Abstract:
Prostephanus truncatus Horn (Coleoptera: Bostrichidae) and Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) are two important stored product insect pests found in most storage warehouses. Their activities tend to reduce the viability and the nutritive values of seeds and grains. In this study the bio-efficacy of Zanthoxylum xanthoxyloides and Securidaca longependuncata against P. truncatus and T. castaneum was investigated. The biological effects of methanol extracts of dry roots and leaves of Z. xanthoxyloides and the roots of S. longependuncata at 0.25 g mL-1, 0.5 g mL-1, 1.0 g mL-1 and 2.0 g mL-1 on the two beetle species were determined in the laboratory using dipping, grain treatment, progeny emergence, repellency and grain damage assessment assays. Adult mortality by dipping ranged between 80% and 100% in both insects for the plants extracts. There was no survival recorded at 2.0 g mL-1 of Z. xanthoxyloides roots and leaves and S. longepedunculata roots for both insects in treated grains. Also, no adult emerged in grains treated with 2.0 g mL-1 of the Z. xanthoxyloides roots while the same concentration of S. longepedunculata resulted in only 2% adult emergence for both insects. The methanol extracts of the two plants yielded various levels of repellency against the insects. 2.0 g/mL-1 of the Z. xanthxyloides roots yielded the highest repellency of 90.0 ± 9.5 % and 100 ± 0.0% against P. truncatus and T. castaneum respectively. Grains treated with plant extracts significantly reduced damage caused by P. truncatus and T. castaneum compared with the untreated grains. © JBiopest 370.
