MORTALITY AND REPELLENT ACTIVITY OF CLERODENDRUM VISCOSUM VENT. (VERBENACEAE) AGAINST SITOPHILUS ORYZAE (COLEOPTERA: CURCULIONIDAE)

In continuation of our study we have screened out the root, leaf, and stem of C. viscosum against rice weevil, S. oryzae extracted into ethanol, ethyl acetate, and chloroform. A correlation was found between the insecticidal and repellent activity observed by residual film assay technique and repellency test. It is interesting to note that these plant extracts showed higher to less mortality activity by using 3.93, 1.97, 0.98, 0.49 and 0.25 mg-cm^-2 doses. From the overall assessment suggested that the root extracts showed most potency. Ethanol fraction of root extract exposed 44-84% mortality with 0.39 mg/ml of LC₅₀ value at 72 h of exposure and 95% confidence limit was 0.19 – 0.80. Repellency test carried out ethanol fraction. All the extracts showed 100% repellency (Class V category repellency) in dose no 1 to a dose no 5. The degree of repellency response among the three parts of the test insect was significantly different (P<0.05). Class V category repellency was observed for root and leaf up to dose 0.06 mg-cm^-2 (Dose no 7). Whereas, the lowest dose at which the stem exhibited class V category repellency at 0.12 mg-cm^-2. The root extract showed strong repellent activity than the leaf and stem. The susceptibility of contact toxicity in the intensity of solvents was found ethyl alcohol > ethyl acetate > chloroform fraction. The dose-mortality order of the C. viscosum extracts is root > stem > leaf.