| Xinjiang is one of the most severely affected areas by locust plague in China.In the early outbreak of locust plague,locust nymphs often gather and damage.Early identification of locust nymphs is the difficulty of locust disaster prevention and early warning.For example,it is difficult to accurately classify locust nymphs due to the lack of morphological characteristics of wings and genitalia.DNA barcoding identification technology is not limited by the development stage of insects,and has been used widely for rapid identification of non-adult stages of insects such as Diptera,Lepidoptera and Coleoptera.This study draws the following three conclusions :(1)In this study,the COI gene 1495 bp fragment of mt DNA and ITS gene 655 bp fragment of r DNA of 49 dominant locust adults in Xinjiang were determined,and the local DNA barcoding database of COI and ITS genes was constructed.The intraspecific and interspecific genetic distances of COI and ITS data sets were calculated,and phylogenetic analysis was carried out.The genetic distance of COI and ITS sequences can accurately identify locust species,such as the ratio of average genetic distance between species and average genetic distance within species is up to 25 and 86,respectively.The phylogenetic trees of the two datasets basically conformed to the results of morphological species division at the species level.From the genetic distance and phylogenetic point of view,COI and ITS sequences are suitable for identification of locust species.(2)BLAST,NJ tree,Taxon DNA and ABGD methods were used to identify the COI and ITS sequences of17 nymph samples from Xinjiang.Among the four methods,the highest recognition rate is BLAST and NJ tree.BLAST was faster and simpler,and NJ tree analysis was more effective to reflect the genetic relationship of locusts.The recognition rates of Taxon DNA and ABGD methods were 70.59%–76.47%,and the results were generally consistent.Among the three methods of NJ tree,Taxon DNA and ABGD,only the classification cluster of NJ tree was almost consistent with the classification of adult morphological species.(3)Taking the locusts in Bozhou grassland as the object,this paper compared the control effects of five pesticides(24% beta-cypermethrin WDG,7.5% chlorofluoro imidacloprid SC,0.3% azadirachtin EC,white muscardine fungi WP,green muscardine fungus WP).In terms of persistence,azadirachtin and chlorofluoropyridacloprid showed the best performance,and the control effect could still reach 90% 14 days after application.In terms of speediness,fluochlor pyridacloprid showed the best performance,followed by beta-cypermethrin.In terms of quick effect and persistence,microbial agents(white muscardine fungi and green muscardine fungus)were weaker than other agents.Among the five pesticides,7.5% chlorofluoro imidacloprid SC and 0.3% azadirachtin EC were the best pesticides to control grasshoppers. |
