Insecticidal activities of aromatic plant extracts and essential oils against Sitophilus oryzae and Callosobruchus chinensis

Methanol extracts from 30 aromatic medicinal plant species and five essential oils were tested for their insecticidal activities against adults of Sitophilus oryzae (L.) and Callosobruchus chinensis (L.), using direct contact application and fumigation methods. Responses varied with plant material, insect species, and exposure time. In a test with a filter paper diffusion method at 3.5 mg/cm², potent insecticidal activity against both species was produced by an extract from Cinnamomum cassia bark, cinnamon (C. cassia) oil, horseradish (Cocholeria aroracia) oil, and mustard (Brassica juncea) oil within 1 day after treatment. Over 90% mortality at 3 or 4 days after treatment was achieved using extracts of Acorus calamus var. angustatus rhizome, Acorus gramineus rhizome, Illicium verum fruit, and Foeniculum vulgare fruit. An extract from Cinnamomum sieboldii root bark gave 100% mortality at 2 days after treatment. At 0.7 mg/cm², extracts from C. cassia, C. sieboldii, and F. vulgare as well as cinnamon oil, horseradish oil and mustard oil were highly effective against both species. In a fumigation test with S. oryzae adults, the oils described were much more effective in closed containers than in open ones, indicating that the insecticidal activity of the oils was attributable to fumigant action. The plant extracts and essential oils described could be useful for managing field populations of S. oryzae and C. chinensis.