REPELLENCY POTENTIAL OF CERTAIN HERBAL ROOT SAMPLES AGAINST THE GRANARY WEEVIL,SITOPHILUS GRANARIUS L. (COLEOPTERA: CURCULIONIDAE) ADULTS IN STORED WHEAT GRAINS

摘要

Repellency of Glycyrrhiza glabra,Zingiber officinale,Raphanus sativus var.niger and Daucus carota var.atrorubens along with permethrin dust against Sitophilus granarius was evaluated in the laboratory at 27 ± 1 °C and 65 ± 5 % RH.The herbals were applied as dusts,methanolic,ethanolic and aqueous extracts at the rate of 5.0,10.0 and 20.0 x 104 ppm per 40 g of wheat grains,while the permethrin dust was applied at 0.055 x 104 ppm.Percentage repellency was recorded at 1,6,12 and 24 hours after treatment (HAT).All the herbals were found to have a repellent effect against Sitophilus granarius at all three concentrations.The highest (90.18 ± 2.83) repellency among the herbal dusts was exhibited by 20.0 x 104 ppm of Glycyrrhiza glabra within 24 HAT.Methanolic root extracts were found to be more effective than the other formulations,causing total repellency against the weevils at 20.0 x 104 ppm of all the herbals,while the activities of the aqueous extracts were the least repellent (45.49 ± 7.49 to 64.30 ± 1.50 %) after 24 hours of exposure.The repellent activities of the herbals decreased with increasing exposure periods for dusts and aqueous extracts and increased with increasing duration for methanolic and ethanolic root extracts.The results showed that the herbals were good repellent against Sitophilus granarius and could serve as stored wheat grain protectants against wheat granary weevil infestation.