Screening of Allamanda cathartica L. extracts against stored product pests, Tribolium castaneum (Herbst), Sitophilus oryzae (L.) and Callosobruchus chinensis (L.)
Umme Habiba Mustary, Ainun Nahar, Shahina Begum Rekha, Ariful Hasan and Nurul Islam
Petroleum ether (Pet. ether), CHCl3 and CH3OHextract of leaves and stem-bark of the medicinal plant Allamanda cathartica L. were tested for dose-mortality and repellent activity against three stored product pests,Tribolium castaneum (Herbst),Sitophilus oryzae (L.) and Callosobruchus chinensis (L.) adults. Against T. castaneumthe leafextracts of Pet. ether, CHCl3 and CH3OHgave LD50 values 3.433, 2.347, 2.091, 1.879, 1.533and 1.309mg/cm2;2.179, 1.898, 1.532, 1.300, 1.136and1.055mg/cm2; and 2.598, 2.097, 1.892, 1.645, 1.476and 1.357mg/cm2 respectively. For S. oryzae, the same extracts gave LD50 values 1.532, 1.341, 1.120, 1.010, 0.921and 0.921mg/cm2; 1.860, 1.669, 1.444, 1.257, 1.240and 1.114mg/cm2; and 2.758, 2.610, 2.289, 2.250, 2.040 and 1.947mg/cm2; andforC. chinensis the LD50 values for the same were 2.439, 1.536, 1.105, 0.810, 0.713and 0.685mg/cm2 ; 2.439, 1.536, 1.534, 1.314, 1.095and 1.069mg/cm2; and 3.017, 2.742, 2.570, 2.380, 2.164and 1.985mg/cm2 respectively after 6, 12, 18, 24, 30and 36h of exposure. The Pet. ether and CHCl3 extracts of the stem-bark of the test plant gave LD50 values against T. castaneum were 3.402, 3.095, 3.066, 2.077, 1.699 and 1.419mg/cm2; and 3.283, 3.196, 3.047, 2.220, 2.056 and 1.756mg/cm2respectively; against S. oryzae, the LD50 values were 3.140, 2.528, 2.147, 1.745, 1.398 and 1.182mg/cm2; and3.408, 2.477, 2.284, 2.092, 1.860 and 1.636mg/cm2; and against C. chinensis, the LD50 values were 3.433, 2.347, 2.091, 1.879, 1.533and 1.309mg/cm2; and 3.711, 2.492, 2.327, 2.050, 1.866 and 1.674mg/cm2 respectively after 6, 12, 18, 24, 30 and 36h of exposure. However, the CH3OH extract of stem-bark didn’t offer mortality to the test beetles. All the extracts were subjected to repellent activity tests against the same three test agents, and no repellent activity was detected against any of the test agents.