Fumigant effect of essential oils against pulse beetle (Callosobruchus chinensis L.) and rice weevil (Sitophilus oryzae L.) in stored products

Abstract

Objectives: To develop a method to replace the usage of synthetic fumigants in stored product pest management. Methodology: For this purpose, we employed four plant based essential oils namely, Lantana camara (Lantana) oil, Citronella nardus (Citronella) oil, Cinnamomum zeylanicum (Cinnamon) oil and Trachyspermmum copicum (Ajwain) oil and evaluated against pulse bee- tle, Callosobruchus chinensis L., and rice weevil, Sitophilus oryzae L., for their fumigant toxicity and the weight loss caused by them. The oils of Lantana and Citronella were extracted from leaves, Cinnamon and Ajwain from barks and seeds respectively. Findings: Among the essential oils tested for fumigant tox- icity, C. zeylanicum performed better with Lethal Concentration (LC50) of 23.16 and 21.91µl in minimal period of exposure i.e. at 12 h of treatment and found effective against adults of test insects viz., C. chinensis, and S. oryzae respec- tively. During the maximum period of exposure i.e. at 72 h. the fumigation efficacy of T. copicum was noticed to be the highest (3.43 µl) against adults of C. chinensis whereas C. zeylanicum was found better against S. oryzae (6.19 µl). The minimum loss of pulse grains was observed in C. zeylanicum treated at 60 % of 24 h LC50 , with 7.41 % weight loss. The minimum weight loss was noticed in C. zeylanicum about 60 % of 24 h LC50 with 9.68 per cent against S. oryzae. The fumigant toxicity bioassay revealed that as the exposure period increases, mortality of test insects also found increased i.e. exposure period directly proportional to mortality of insects. Keywords: