Bioactivity Determination and Control Effect Evaluation of Three Plant Secondary Metabolites against Semiaphis heraclei

[Objective] The paper was to clarify the bioactivity of trans-2-hexenal,oregano oil and thyme oil against Semiaphis heraclei and the synergistic effect of orange peel essential oil and organosilicon on the aphidicidal activity of the three agents.[Method] With S.heraclei,the dominant species of aphids in Lonicera japonica thunb.,as the test insect,the bioactivity and control effect were evaluated by the method of leaf dipping and foliar spraying.[Result] The indoor toxicity of thyme oil was the highest,with the LC_(50) of 1.793 mg/L.Adding additives significantly increased the toxicity of the agents to S.heraclei.Among them,trans-2-hexenal+OSi,oregano oil+OSi and thyme oil+OSi had obvious synergistic effects,with the toxicity coefficients of 1.80,1.48 and 1.45,respectively.Field test showed that the corrected control effect of thyme oil was the highest after con-ventional spraying,and the toxicities of the three agents were higher than that of the control group at 7 d post spraying.Under the condition of 20%reduction of three agents and adding organosilicon,the control effect was increased by about 10% at 1 d post spraying,which was higher than that of the control group at 4 d post spraying,and reached over 98% at 14 d post spraying.[Conclusion] Thyme oil has the highest toxicity and control effect on S.heraclei.Three agents combined with organosilicon have the obvious effect of reducing the quantity and increasing the efficiency,which has the potential for further development.