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

Abstract

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.