Insight Into Behavioral Response Of Soil Insect Pests(Hototrichia Oblita And Hototrichia Parallela)to Three Spcecies Of Host Plant Root Exudates

Hototrichia oblita and Hototrichia parallela are the dominant species of agrarian chafer,whose notorious larval development stages are widely distributed across China and cause serious crop damage.In this present study,a handful of trials were conducted to elucidate the behavioral response of aforementioned pest against crops roots.Firstly,the "Y" olfactometer was used to measure the three-instar larvae's behavior response to peanut,soybean and corn roots.Secondly,roots exudates were extracted and analyzed with GC-MS to identify the components of the three crop root exudates,and a field-closure test was conducted for key compounds which exhibited as substantial effect in indoor bioassay.As result,the following key observations were noticed:(1)It was clarified that the larvae of Holotrichia oblita and Hototrichia parallela had significant behavior response to the host plants of peanuts,soybeans,and maize(P < 0.01).(2)It was observed that plant root exudates of the three kinds of hosts had a significant attraction effect on the larvae.The main components of root exudates recorded were 20 or more species for both three crops.In addition to the three common components,namely Glycerol,Dodecanol and Ethylbenzene,there were significant differences among other components.There were 22 secretion components extracted from the root of peanuts.While,the main peanut components obtained with relatively high content included Glycerol,Glyceryl palmitate,Lauric acid,Myristic acid,Palmitic acid,Stearic acid,P-hydroxybenzoic acid and P-hydroxyphenyl octanoic acid,P-toluic acid,etc;The main components of soybean root exudates comprised Glycerol,Methyl succinate,Phthalic acid,Vinyl acrylate,4-methyl-2-oxo-pentanoic acid,3-methyl-4-oxo-pentanoic acid,etc.Twenty main compounds of corn root exudates were also recorded.The key compounds encompass Glycerol,o-xylene,2-butenoic acid,acetic acid,Decane 1,4-epoxyhexane,etc.(3)It was revealed that the concentration effect of the main components of the root exudates of three host plants showed attraction tendencies over the two species.However,some inconsistent responses were also found.A number of compounds tended to react at certain concentrations,whereas some others compounds contrasted the tendency.For example,at a concentration of 100 ?g/m L palmitate,the larvae of Holotrichia oblita and Hototrichia parallela did not respond to this compound,other compounds also responded in similar manner We found that the concentration of the same compound could show an attraction effect on a given larval behavioral test,at the same time exhibiting a contrasting effect on the other test larvae.For example,at the concentration of 160 ?g/m L of Myristic acid,the number of attracted Hototrichia oblita was higher than that of the control insects(P <0.01)whereas the number of control insects of the Hototrichia parallela was very significant at the same concentration more than the number of attractants(P < 0.01).(4)It was revealed that the nine compounds screened in the field-closure test had significant effects on attracting both species.Mycolic acid,Methylsuccinic acid,Acetic acid,2-butenoic acid,and Methyl acetate showed a noticeable attractive effect on the larvae of Holotrichia oblita(P < 0.01).Myristic acid,acetic acid and 2-butenoic acid responded significantly on Holotrichia oblita(P < 0.01)and the attraction effect on the larvae of Hototrichia parallela was significant(P < 0.05).The attraction effect of lauric acid and tetradecane on the larvae of Hototrichia parallela was the same as that of the larvae of Holotrichia oblita(P < 0.05).