EFFECT OF IVY (HEDERA-HELIX) LEAF EXTRACT AGAINST APPLE SCAB AND MILDEW

Extracts of ivy (Hedera helix L.) leaves inhibit the conidial germination of of Venturia inaequalis and show a preventive activity against scab and powdery mildew on apple seedlings under controlled conditions. The triterpene-saponins hederacosid C and alpha-hederin are responsible for the fungicidal activity of the leaf extract; alpha-hederin is formed after wounding of the tissue from hederacosid C by splitting off one sugar chain. Solutions of the synthetic substances inhibit conidial germination and the development of scab on the leaves. The saponines remain active in ground dried leaves stored at 0-degrees-C for more than 18 months. Extracts stored at 0-degrees-C remain active for at least one week. The activity is persistent on leaves of apple seedlings under controlled conditions up till 4 d after the treatment. Solvent and method of extraction have no influence on the fungicidal properties. 1% cold water extracts showed an efficacy of more than 90% against scab in most trials; it is planned to test the ivy leaf extracts at this dilution in the field. A biotest using conidia of Trichoderma koningii has heen developed for the fast test of saponine-activity.