Study On Population Dynamics And Mechanisms Of Peanut Thrips In Maize-Peanut Intercropping Landscape

Peanut(Arachis hypogaea)is one of the important oil crops in China.Qingdao is a traditional dominant peanut producing area in China,where the population of thrips is increasing more seriously than before.However,the study on identification and resistance to insecticides of peanut thrips is still limited.The effect of chemical control is not ideal and causes great pollution to the environment.Maize-peanut intercropping,as a new planting pattern proposed by the state for the balanced development of grain and oil in recent years,has been listed as a major reserve technology in the 14th Five-Year Plan.However,whether intercropping pattern has beneficial effect on peanut thrips population or not is still unknown.Based on this,field investigation,insect classification,indoor natural enemy predation function research,and other techniques were used to study the occurrence of thrips,their natural enemies and predation function in peanut field.The results are as follows:1.The species and population dynamics of thrips in Qingdao Laixi peanut field were clarified.With field investigation,laboratory morphology,and molecular identification,the main species of thrips in Qingdao Laixi peanut field are Frankliniella intonsa,Thrips tabaci,Haplothrips aculeatus,and Aeolothrips fasciatus.The percentage in intercropping and peanut monoculture were 66.13%,21.21%,11.68%,0.98% and 65.70%,21.48%,11.77%,1.45% respectively.The population dynamics of thrips were similar between intercropping and peanut monoculture,which mainly occurred from mid-June to late August,among which June 28 and July 28 were the peak periods.The dominant species of thrips in different period were different.Thrips tabaci and Aeolothrips fasciatus occurred in earlier stage,mainly from mid-June to early July,among which the peak period occurred around June 28.Haplothrips aculeatus mainly occurred from mid-June to late July,and the peak period occurred around July 10.Frankliniella intonsa mainly occurred from late June to late August,of which June 28 and July 28 were the peak periods.2.The influence of maize-peanut intercropping landscape on peanut thrips was preliminarily clarified.Overall,intercropping significantly reduced the number of thrips(P<0.01),especially reduced the number of July 28 and August 10(P<0.01,P<0.05).According to the species,intercropping significantly reduced the number of Frankliniella intonsa(July 28 and August10)and Thrips tabaci(June 28),reduced the number of Haplothrips aculeatus(July10)(P<0.01;P<0.05;P>0.05).3.The indoor predation function of the main predatory natural enemy of Orius sauteri on thrips was clarified.The genome of the intestinal contents of Orius sauteri was extracted and PCR amplified with thrips primer.The result showed that 12.75% of the samples appeared target bands,suggested that Orius sauteri did have predation function on thrips.4.Analysis on the mechanism of thrips population reduction in Maize-peanut intercropping landscape from the natural enemy control.By using niche and population dynamics,combined with indoor predation function analysis,we found Hylyphantes graminicola and Frankliniella intonsa;Aeolothrips fasciatus,Harmonia axyridis and Thrips tabaci;Orius sauteri and Haplothrips aculeatus had large temporal,spatial and time-space two-dimensional niche similarity ratio index.In addition,the dynamics of natural enemy’s population were similar to thrip’s.Besides,the intercropping reduced the number of Frankliniella intonsa,Thrips tabaci,and Haplothrips aculeatus(P<0.01;P<0.05;P>0.05).At the same time,the number of Hylyphantes graminicola,Harmonia axyridis and Orius sauteri were increased significantly(P<0.05;P<0.05;P<0.05).