Abstract: Cestrum parqui is a shrub used in Tunisia as ornamental plant. The insecticidal activity of the leaves of this plant was demonstrated the first time on desert locust (Schistocerca gregaria); this toxicity comes from the saponic fraction of the plant. The aim of present research is to explore the pesticidal toxicity of Cestrum parqui saponins on some plant pest organisms like insects, fungus, mollusks and nematodes. The results show that saponins are toxic to some other insects like Spodoptera littoralis and Tribolium confusum, this toxicity is probably due to cytotoxic activity of Cestum parqui saponins, this was demonstrated histologically on the fat body and the gut of Schistocerca gregaria and Spodoptera littoralis. This toxicity can be also the result of interference with ecdysone metabolism by the obstruction with dietary cholesterol; this hypothesis was proved biologically on Tribolium confusum. The molluscicidal activity of Cestrum parqui saponins was observed on Theba pisana snails. Our investigation on the mode of action of these substances shows that saponins interfere with the water retention mechanisms witch causes mortality by dehydratation. Saponins are especially toxic for the eggs of Meloidogyne incognita nematode. This was illustrated in vitro experiments and confirmed in vivo assays on tomato plants infected with the nematode pest. Cestrum parqui saponins are, on the other hand, totally ineffective against phytopathogenic fungi (Fusarium solani, Botrytis cinerea). This is probably due to the secretion of detoxifying enzymes. Cestrum parqui represents a high potential for isolating natural pesticide molecules. More studies are necessary to purify and identify pesticidal products from Cestrum parqui saponic crude extract and to confirm physiological action of these compounds.
Chaieb Ikbal, Ben Halima-Kamel Monia, Trabelsi Mounir, Hlawa Wassila, Raouani Najet, Ben Ahmed Dorsaf, Daami Mejda and Ben Hamouda Mohamed Habib, 2007. Pesticidal Potentialities of Cestrum parqui Saponins. International Journal of Agricultural Research, 2: 275-281.