Insecticidal and Repellent Activities of Clerodendrum Serratum L. leaf Extract against Rice Weevil, Sitophilus oryzae L.

The rice weevil, (Sitophilus oryzae L. Coleoptera: Curculionidae), is one of the major stored-grain pests of cereals throughout world. During the present study an attempt was made to evaluate the insecticidal and repellent activities of crude methanol extract of Clerodendrum serratum L. against the rice weevil, Sitophilus oryzae L. Insecticidal activity was evaluated using a no-choice test with treated filter paper with wheat grains while repellency evaluated using a choice test with treated filter paper. The crude methanol extract was found to possess moderate insecticidal efficacy against S. oryzae with maximum mortality of 63% at 32 mg/mL (w/v) 7 days after exposure however toxicity depended on both concentration and duration of exposure. The methanol extract was highly repellent against S. oryzae ranging from 23 and 77% at 30 minutes to 2 h after exposure and from 47 to 97% at 4 to 24 h after exposure. The exposure period appeared to be the most important factor affecting the repellency activity of crude extract of C. serratum. Therefore, these leaves extracts may be suggested as admixtures in the integrated management of S. oryzae infestation of cereals during storage.