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Similar to other pear psylla species in Europe and America, Cacopsylla chinensis (Yang and Li) is one of the most important pests that causes yield loss in commercial pear orchards in China. To investigate effective essential oils as alternatives to conventional pesticides against C. chinensis, 26 essential oils derived from commonly used Chinese spices and medicinal herbs were screened for insecticidal activity. Among these, the essential oil from Perilla frutescens (L.) Britton leaves was the top performer; it exhibited strong and acute toxicity against pear psylla, with an LD50 value of 0.63 μg per adult. Then, we tested the constituents of the essential oil and its toxicity in the field. Field trials showed a 72% corrected reduction in the first-second-instar population 7 d after spraying P. frutescens leaf oil solution at a concentration of 1 mg/ml and a 47% corrected reduction at days 3 and 14. This report is the first to document the application of essential oil from P. frutescens leaves to control C. chinensis under field conditions. Our results suggest that P. frutescens oil can be considered a novel potential pesticide for C. chinensis control in pear orchards., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The essential oil of Stachys riederi var. japonica (Family: Lamiaceae) was extracted by hydrodistillation and determined by GC and GC-MS. A total of 40 components were identified, representing 96.01% of the total oil composition. The major compounds in the essential oil were acetanisole (15.43%), anisole (9.43%), 1,8-cineole (8.07%), geraniol (7.89%), eugenol (4.54%), caryophyllene oxide (4.47%), caryophyllene (4.21%) and linalool (4.07%). Five active constituents (acetanisole, anisole, 1,8-cineole, eugenol and geraniol) were identified by bioactivity-directed fractionation. The essential oil possessed fumigant toxicity against maize weevils ( Sitophilus zeamais ) and booklice ( Liposcelis bostrychophila ), with LC 50 values of 15.0 mg/L and 0.7 mg/L, respectively. Eugenol and anisole exhibited stronger fumigant toxicity than the oil against booklice. 1,8-Cineole showed stronger toxicity, and anisole as well as eugenol exhibited the same level of fumigant toxicity as the essential oil against maize weevils. The essential oil also exhibited contact toxicity against S. zeamais adults and L. bostrychophila , with LC 50 values of 21.8 µg/adult and 287.0 µg/cm², respectively. The results indicated that the essential oil of S. riederi var. japonica and its isolates show potential as fumigants, and for their contact toxicity against grain storage insects.

The screening of Chinese medicinal herbs for insecticidal principles showed that the essential oil of Echinops grijsii Hance roots possessed significant larvicidal activity against mosquitoes. The essential oil was extracted via hydrodistillation and its constituents were determined by gas chromatography-mass spectrometry (GC-MS) analysis. GC-MS analyses revealed the presence of 31 components, with 5-(3-buten-1-yn-1-yl)-2,2'-bithiophene (5-BBT, 27.63%), αterthienyl (α-T, 14.95%),1,8-cineole (5.56%) and cis-β-ocimene (5.01%) being the four major constituents. Based bioactivity-directed chromatographic separation of the essential oil led to the isolation of 5-BBT, 5-(4-isovaleroyloxybut-1-ynyl)-2,2'-bithiophene (5-IBT) and αT as active compounds. The essential oil of E. grijsii exhibited larvicidal activity against the fourth instar larvae of Aedes albopictus, Anopheles sinensis and Culex pipiens pallens with LC50 values of 2.65 μg/mL, 3.43 μg/mL and 1.47 μg/mL, respectively. The isolated thiophenes, 5-BBT and 5-IBT, possessed strong larvicidal activity against the fourth instar larvae of Ae. albopictus(LC50 = 0.34 μg/mL and 0.45 μg/mL, respectively) and An. sinensis(LC50 = 1.36 μg/mL and 5.36 μg/mL, respectively). The two isolated thiophenes also had LC50 values against the fourth instar larvae of C. pipiens pallens of 0.12 μg/mL and 0.33 μg/mL, respectively. The findings indicated that the essential oil of E. grijsii roots and the isolated thiophenes have an excellent potential for use in the control of Ae.albopictus, An. sinensis and C. pipiens pallens larvae and could be used in the search for new, safer and more effective natural compounds as larvicides.

Water-distilled essential oil from Clinopodium chinense (Labiatae) aerial parts at the flowering stage was analyzed by gas chromatography-mass spectrometry. Thirty-five compounds, accounting for 99.18% of the total oil, were identified, and the main components of the essential oil of C. chinense were spathulenol (18.54%), piperitone (18.9%), caryophyllene (12.04%), and bornyl acetate (8.14%). Based on bioactivity-directed fractionation, bornyl acetate, caryophyllene, and piperitone were identified from the essential oil. The essential oil possessed fumigant toxicity against booklice (Liposcelis bostrychophila) with a 50% lethal concentration (LC50) value of 423.39 μg/liter, while the isolated constituents, bornyl acetate and piperitone, had LC50 values of 351.69 and 311.12 μg/liter against booklice, respectively. The essential oil also exhibited contact toxicity against L. bostrychophila with an LC50 value of 215.25 μg/cm(2). Bornyl acetate, caryophyllene, and piperitone exhibited acute toxicity against booklice with LC50 values of 321.42, 275.00, and 139.74 μg/cm(2), respectively. The results indicated that the essential oil and its isolated constituents have potential for development into natural insecticides or fumigants for control of insects in stored grains.

The aim of this study was to evaluate the larvicidal activity of the essential oil of Youngia japonica aerial parts against the larvae of Aedes albopictus and to isolate any active compounds from the oil. Gas chromatography-mass spectrometry (GC-MS) analyses revealed the presence of 31 compounds, with menthol (23.53%), α-asarone (21.54%), 1,8-cineole (5.36%), and caryophyllene (4.45%) as the major constituents. Bioactivity-directed chromatographic separation of the oil led to the isolation of menthol and α-asarone as active compounds. The essential oil of Y. japonica exhibited larvicidal activity against the fourth instar larvae of A. albopictus with an LC₅₀ value of 32.45 μg/mL. α-Asarone and menthol possessed larvicidal activity against the fourth instar larvae of A. albopictus with LC₅₀ values of 24.56 μg/mL and 77.97 μg/mL, respectively. The results indicate that the essential oil of Y. japonica aerial parts and the two constituents can be potential sources of natural larvicides.

The aim of this research was to evaluate contact toxicity and repellency of the essential oil of Pogostemon cablin (Blanco) Bentham leaves against German cockroaches (Blattella germanica) (L.) and to isolate any active constituents. Essential oil of P. cablin leaves was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Twenty-three components were identified in the essential oil, and the main constituents were patchoulol (41.31%), pogostone (18.06%), α-bulnesene (6.56%), caryophyllene (5.96%), and seychellene (4.32%). Bioactivity-directed chromatographic separation of the essential oil led to the isolation of pogostone, patchoulol, and caryophyllene as active compounds. The essential oil of P. cablin leaves exhibited acute toxicity against male B. germanica adults with an LC50 value of 23.45 μg per adult. The constituent compound, pogostone (LC50 = 8.51 μg per adult) showed stronger acute toxicity than patchoulol (LC50 = 207.62 μg per adult) and caryophyllene (LC50 = 339.90 μg per adult) against the male German cockroaches. The essential oil of P. cablin leaves and the three isolated constituents exhibited strong repellent activity against German cockroaches at a concentration of 5 ppm. The results indicated that the essential oil of P. cablin leaves and its major constituents have good potential as a source for natural insecticides and repellents., (© The Author 2015. Published by Oxford University Press on behalf of the Entomological Society of America. For Permissions, please e-mail: journals.permissions@oup.com.)

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.

Hydrodistilled essential oil from Rhododendron anthopogonoides Maxim. (Ericaceae) aerial parts was analysed by gas chromatography-mass spectrometry (GC-MS). A total of 42 compounds, accounting for 95.48% of the total oil, were identified. The main constituents of the essential oil were benzyl acetone (34.41%), nerolidol (10.19%), 1,4-cineole (8.41%), beta-caryophyllene (5.63%), gamma-elemene (5.10%), and spathulenol (3.06%). Four constituents were isolated from the essential oil based on fractionation. The essential oil of R. anthopogonoides possessed nematicidal activity against the root knot nematode (Meloidogyne incognita) with an LC50 value of 130.11 microg/ml. The main compound of the essential oil, benzyl acetone, exhibited nematicidal activity against M. incognita with an LC50 value of 74.17 microg/ml while 1,4-cineole, nerolidol, and beta-caryophyllene were not nematicidal at a concentration of 5 mg/ml. The essential oil of R. anthopogonoides and benzyl acetone show potential for their development as possible natural nematicides for the control of the root knot nematode.

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 the chemical composition and nematicidal activity of essential oil of Agastache rugosa flowering aerial parts against the root knot nematode, Meloidogyne incognita, and to isolate and identify any nematicidal constituents from the essential oil. The essential oil of A. rugosa aerial parts was obtained by hydrodistillation and analyzed by GC-FID and GC-MS. A total of 37 components of the essential oil were identified, with the principal compounds being methyleugenol (50.51%), estragole (8.55%), and eugenol (7.54%), followed by thymol (3.62%), pulegone (2.56%), limonene (2.49%) and caryophyllene (2.38%). Based on bioactivity-guided fractionation, the three active constituents were isolated from the essential oil and identified as methyleugenol, estragole and eugenol. The essential oil of A. rugosa exhibited strong nematicidal activity against M. incognita, with a LC50 value of 47.3 μg/mL. The components eugenol (LC50 = 66.6 μg/mL) and methyleugenol (LC50 = 89.4 μg/mL) exhibited stronger nematicidal activity against M. incognita (LC50 = 185.9 μg/mL). The results indicate that the essential oil of A. rugosa aerial parts and its constituent compounds have potential for development into natural nematicides for control of the root knot nematode.

Water-distilled essential oil from the aerial parts of Dipsacus japonicus Miq. (Dipsacaceae) at the flowering stage was analysed by gas chromatography-mass spectrometry (GC-MS). Forty-six compounds, accounting for 96.76% of the total oil, were identified and the main compounds of the essential oil were linalool (11.78%), trans-geraniol (8.58%), 1,8-cineole (7.91%), beta-caryophyllene (5.58%), alpha-terpineol (5.32%), beta-selinene (5.15%), and spathulenol (5.04%). The essential oil of D. japonicus possessed contact toxicity against two grain storage insects, Sitophilus zeamais and Tribolium castaneum adults, with LD50 values of 18.32 microg/ adult and 13.45 microg/adult, respectively. The essential oil of D. japonicus also exhibited pronounced fumigant toxicity against S. zeamais (LC50 = 10.11 mg/l air) and T. castaneum adults (LC50 = 5.26 mg/l air). Of the three major compounds, 1,8-cineole exhibited stronger fumigant toxicity than the crude essential oil against S. zeamais and T. castaneum adults with LC50 values of 2.96 mg/l air and 4.86 mg/l air, respectively.

The screening for bioactive principles from several Chinese medicinal herbs showed that the essential oil of Cymbopogon distans aerial parts possessed strong repellency against the booklouse, Liposcelis bostrychophila , and the red flour beetle, Tribolium castaneum . A total of 36 components of the essential oil were identified by GC and GC-MS. trans-Geraniol (16.54%), (R)-citronellal (15.44%), (+)-citronellol (11.51%), and α-elemol (9.06%) were the main components of the essential oil followed by β-eudesmol (5.71%) and (+)-limonene (5.05%). From the essential oil, four monoterpenes were isolated by bioassay-guided fractionation. The compounds were identified as limonene, citronellol, citronellal, and trans-geraniol. Geraniol and citronellol were strongly repellent against the booklouse, L. bostrychophila, whereas citronellal and limonene exhibited weak repellency against the booklouse. Geraniol and citronellol exhibited comparable repellency against the booklouse relative to the positive control, DEET. Moreover, geraniol and citronellol exhibited stronger repellency against the red flour beetle than DEET, whereas the two other compounds showed the same level of repellency against the red flour beetle compared with DEET.

The screening of several Chinese medicinal plants for insecticidal principles showed that essential oil of Rhododendron anthopogonoides flowering aerial parts possessed significant toxicity against maize weevils, Sitophilus zeamais. A total of 37 components were identified in the essential oil and the main constituents of the essential oil were 4-phenyl-2-butanone (27.22%), nerolidol (8.08%), 1,4-cineole (7.85%), caryophyllene (7.63%) and γ-elemene (6.10%), followed by α-farnesene (4.40%) and spathulenol (4.19%). Repeated bioactivity-directed chromatographic separation on silica gel columns led us to isolate three compounds, namely 4-phenyl-2-butanone, 1,4-cineole, and nerolidol. 4-Phenyl-2-butanone shows pronounced contact toxicity against S. zeamais (LD₅₀ = 6.98 mg/adult) and was more toxic than either 1,4-cineole or nerolidol (LD₅₀ = 50.86 mg/adult and 29.30 mg/adult, respectively) against the maize weevils, while the crude essential oil had a LD₅₀ value of 11.67 mg/adult. 4-Phenyl-2-butanone and 1,4-cineole also possessed strong fumigant toxicity against the adults of S. zeamais (LC₅₀ = 3.80 mg/L and 21.43 mg/L) while the crude essential oil had a LC₅₀ value of 9.66 mg/L.