African Journal of Biotechnology Vol. 6 (4), pp. 379-383, 19 February 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Ethanolic extract of melgota (Macaranga postulata) for repellency, insecticidal activity against rice weevil (Sitophilus oryzae)

Syed Shayfur Rahman¹, Md. Mizanur Rahman^1*, Mohammad Mizanur Rahman Khan¹, Shameem Ara Begum¹, Balaram Roy² and S. M. Fakruddin Shahed¹

¹Department of Chemistry, Shahjalal University of Science and Technology, Sylhet, Bangladesh.

²Department of Agricultural Chemistry & Biochemistry, H. M. D. Science & Technology University, Dinazpur, Bangladesh.

*Corresponding author. E-mail: mizan_sust@yahoo.com.  Tel: 880-821-713491(ext. 151).

Accepted 27 November, 2006

Ethanolic extract of Melgota is used for repellency, insecticidal activity against rice weevil (Sitophilus oryzae) with emphasis on chemical investigation. Fruits of Melgota (Macaranga postulata) were extracted on different solvents as in ethanol, acetone, petroleum ether, distilled water and the extracts were concentrated and dried. The ethanol extracts of Melgota (M. postulata) of different concentrations were investigated for their repellency and insecticidal activity against S. oryzae. Average mortality percentage indicated that the extracts caused significant mortality and repellency on the target insects and bioassays indicated that the toxic and repellent effect was proportional to the concentration and higher concentration has stronger effect. Observed mortality percentage increased with increase in time intervals after treatment. Mortality percentage at 0.25,   0.50, 0.75, 1.00, and 1.50 h after treatment (HAT) indicated that 4% solution showed the highest mortality (34.0%) in S. oryzae at 1.50 HAT compared to pediculus humanus. Mortality percentage showed parallel response to the level of concentration at different time intervals after treatment. 1% fruit extract of Melgota (M. postulata) showed the lowest repellency 9.84 % in case of rice weevil. On other side, 2% showed 12.76% and 4% showed 22.43% respectively. TLC of crude ethanol extract of Melgota (M. postulata) showed six distinct compounds at uv-visible light.

Key words: Macaranga postulata, Sitophilus oryzae, mortality, repellency.