Toxicity Experiments of the Saponic Extract of Cestrum Parqui ( Solanaceae ) on Some Insect Spices

摘要

The goal of present study is to undertake various experiments to explore this entomotoxic activity of this extract on various harmful insects in order to determine the best mode of application of these natural biopesticides. Several insects were tested in these experiments: Two phytophagous insects: desert locust ( Schistocerca gregaria ) and the cotton noctuid ( Spodoptera littoralis ), a stored products devastating insect ( Tribolium confusum ) and a health harmful hematophagous insect ( Culex pipiens ). Several biological toxicity assays were elaborate according to the species and the stage used. Experiments utilizing injection, grafting, forced ingestions, experiments of contact toxicity or toxicity by incorporation to the food substrate were employed. All these experiments enabled us to conclude that the application by contact of the CSE is generally ineffective because of the impossibility of passage of saponins (hydrophilic molecules) through the cuticle of the insect. The saponic extract must be introduced by the insect to express a toxicity from where the idea to design toxic soft foods based on extract saponic of Cestrum .