Bioactivities of essential oil from Elletaria cardamomum (L.) Maton. to Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst)

Contact and fumigant toxicities and antifeedant activity of the essential oil of cardamom, Elletaria cardamomum, to two stored-product insects, Sitophilus zeamais and Tribolium castaneum, were investigated. Topical application was employed for contact toxicity studies, and filter paper impregnation was used for testing fumigant action. The adults of S. zenmais and T. castaneum were equally susceptible to the contact toxicity of the oil at the LD50 level, with LD50 values of 56 and 52 mu g mg(-1) insect respectively. However, S. zeamais was more susceptible than T. castaneum at the LD95 level. For fumigant toxicity, S. zeamais adults were more than twice as susceptible as T. castaneum adults at both LD50 and LD95 levels. Furthermore, 12-day larvae of T, castaneum were more tolerant than the adults to the contact toxicity of the oil, but 14- and 16-day larvae had the same susceptibility as the adults. The susceptibility of the larvae to contact toxicity increased with age. In contrast, all the larvae (12-16 days old) of T. castaneum were much more tolerant than the adults to the fumigant action, and larvae of different ages had similar susceptibility. Cardamom oil applied to filter papers in the concentration range 1.04-2.34 mg cm(-2) significantly (P < 0.05) reduced the hatching of T. castaneum eggs and the subsequent survival rate of the larvae. Adult emergence was also drastically reduced by cardamom oil. When applied to rice or wheat, the oil totally suppressed F1 progeny production of both insects at a concentration of 5.3 x 10(3) ppm. Feeding deterrence studies showed that cardamom oil did not have any growth inhibitory or feeding deterrence effects on either adults or larvae of T. castaneum. However, it significantly reduced all the nutritional indices of the adults of S, zeamais, but with very slight feeding deterrence (27%) at a concentration of 1.44 x 10(4) ppm. (C) 2000 Elsevier Science Ltd. All rights reserved.