Laboratoire d’entomologie, Section défense des végétaux, recherche et développement, Institut National pour l’Etude et Recherche Agronomique de Mulungu, RD Congo
This study consists to evaluate the comparative insecticidal activity of aqueous total extracts of 13 plants used in bean seeds conservation. Currently the yield fall of alimentary foodstuff is not only due to enormous losses which take place before harvest period, but in post-harvest period too. However insecticides, chemical products are inaccessible, expensive and dangerous to be handled by farmers. According to the literature, some insecticide plants, their achievement about the reaction against the devastator insects of foodstuffs in stock, notably: Cedrela sp, Cypress cupressus, Cymbogon citratus, Chenopodium ugandae, Haumaniastrum galeopsis folium, Lantana camara, Lantana trifolia, Mentha aquatica, Rannuculus multifidus, Tagetes minuta, Tephrosia vogelli, Tetradenia riparia and Titonia diverfolia has been evaluated. In fact, the total extracts of Tephrosia vogellii plant have shown a high insecticide activity about 75% of dead insects at a low concentration about 0.0266g/ml. Cedrela sp, Mentha aquatica, Tagetes minuta have shown a low insecticide activity compared with aqueous total extracts of other plants either 0% of dead insects for a low concentration about 0.266mg /ml; but increasing the concentration of the aqueous total extracts of these three plants to 0,28mg/ml, their insecticide activity appeared to 100% of dead insects. The lethal doses or lethal concentrations DL50 and DL90 have been determined for the aqueous total extracts of each plant and the results are found in the table annexed.