---

To examine the differences between spinetoram and spinosad in their insecticidal activity and stability on the stored wheat, bioassay tests were carried out for six consecutive months at 20 and 30 ± 1 °C by adults of Rhyzopertha dominica (F.)(Coleoptera: Bostrichidae). Samples were taken after zero, 2, 3, 5, 7, 15, 30, 60, 90 and 180 days of insecticides application. Results of median lethal concentrations (LC50s) determined after three days of treatment indicated that spinosad was significantly more toxic than spinetoram against the adults. Results also revealed that mortality decline of R. dominica was correlated with temperature and the gradual degradation of the two insecticides over time during storage period. The half-life of spinosad and spinetoram on stored wheat were 99.02 and 69.32 days at 20 ± 1 °C, respectively. These were shortened at 30 ± 1 °C to 49.51 and 46.21 days, respectively. However spinosad displayed more bioactivity and stability than spinetoram. It can be concluded that spinosad and spinetoram do not remain persistent and even a slow degradation of these insecticides is likely to occur during wheat storage. Residues of spinosad and spinetoram persist on the wheat grains at levels well below the established tolerance levels.

---

The bioactivity of the aqueous extracts of the leaf of Tetrapleura tetraptera against the wheat storage pest, Rhyzopertha dominica, on stored wheat grains was investigated in laboratory conditions. T. tetraptera leaf extracts were added to 20.0 g of grains at 25.0 mg/l, 50.0 mg/l, and 100.0 mg/l to assess contact toxicity, damage assessment, reproductive performance, and repellency ability. Results showed that the extracts were toxic to the insects. The leaf extracts applied at 100.0 mg/l significantly caused the highest mortality of 94% after 21 days. It also repelled almost 90% of the insects and inhibited adult emergence up to 98%. The 100.0 mg/l of the leaf extract further offered protection of nearly 99% of the wheat grains against insect damage compared to the control. This study revealed that leaf extracts of T. tetraptera can be used to control R. dominica in stored grains efficiently, and its incorporation into traditional storage pest management is strongly recommended in developing countries