Laboratory Study of Repellent Property of Bhut Jolokia Chilli against Sitophilus oryzae (Coleoptera: Curculionidae) in Stored Wheat1

Abstract

This study investigated the repellent property of ‘Bhut Jolokia’ chilli pepper, a Capsicum chinense Jacquin cultivar, against the rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), in stored wheat, Triticum aestivum L., in laboratory assays using a modified cup bioassay apparatus. Contact and fumigation repellency assays were conducted with the Bhut Jolokia chilli dry powder at concentrations of 3 and 5% (w/w) of the total weight of grain and the Bhut Jolokia chilli ethanol extract at volumes of 3 and 5 ml. In the contact repellency test, the number (mean ± SE) of test insects repelled (7.90 ± 0.23) increased with increasing concentration (5%) and time interval (24 h), whereas in the fumigation repellency test, the mean number of repelled insects increased (8.2 ± 0.2) with increasing volume (5 ml) and decreased (3.80 ± 0.13) with increasing time interval (60 min). Gas chromatography–mass spectrometry (GC-MS) analysis identified that the active compounds present in the Bhut Jolokia chilli ethanol extract were the capsaicinoids capsaicin (21.50%) and dihydrocapsaicin (4.44%) and the noncapsaicinoids n-hexadecanoic acid (29.34%), n-pentadecylacetamide (12.92%), and others. Our findings provide a preliminary assessment of the repellent property of Bhut Jolokia chilli against S. oryzae in stored wheat under laboratory conditions and serve as an impetus for continued research.