Fumigant toxicity of Eucalyptus blakelyi and Melaleuca fulgens essential oils and 1,8-cineole against different development stages of the rice weevil Sitophilus oryzae

Essential oils extracted from Eucalyptus blakelyi (1,8-cineole, 77.5%), Melaleuca fulgens (1,8-cineole, 56.9%) and 1,8-cineole were shown to have fumigant toxicity against different development stages of Sitophilus oryzae. The eggs of S. oryzae were the most tolerant, followed by pupae, larvae and adults in that order. M. fulgens oil, E. blakelyi oil and 1,8-cineole at 100 μl per liter of air gave, respectively, LT₅₀ values of 16.2, 17.4 and 9.1 h for adults, 31.1, 19.3 and 17.5 h for larvae, 55.6, 75.2 and 39.7 h for pupae, and required >7 days for eggs. Only 1,8-cineole (200 μl^-1 air) gave a significant egg kill by 7 days and the LT₉₅ was 134.5 h. 1,8-Cineole could be a useful new fumigant.