Study On The Insecticidal Activity Of Two Kinds Of Plant Essential Oils Against Tribolium Castaneum Herbst

Tribolium castaneum Herbst is one of the important stored grain pests.The long-term use of chemical fumigants is not conducive to the green development of grain storage.The development of low-toxic,safe and efficient botanical insecticides has important research significance and value.In this paper,the fumigation effects of 39 kinds of plant essential oils on T.castaneum were preliminarily screened.The insecticidal activity of dill oil and Rabdosia excisa oil on T.castaneum was studied,and the simulated storehouse control experiment was carried out.The biochemical mechanism of the insecticidal effects on T.castaneum was explored,and the chemical components of dill oil and R.excisa oil were analyzed.Finally,the fumigation activity of single dose and compound chemical components on T.castaneum was studied.The main research results are as follows:1.The fumigation effects of 39 kinds of plant essential oils from 35 genera of 23 families were preliminarily screened by triangular bottle closed fumigation method.The results showed that the corrected mortality rate of the 7 kinds of plant essential oils reached 100%at the concentration of 150μL/L after 24 h fumigation,including R.excisa oil,lemon verbena oil,Strychnos nux-vomica oil,dill oil,schefflera oil,citrus oil and camphor oil.The corrected mortality rates were 100%,67.78%,50.00%,40.00%,38.89%,26.67%and 23.33%at the concentration of 15μL/L after 72 h fumigation.2.The dill oil and R.excisa oil were selected as 2 kinds of high-efficiency plant essential oils to determine the fumigation,contact and repellent activities at different time and concentrations.The results showed that dill oil and R.excisa oil had better fumigation effects on T.castaneum.The median lethal concentrations(LC₅₀)of dill oil and R.excisa oil were5.76μL/L and 8.38μL/L after 72 h fumigation,respectively.Dill oil and R.excisa oil also showed better contact effects on T.castaneum.The corrected mortality rate of dill oil and R.excisa oil reached 100.00%at 0.885μL/cm² and 2.212μL/cm²after 72 h contact,respectively.At the same time,the 2 kinds of plant essential oils had strong repellent effects.At a concentration of 78.63 n L/cm²,the repellent rates were 93.92%and 67.42%after 72 h treatment,and the repellent grades were V and IV,respectively.3.In the wheat simulated storehouse test,the fumigation concentration was increased to verify the control effects of dill oil and R.excisa oil on T.castaneum at different time and concentrations.The results showed that dill oil and R.excisa oil had good control effects on T.castaneum,and the poisoning effects were upper>middle>lower in the wheat storehouse.Among them,the corrected mortality rate of the upper layer reached 100%on T.castaneum at 0.1 m L/L,0.2 m L/L,0.3 m L/L,0.4 m L/L and 0.5 m L/L after 28 d of dill oil treatment.The corrected mortality rates of the middle layer were 62.00%,73.33%,97.33%,100%and100%,and the corrected mortality rates of the lower layer were 0%,14.00%,30.67%,74.67%and 100%,respectively.Besides,the corrected mortality rates of the upper and middle layers reached 100%at the concentrations of 0.2 m L/L,0.4 m L/L,0.6 m L/L,0.8 m L/L and 1.0m L/L after 28 d of R.excisa oil treatment,and the corrected mortality rates of the lower layer were 38.00%,51.33%,64.67%,100%and 100%,respectively.4.The LC₅₀ of dill oil and R.excisa oil was used as the standard concentrations to treatT.castaneum at 72 h fumigation time,and it was that to explore effect of enzyme activity in T.castaneum.The results showed that dill oil and R.excisa oil significantly inhibited the activities of ACh E and Car E in T.castaneum within 72 h.Among them,the 2 kinds of plant essential oils had the highest inhibition rates of ACh E activity were 71.13%and 58.62%in vivo at 60 h and 12 h,respectively.The highest inhibition rates of Car E activity were 67.16%and 63.55%in vivo at 36 h and 48 h,respectively.The activity of GST showed significant activation in vivo at 12 h,and showed significant inhibition after 24 h.The highest inhibition rates of GST activity were 60.35%and 42.73%in vivo at 24 h and 72 h,respectively.5.The chemical constituents of dill oil and R.excisa oil were analyzed by GC-MS.The results showed that there were 19 compounds in dill oil,accounting for 98.17%of the peak area.The main components were D-carvone（39.65%）,Limonene（35.07%）and Apiol（15.29%）.Among them,the relative content of D-carvone was the highest.There were28 compounds in R.excisa oil,accounting for 78.53%of the peak area.The main components were o-Cymene（34.17%）,3-Carene（10.18%）,Linalool（6.28%）and alpha-Phellandrene（5.94%）.Among them,the relative content of o-Cymene was the highest.6.According to the results of GC-MS analysis,2 kinds of single doses of D-carvone and o-Cymene were selected as the test agents,and the adults of T.castaneum were used as the test objects to determine the fumigation activity at different time and concentrations.The results showed that D-carvone and o-Cymene had good insecticidal effects,and the LC₅₀ of the 2 kinds of single doses were 4.85μL/L and 16.89μL/L after 72 h fumigation,respectively.The interaction level（SR）was analyzed at different fumigation time by interaction determination method for different proportions of 2 kinds of single agents.The results showed that the 9 kinds of compound combinations had synergistic effects.Among them,the ratio of D-carvone to o-Cymene was 8:2,and the synergistic effect was the best after 72h fumigation,which the SR was 3.50.To sum up,dill oil and R.excisa oil had significant insecticidal effects on T.castaneum.The main chemical components of D-carvone and o-Cymene had significant poisoning effects on T.castaneum after fumigation,and the combinations of D-carvone and o-Cymene had synergistic effects.