Study On Insecticidal Activity,Action Mechanism And Environmental Behavior Of A Novel Aphidicidal Compound OS

Botanical pesticides have become the focus of current pesticide research and application because of their natural advantages of greenness,safety and unique mechanism of action.OS,a novel plant-derived aphidicidal compound,which has been developed based on the insecticidal active steroid skeleton of periplocosides as the leading structure in the early stage of the research group.It has not only novel chemical structure,but also excellent insecticidal activity against aphids,and it has the potential of developing as a green and efficient novel aphidicide.Clarifying the insecticidal effect and environmental behavior of OS will further promote its industrialization.Therefore,the insecticidal activity,environmental behavior and mechanism of action of OS were studied in this research.The main results are as follows:1.The indoor bioassay activity LC₅₀ of Aphis citricola after 48 h of OS treatment was32.68μg/m L by leaf dipping method.The contact and systemic insecticidal activities of OS by drip method and continuous immersion method（hydroponic inoculation method）showed that the LD₅₀/LC₅₀ after 48 h of treatment were 0.084μg/head and 39.14μg/m L,respectively,which suggested obvious effects of contact toxicity and systemic action.2.The field test showed that after 7 days of application,the field control effects of 100and 200μg/m L OS on A.citricola were 81.57%and 87.20%,respectively.After 14 days of application,the field control effect of 200μg/m L OS was as high as 90.31%.The results indicated that OS had a significant insecticidal effect on the A.citricola and long-lasting effect.3.The indoor degradation dynamics of OS in Northeast black soil,Tianjin alkaline soil,Jiangxi laterite and Shaanxi loess under different treatments（aerobic,anaerobic and sterilization conditions）were studied.The results showed that the degradation rates in different soils were:Jiangxi laterite>Northeast black soil>Tianjin alkaline soil>Shaanxi loess,and the degradation half-lives of Jiangxi laterite were 23.10 d,28.88 d and 31.5 d,respectively.While the degradation rates under different treatment conditions:aerobic>anaerobic>sterilization condition.It indicated that OS was mainly related to p H and organic matter content,as well as the population and quantity of soil microorganisms in the process of soil degradation,especially the aerobic soil microorganisms.At the same time,it was found that the degradation process of OS in apple conformed to the first-order kinetic equation,in which the half-life was3.36 d,and the final residues of the normal harvest after the low-dose and high-dose of OS application once and twice respectively were less than 0.01 mg/kg.It showed that OS,as a new environmentally,friendly aphidicidal compound,was easy to degrade and less enriched in soil and apple.4.A total of 304 differentially expressed genes were obtained by high-throughput transcriptome sequencing of A.citricola treated with OS sublethal dose and acetone control treated,including 251 up-regulated genes and 53 down-regulated genes.And nine up-regulated genes involved in mitochondrial energy metabolism were identified,and it was also found that OS treatment could significantly inhibit the activities of complex I and IV by 43.32%and 21.26%,respectively.The above results preliminarily suggested that OS might destroy the respiration of A.citricola by affecting the activity of mitochondrial respiratory electron transport chain complex I and complex IV,which further resulting in poisoning and death.In conclusion,OS is a novel botanical aphidicidal compound with high activity,low residue and unique mechanism of action,which has obvious effects of contact toxicity and systemic action,making it have great prospects for further development.