FAROUK BOUROGÂA, KLAUS BECKER, STEFAN VIDAL
Georg-August-Universität Göttingen, Dept. of Crop Science, Germany
University of Hohenheim, Dept. of Animal Production in the Tropics and Subtropics, Germany
The physic nut tree, Jatropha curcas (Euphorbiaceae) is an oil seed plant widely distributed in tropical and subtropical regions. Traditionally, this tree is grown as a natural hedge and used in ethno medicine. Several phytochemicals from this plant are known for their toxic properties against herbivorous insects. In fact, the toxicity of the seed oil is attributed to several phytochemicals including saponins, lectin (curcin), phytates, protease inhibitors, and curcalonic acid; but the main toxic action has been assigned to the Phorbol Esters, a diterpenoid fraction contained in the seed oil. In this study, we tested the insecticidal effects of two different extracts: the Phorbol Ester Enriched Fraction (PEEF) and the essential oil extracted from the seeds (JP-32). The PEEF was tested on the cotton bollworm Helicoverpa armigera (Lepidoptera) by mixing the artificial medium with different concentrations. This fraction was also tested on the cabbage root fly Delia radicum (Diptera) by soil drench of cabbage plants infested with the eggs of this pest. Also, different concentrations of the essential oil of the seeds (JP-32) were tested on the black bean aphid Aphis fabae (Hemiptera) under greenhouse conditions. The results evidenced the insecticidal effect of PEEF on H. armigera and show a significant effect at 10% of PEEF on the survival rate of D. radicum compared to the control plants. The essential oil of the seeds shows a concentration-dependent toxicity on A. fabae after 5 days. These bioassays allow insight into the biocidal effects of phorbol esters and the opportunities provided by Jatropha curcas as an additional measure in pest management.
Keywords: Aphis fabae, Delia radiucm, Helicoverpa armigera, Jatropha curcas, mortality, phorbol esters