Screening of Allamanda cathartica L. extracts against stored product pests, Tribolium castaneum (Herbst), Sitophilus oryzae (L.) and Callosobruchus chinensis (L.)

Petroleum ether (Pet. ether), CHCl3 and CH3OH extract 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. castaneum the leaf extracts of Pet. ether, CHCl3 and CH3OH gave LD50 values 3.433, 2.347, 2.091, 1.879, 1.533 and 1.309mg/cm2; 2.179, 1.898, 1.532, 1.300, 1.136 and 1.055mg/cm2; and 2.598, 2.097, 1.892, 1.645, 1.476 and 1.357mg/cm2 respectively. For S. oryzae, the same extracts gave LD50 values 1.532, 1.341, 1.120, 1.010, 0.921 and 0.921mg/cm2; 1.860, 1.669, 1.444, 1.257, 1.240 and 1.114mg/cm2; and 2.758, 2.610, 2.289, 2.250, 2.040 and 1.947 mg/cm2; and for C. chinensis the LD50 values for the same were 2.439, 1.536, 1.105, 0.810, 0.713 and 0.685mg/cm2 ; 2.439, 1.536, 1.534, 1.314, 1.095 and 1.069mg/cm2; and 3.017, 2.742, 2.570, 2.380, 2.164 and 1.985mg/cm2 respectively after 6, 12, 18, 24, 30 and 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/cm2 respectively; against S. oryzae, the LD50 values were 3.140, 2.528, 2.147, 1.745, 1.398 and 1.182mg/cm2; and 3.408, 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, 1.533 and 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.