Studies On Insecticidal Activities Of Extracts From Medicago.sativa(L.) Against H.armigera

Bioactive substance from the seed of Medicago.sativa.L was extracted by different methods. Insecticidal activities of crude extracts and fractions against H.armigera were tested, and its effects on activities of several enzymes from the insect were evaluated. The result was as follows:1.The results indicated that extraction with methyl alcohol was the most effective extraction method ,the extract rate was about 4.63%, but extraction with ethanol relatively low for the main solvent, it is 2.65%.2.A antifeeding experiments showed that two extracts possessed antifeeding activities against the insect. AFCso value of ethanol extracts was 20.66mg/ml at 24 hours after treatment in no-choice tests, but AFCso value of methyl alcohol extract was 25.11 mg/ml.Two extract had a certain ovipositor deterrence activity against H.armigera larvae, but that of those treated with extract of Medicago.sativa.from the seeds had not significant difference between the treated and control.Ethanol extracts and methyl alcohol extracts demonstrated significant inhibition on growth of the cotton bollworm and larval weigh, The inhibition rate that the larvae was treated with ethanol extracts were up to 85.21% after 4 days, methyl alcohol extracts were 57. 04%.When comparing the treatment with the control, Larva development was slow, the weight gained was reduced, larvae died .mortality was higher. At the concentration S.Omg/ml that of the larvae, the development duration of larvae treated with ethanol extracts prolonged 7 days than control, methyl alcohol extracts have lengthened 5 days.Two extracts had deleterious effects on pupation and emergence, caused deformity of pupa and adult, pupa size smaller than control, pupa ascend to heaven. At the concentration 8.0mg/ml, the rate of deformed pupa of methyl alcohol extract was up to 16. 4%, the rate of adults with deformed wing was 18. 9%, the deformity pupa rate of ethanol extracts was 15.6%, the deformity wing rate was 16. 7%.3.The results on the activities of several enzymes showed that the extracts had obvious inhibition effect to the protein in the body of pest; The glutathion-S-transferase(GsT) activities were obviously higher than control; The carboxylesterase(CarE) activities were induced; But the acetylcholinesterase(AchE) activities had not difference between the treated pest and control.