DOI: 10.36347/sajb.2018.v06i03.002

Pages: 247-251

A thorough screening of the indigenous plant Tabernaemontana divaricata (L.) leaf and stem bark were extracted separately in petroleum ether (Pet-ether), chloroform (CHCl3) and methanol (CH3OH) has been done for the detection of bioactive compounds. The extracts of leaf and stem bark were subjected to repellency and dose mortality assay against the stored product pest Callosobruchus chinensis L. adults. The Pet-ether extract of leaf showed moderate repellency at 1% level of significance (p < 0.01), while the CH3OH extract of leaf and the Pet-ether, CHCl3 and CH3OH extract of stem bark gave mild repellency at 5% level of significance (p < 0.05), but the CHCl3 extract of leaf did not show any repellency. According to the intensity of activity the results could be arranged in a descending order: Pet-ether > CH3OH > CHCl3 for the leaf extracts and CH3OH > CHCl3 > Pet-ether for the stem bark extracts respectively. The Pet-ether extract of both the leaf and stem bark were tested against the adult beetles of C. chinensis L. through dose mortality assay, and LD50 values were established as 3.289, 2.796, 2.512, 2.053, 1.846 and 1.572 mg/cm2 and 4.219, 3.604, 3.579, 3.041, 2.419 and 1.953 mg/cm2 for leaf and stem bark respectively at 6h, 12h, 18h, 24h, 36h and 48h of exposure. However, the CH3OH extract gave the LD50 values 6.689, 9.136E-05, 6.336, 4.591, 2.569 and 1.813 mg/cm2 and 4.854, 5.272, 4.066, 3.17, 2.667 and 2.431 mg/cm2 for both the leaf and stem bark extracts respectively at the same exposure time. The CHCl3 extracts of both the leaf and stem bark did not show any mortality to the test organism.