Toxic and repellent properties of<i>Xylopia aethiopica</i>(Dunal) A. Richard on<i>Tribolium castaneum</i>Herbst infesting stored millets,<i>Pennisetum glaucum</i>(L.) R. Br.

Abstract

The toxicity and repellency of Xylopia aethiopica seed extract was investigated in the laboratory against Tribolium castaneum Herbst. Concentration and days after treatment (DAT) caused a significant increase in T. castaneum adult mortality with an interaction effect of both on mortality when filter paper was impregnated with X. aethiopica extract. At 0.2 ml/60 cm2 extract, significant mortality was observed at three–seven DAT when compared with one DAT. At 0.4 ml/60cm2, 100% mortality was recorded at the lowest exposure period of one DAT. When 0.2 ml extract was applied to 5 g millet seeds, mortality at five–seven DAT was significantly higher than mortality observed in the control. Although repellency was dose-dependent, the percentage of T. castaneum that were repelled from treated filter paper was not significant. At 0.4 ml/60 cm2, Class II repellency (26.7%) was observed. The results suggest that X. aethiopica can only effectively control T. castaneum populations that have infested millet but do not prevent cross-infestation via repellency.