Insecticidal and repellent activities of eucalyptus oil against lesser grain borer rhyzopertha dominica (fabricius)

Abstract

Lesser grain borer Rhyzopertha dominica (F.) is a destructive insect pest of stored grains. Both larvae and adults of the pest attack whole, sound grain and cause extensive damage. Larvae are internal feeders whereas adults are free living and bore into the commodity and can fly. Fumigation is the most useful and effective method to manage this insect pest. There are several insecticides available in the market to manage this pest but some insecticides have been banned because of environmental pollutions and for some insecticides this insect pest has developed resistance. Therefore efforts are required to find safe, effective and viable alternatives. Natural products are well known to have a range of useful biological properties against insect pests. Recently, there has been considerable interest in essential oils and extracts of medicinal and edible plant and herbs for the development of alternative insecticides and fumigants. This research was initiated to evaluate the fumigation toxicity and repellent action of Eucalyptus globulus Labill essential oil against adults of R. dominica. GC/MS analysis showed the major components of E. globulus essential oil as 1,8-cineole (22.35%), α-pinene (12.58%) limonene (4.01%), aristolene (3.35%), p-cymene (3.25%), trans-verbenol (3.02%), isosativene (2.85%), α-myrcene (2.15%) and terpinen-4-ol (2.10%). Fumigation toxicity and repellent activity showed that as the concentration and exposure time increased the mortality and repellency also increased. Maximum repellency of 62.0% was observed at 0.32μl/cm2 concentration after 36 hours of exposure.