus and 31.51%of Menochilus sexmaculata can test Aphis craccivora.In summary,by studying that use of predatory natural enemies Menochilus sexmaculata prey on Megalurothrips usitatus and Aphis craccivora in laboratory.We know that the predation on the two major pests of cowpea under indoor conditions.Meanwhile,evaluating the predatory effects of Menochilus sexmaculata prey on Megalurothrips usitatus and Aphis craccivora in field by using the specific primer.The results of the study will help to clarify the control potential of Menochilus sexmaculata to Megalurothrips usitatus and Aphis craccivora.To provide a basis for control pests in cowpea fields.