EVALUATION OF EUCALYPTUS GLOBULUS EXTRACTS FOR THE CONTROL OF RICE WEEVIL, SITOPHILUS ORYZAE

Botanical materials derived from flowers, leaves and branches of Eucalyptus globulus were extracted consecutively through five solvents varied in their polarities namely; hexane, petroleum ether 40-60°C, chloroform, ethanol and acetonitrile to study their biocide activity against Sitophilus oryzae. Preliminary studies indicated that 20 mg/ml ethanol flowers and leaves had significant deterrent effects on insect grain damage as well as increased adult insect mortality. Also, there are significant differences on adult emerged between all chloroform extracts and control. Activity of 20 mg/ml plant extracts against adult and feeding deterrence to S. oryzae suggest promising extracts. According to correlation coefficient values of promising extracts a significant succession linear relationships were found between tested concentrations and antifeedant effect with chloroform leaf and branch extracts, and percentage adult mortality with chloroform branch and ethanol flower extracts. Significant reversal linear relationship was recorded between tested concentrations and percentage of grain damage with ethanol leaves extract. According to phytochemical investigation, chloroform flowers, leaves and branches extracts contained sterols and/or triterpens, cardic, alkaloids and flavonoids. Whereas ethanol flowers and leaves extracts contained pyrogallol tannins, phenolic glycosides, saponine glycosides and alkaloids. On the other hand, catecol tannins was found in chloroform leaves and branches extracts only. Laboratory studies showed that the promising extracts have potential as stored-product insect, S. oryzae control agent, because it significantly deters feeding as well as emergence to F1 adult of S. oryzae. And also have slight toxic action against insect. It is suggested that these biologically active natural products may serve as suitable prototypes for the development of commercial insecticides.