Abstract
Acetonic plant extracts of Rhazya stricta, Lantana camara, Vernonia cinerea, Withania somnifera and Argemone ochroleuca were tested in the laboratory for their insecticidal and repellent effectiveness to saw-toothed grain beetle, Oryzaephilus surinamensis (L.). Four concentrations of each plant extract, 200, 300,400 and 500 ppm were tested. Larvae and adult beetles were exposed to plant extracts for 6 days. Percentage of mortality was recorded after 2, 4 and 6 days from exposure. The repellent effect of the previous plant extracts was also, studied. All of these plant extracts showed remarkable toxicities. Complete mortality of O. surinamensis was achieved by L camara and R. stricta at the concentration of 500 ppm for both larvae and adult beetles. The rest of plant extracts increased mortality with increasing of concentrations. Of five plant extracts, the effect of L. camara and R. stricta were relatively more pronounced with LC50 values of 200.58 and 230, 25 ppm, respectively, two days from treatment. Corresponding LC50 values after six days exposure for larva, values were 104, 61 and 115, 78. For adult, the LC(50)s values after 2 days were 209.09 and 235.56. After 6 days, LC(50)s were 113.30 and 122.18, respectively. Moreover, R. stricta and L. camara exhibited high repellency 97% and 100% at concentration of 500 ppm against O. surinamensis adults. The application of these extracts may be promising in protecting of stored date and grains against the attack of O. surinamensis specially extracts of L. camara and R. stricta.