Attached
in view of worldwide interest and greater public awareness in finding plant products as the most promising
and ecologically safer alternatives for synthetic insecticides in post-harvest protection of stored rice, present
study .yvas undertaken to explore the potential of leaves of Ruta graveolens (Aruda) as a repellent against S.
oryzae infestations. Leaf powder and solvent extracts of R. graveolens were evaluated for their contact and
fumigant repellent properties against seven day old S. oryzae adults. In contact repellency test, weevils (20
Veadhfwere exposed to 1.0 g, 3.0 g, 5.0 g; and 7.0 g of leaf powder mixed with white raw rice grains in a
modified cup bioassay apparatus. Fumigation repellency of leaf powder was tested using same dosages and
the number of weevils in a fumigalion-repeltency chamber. Number of weevils that moved from the bioassav
■ chamfer was recorded one hour after weevil introduction. Leaves of R. graveolens were extracted in hexane.
. ethyl acetate, methanol, distilled water and different concentrations 10. 50. 100% (v/v) were assessed
separately to evaluate repellent activity by means of an area preference bioassay. In all experiments, ten
weevils for each were tested and the number repelled w m recorded 30 minutes after weevil introduction.
Highest contact and fumigant repellent effects were elicited by 7.0 g of leaf powder resulting 96% and 95%,
respectively, whilst lowest dose also produced more than 50%, repellency indicating extremely strong
repellent action of the plant powder. In comparison, aqueous extract exhibited the most potent repellent
•activity.(9!%,) while other extracts were producing over 70% repellent effects on weevils at the concentration
cf 100% (v/v). Overall findings of the. study suggest that both powder and extracts o f R. graveolens leaves
could be used as eco-friendly agents for post-harvest rice protection.
