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The aim of this research was to determine chemical composition and repellent and insecticidal activities of the essential oil of Kaempferia galanga L. rhizomes against the booklouse, Liposcelis bostrychophila Badonnel, and to isolate insecticidal or repellent constituents from the oil. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. Twenty-eight components of the oil were identified. The major compounds in the oil were ethyl-rho-methoxycinnamate (38.6%), ethyl cinnamate (23.2%), 1,8-cineole (11.5%), trans-cinnamaldehyde (5.3%), and borneol (5.2%). Based on bioactivity-guided fractionation, four active constituents were isolated from the oil and identified as 1,8-cineole, ethyl cinnamate, ethyl rho-methoxycinnamate, and trans-cinnamaldehyde. The essential oil exhibited contact toxicity against the booklouse with an LC50 value of 68.6 microg/cm2. Ethyl cinnamate (LC50 = 21.4 microg/cm2) exhibited stronger contact toxicity than ethyl rho-methoxycinnamate and trans-cinnamaldehyde (LC50 = 44.6 and 43.4 microg/cm2, respectively) while 1,8-cineole showed weak acute toxicity. The essential oil also possessed fumigant toxicity against the booklouse with a LC50 value of 1.5 mg/liter air. 1,8-Cineole and trans-cinnamaldehyde (LC50 = 1.1 and 1.3 mg/liter, respectively) possessed stronger fumigant toxicity against the booklouse than ethyl cinnamate and ethyl rho-methoxycinnamate (LC50 = 10.2 and 10.2 mg/liter air, respectively). trans-Cinnamaldehyde was strongly repellent to booklice, whereas ethyl cinnamate and ethyl rho-methoxycinnamate were weakly repellent and 1,8-cineole did not repel booklice. The results indicate that the essential oil and its constituent compounds have potential for development into natural insecticides or fumigants and repellents for control of insects in stored grains.

In our screening program for insecticidal activity of the essential oils/extracts derived from some Chinese medicinal herbs and spices, garlic (Allium sativum L.) essential oil was found to possess strong insecticidal activity against overwintering adults of Cacopsylla chinensis Yang et Li (Hemiptera: Psyllidae). The commercial essential oil of A. sativum was analyzed by gas chromatography-mass spectrometry. Sixteen compounds, accounting for 97.44% of the total oil, were identified, and the main components of the essential oil of A. sativum were diallyl trisulfide (50.43%), diallyl disulfide (25.30%), diallyl sulfide (6.25%), diallyl tetrasulfide (4.03%), 1,2-dithiolane (3.12%), allyl methyl disulfide (3.07%), 1,3-dithiane (2.12%), and allyl methyl trisulfide (2.08%). The essential oil of A. sativum possessed contact toxicity against overwintering C. chinensis, with an LC50 value of 1.42 microg per adult. The two main constituent compounds, diallyl trisulfide and diallyl disulfide, exhibited strong acute toxicity against the overwintering C. chinensis, with LC50 values of 0.64 and 11.04 /g per adult, respectively.

The aim of this research was to determine chemical composition and repellent and insecticidal activities of the essential oil of Kaempferia galanga L. rhizomes against the booklouse, Liposcelis bostrychophila Badonnel, and to isolate insecticidal or repellent constituents from the oil. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. Twenty-eight components of the oil were identified. The major compounds in the oil were ethyl-rho-methoxycinnamate (38.6%), ethyl cinnamate (23.2%), 1,8-cineole (11.5%), trans-cinnamaldehyde (5.3%), and borneol (5.2%). Based on bioactivity-guided fractionation, four active constituents were isolated from the oil and identified as 1,8-cineole, ethyl cinnamate, ethyl rho-methoxycinnamate, and trans-cinnamaldehyde. The essential oil exhibited contact toxicity against the booklouse with an LC50 value of 68.6 microg/cm2. Ethyl cinnamate (LC50 = 21.4 microg/cm2) exhibited stronger contact toxicity than ethyl rho-methoxycinnamate and trans-cinnamaldehyde (LC50 = 44.6 and 43.4 microg/cm2, respectively) while 1,8-cineole showed weak acute toxicity. The essential oil also possessed fumigant toxicity against the booklouse with a LC50 value of 1.5 mg/liter air. 1,8-Cineole and trans-cinnamaldehyde (LC50 = 1.1 and 1.3 mg/liter, respectively) possessed stronger fumigant toxicity against the booklouse than ethyl cinnamate and ethyl rho-methoxycinnamate (LC50 = 10.2 and 10.2 mg/liter air, respectively). trans-Cinnamaldehyde was strongly repellent to booklice, whereas ethyl cinnamate and ethyl rho-methoxycinnamate were weakly repellent and 1,8-cineole did not repel booklice. The results indicate that the essential oil and its constituent compounds have potential for development into natural insecticides or fumigants and repellents for control of insects in stored grains.

In our screening program for insecticidal activity of the essential oils/extracts derived from some Chinese medicinal herbs and spices, garlic (Allium sativum L.) essential oil was found to possess strong insecticidal activity against overwintering adults of Cacopsylla chinensis Yang et Li (Hemiptera: Psyllidae). The commercial essential oil of A. sativum was analyzed by gas chromatography-mass spectrometry. Sixteen compounds, accounting for 97.44% of the total oil, were identified, and the main components of the essential oil of A. sativum were diallyl trisulfide (50.43%), diallyl disulfide (25.30%), diallyl sulfide (6.25%), diallyl tetrasulfide (4.03%), 1,2-dithiolane (3.12%), allyl methyl disulfide (3.07%), 1,3-dithiane (2.12%), and allyl methyl trisulfide (2.08%). The essential oil of A. sativum possessed contact toxicity against overwintering C. chinensis, with an LC50 value of 1.42 microg per adult. The two main constituent compounds, diallyl trisulfide and diallyl disulfide, exhibited strong acute toxicity against the overwintering C. chinensis, with LC50 values of 0.64 and 11.04 /g per adult, respectively.