Studies On Bio-Activities Of Plant Extract Against Cucumber Powdery Mildew And Their Active Substances' Extraction And Purification

Bio-activity of different tissues extracts from 30 plants in Shanghai against Sphaerotheca fuligenea was tested. The results showed that three extracts from leaf of Dalbergia hupeana Hance., leaf of Sophora japonica L. and whole plant of Euphorbia humifusa Willd had a better preventive effect than the other extracts against cucumber powdery mildew on leaf disks.Bioassay of the extract from leaf of D. hupeana showed that at the concentration of 167 mg/ml, it had 67.86% preventive effect and 89.81% curative effect against cucumber powdery mildew on potted plants in the cultural room. The effect could maintain upwards of 42.59% for 12 days after the treatment. The extract of D. hupeana was not sensitive to the change of temperature and sunlight through stability testing. The bio-activity wasn't easy to be weakened under UV irradiation. It was acid-resistant but not alkali-resistant. The preventive effect in the field testing was not good as the result of 18.31%.Bioassay of the extract from leaf of S. japonica showed that at the concentration of 500 mg/ml, it had 76.81% preventive effect and 76.86% curative effect with the same testing. The effect could maintain upwards of 46.29% for 12 days after the treatment. The bio-activity of heated extract would be enhanced in the stability testing. It was not sensitive to...