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

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.