Essential oils as fumigant against rice weevils, Sitophilus oryzae (Linnaeus)

Abstract

The fumigant activity of twenty-five essential oils was evaluated on an important stored-product insect pest Sitophilus oryae Linn. The essential oils from Cinnamomum porrectum (Roxb) Kosterm (Thep ta-ro) exhibited the highest fumigant toxicity against adults of S. oryzae after 24 h exposure, followed by those from Mentha arvensis Linn (Japanese mint) and Zingiber cassumunar Roxb (plai) with LC[subscript50] 79, 138 and 260 L/L air, respectively. The main constituents of each essential oil were analyzed by spectroscopic techniques and then tested in fumigation bioassay. Safrole, the major component of the essential oil from C. porrectum, exhibited the most potent fumigant (LC[subscript50] = 57.9 L.LO air) at the concentration of 100 L/L air after 24 h exposure. Additionally, the residue of safrole could not significantly be detected on the fumigated rice. The major component-fumigant activity relationship study revealed that menthol (LC[subscript50] = 95.4 L.L air) was an active component of the essential oil from M. arvensis, while terpinen-4-o1 (LC[subscript50] = 165.5 L.L air), one of the major constituents of the essential oil from Z. cassumunar, was an active component. Thus, the essential oils from all three plant sources and their major constituents may be developed as a potent fumigant for storage grains.