Extraction of Pyrethrins from Chrysanthemum cinerariifolium petals, its application as a Bioinsecticide and study of its effects on Rice Weevil Sitophilus oryzae

Abstract

The Rice Weevil Sitophilus oryzae is one of the most destructive primary storage product pests worldwide and is known for attacking stored grains such as wheat, corn, oats, and rice. A wide variety of agricultural chemicals are being used as pesticides but sole reliance on these chemical-based insect-killers is not safe and sufficient. These are now being replaced by organic or bio-pesticides which are biodegradable, have less toxicity to humans, and provide slow but effective insect repulsion. Thus, a pyrethrin-based bio-insecticide emulsion was prepared by solvent extraction method using locally available Chrysanthemum cinerariifolium flower petals. Its biological activity against the rice weevil Sitophilus oryzae was then observed. HPLC analyses were done to validate the presence of pyrethrin in the extract. The bio-insecticide was sprayed on the rice weevils in concentrations of 20%, 40% and 60%. It was observed that pyrethrin extract in solvent mixture i.e. petroleum ether, acetone and ethanol (1:1:1) proved much more effective than the extract containing petroleum ether as the sole solvent. Telsta® (Clothanidin), a synthetic chemical pesticide was set as a control group and was observed to be more potent as it killed 95% of the rice weevils on direct contact. The death percentage from petroleum ether method was 90%, at concentrations 20%,40% and 60%, while in solvent mixture method,death percentage was 90% at conc. 20% and 100% at conc. 40% and 60% respectively after 48 hours for both methods.It was concluded that natural biopesticides are almost equally potent against rice weevils as the chemical pesticides, but they require longer exposure time (24-48h) for their effectiveness.