Toxicity of Juniperus oxycedrus oil constituents and related compounds and the efficacy of oil spray formulations to Dermatophagoides farinae (Acari: Pyroglyphidae).

The American house dust mite (AHDM), Dermatophagoides farinae Hughes (Acari: Pyroglyphidae), is recognized as an important source of allergens in the domestic environment. This study was conducted to determine whether 19 constituents from essential oil of cade, Juniperus oxycedrus L. (Cupressaceae), eight structurally related compounds, and another 16 previously known cade oil constituents were toxic for adult AHDMs and to determine the route of acaricidal action of the test compounds, as well as to assess the control efficacy of four experimental spray formulations containing the oil (10-40 mg/L sprays). In a fabric-circle contact mortality bioassay, methyleugenol (LD50, 5.82 µg/cm2) and guaiacol (8.24 µg/cm2) were the most toxic compounds against the mites, and the toxicity of these compounds and benzyl benzoate did not significantly differ. High toxicity was also observed with eugenol, m-cresol, and nerolidol (LD50, 12.52-19.52 µg/cm2), and these compounds were significantly more toxic than N,N-diethyl-3-methylbenzamide (DEET) (LD50, 37.67 µg/cm2). Cade applied as 30 or 40 mg/L experimental sprays provided 96 and 100% mortality against the mites, respectively, whereas permethrin (cis:trans, 25:75) 2.5 g/L spray treatment resulted in 17% mortality. In vapor-phase mortality tests, the compounds described were consistently more toxic in closed versus open containers, indicating that toxicity was achieved mainly through the action of vapor. Reasonable mite control in indoor environments can be achieved by spray formulation containing the 40 mg/L cade oil as potential contact-action fumigants.

Identification and field evaluation of the sex pheromone of Synanthedon bicingulata (Staudinger).

The sex pheromone of Synanthedon bicingulata (Staudinger), a major pest of Prunus species in many regions of northeast Asia, was identified. Two major components from the pheromone gland extracts of female moths are (E,Z)-3,13-octadecadienyl acetate (E3,Z13-18:OAc) and (Z,Z)-3,13-octadecadienyl acetate (Z3,Z13-18:OAc), and the average ratio of these components is about 4:6, respectively. In addition to the major components, four minor components, (Z)-13-octadecenyl acetate (Z13-18:OAc), (E,Z)-2,13-octadecadienyl acetate (E2,Z13-18:OAc), (E,Z)-3,13-octadecadien-1-ol (E3,Z13-18:OH), and (Z,Z)-3,13-octadecadien-1-ol (Z3,Z13-18:OH) also were identified from pheromone gland extracts. Field tests showed that E3,Z13-18:OAc and Z3,Z13-18:OAc are essential for attraction of male S. bicingulata moths, and males are optimally attracted to the blend ratio found in pheromone gland extracts of conspecific females. Addition of the minor glandular components (Z13-18:OAc, E2,Z13-18:OAc, E3,Z13-18:OH, and Z3,Z13-18:OH) did not affect captures of males to the primary binary blend. Thus, the blend of E3,Z13-18:OAc and Z3,Z13-18:OAc at the natural ratio can be used for monitoring populations of this species.

Repellency to Stomoxys calcitrans (Diptera: Muscidae) of plant essential oils alone or in combination with Calophyllum inophyllum nut oil.

The repellency to female Stomoxys calcitrans (L.) (Diptera: Muscidae) of 21 essential oils (EOs) alone or in combination with Calophyllum inophyllum L. (Clusiaceae) nut oil (tamanu oil) was examined using an exposed human hand bioassay. Results were compared with those of commonly used repellent N,N-diethyl-3-methylbenzamide (DEET). In tests with six human male volunteers at a dose of 0.5 mg/cm2, patchouli (protection time [PT], 3.67 h) was the most effective EO but less active than DEET (4.47 h), as judged by the PT to first bite. Very strong repellency also was produced by clove bud, lovage root, and clove leaf EOs (PT, 3.50-3.25 h), whereas strong repellency was obtained from thyme white EO (2.12 h). Thyme red, oregano, and geranium EOs exhibited moderate repellency (PT, 1.24-1.11 h). At 0.25 mg/cm2, protection time of clove bud, clove leaf, and lovage root EOs (PT, approximately equal to 1 h) was shorter than that of DEET (2.17 h). An increase in the protection time was produced by binary mixtures (PT, 2.68-2.04 h) of five EOs (clove bud, clove leaf, thyme white, patchouli, and savory) and tamanu oil (0.25:2.0 mg/cm2) compared with that of either the constituted essential oil or tamanu oil alone (PT, 0.56 h). The protection time of these binary mixtures was comparable with that of DEET. With the exception of savory EO, the other EOs, tamanu oil, and binary mixtures did not induce any adverse effects on the human volunteers at 0.5 mg/cm2. Thus, binary mixtures of essential oils and tamanu oil described merit further study as potential repellents for protection from humans and domestic animals from biting and nuisance caused by S. calcitrans.

Insecticidal activities of their components derived from the essential oils of Cinnamomum sp. barks and against Ricania sp. (Homoptera: Ricaniidae), a newly recorded pest.

BACKGROUND: Insecticidal activities of Cinnamomum cassia and Cinnamomum zeylanicum oils and their components are not known against Ricania sp. Insecticidal activities of major components derived from C. cassia and C. zeylanicum oils were examined in spray and leaf-dipping bioassays against Ricania sp. nymphs and adults. RESULTS: The LC50 value of C. cassia and C. zeylanicum oils was 37.66 and 72.62 mg L-1 , respectively, in leaf-dipping bioassays against Ricania sp. nymphs, and 77.38 and 134.86 mg L-1 in spray bioassays against Ricania sp. adults. The insecticidal activity of C. cassia oil was 1.74-1.93 times greater than that of C. zeylanicum oil. When examined by gas chromatography mass spectrometry, the cinnamaldehyde content of C. cassia and C. zeylanicum oils was 80.20% and 46.32%, respectively. Based on the LC50 values of cinnamaldehyde, hydrocinnamaldehyde and 4-hydroxy-3-methoxycinnamaldehyde against Ricania sp. nymphs and adults, cinnamaldehyde (LC50 , 31.25 and 62.43 mg L-1 ) demonstrated the most potent insecticidal activity, followed by 4-hydroxy-3-methoxycinnamaldehyde (172.19 and 212.77 mg L-1 ) and hydrocinnamaldehyde (275.05 and 318.63 mg L-1 ). CONCLUSION: The findings revealed that C. cassia oil, C. zeylanicum oil and cinnamaldehyde have potential value in the management of Ricania sp. and could be valuable as effective insecticides. © 2017 Society of Chemical Industry.

Isolation of Insecticidal Constituent from Ruta graveolens and Structure-Activity Relationship Studies against Stored-Food Pests (Coleoptera).

Isolates from essential oil extracted from the flowers and leaves of Ruta graveolens and commercial phenolic analogs were evaluated using fumigant and contact toxicity bioassays against adults of the stored-food pests Sitophilus zeamais, Sitophilus oryzae, and Lasioderma serricorne. The insecticidal activity of these compounds was then compared with that of the synthetic insecticide dichlorvos. To investigate the structure-activity relationships, the activity of 2-isopropyl-5-methylphenol and its analogs was examined against these stored-food pests. Based on the 50% lethal dose, the most toxic compound against S. zeamais was 3-isopropylephenol, followed by 2-isopropylphenol, 4-isopropylphenol, 5-isopropyl-2-methylphenol, 2-isopropyl-5-methylphenol, 3-methylphenol, and 2-methylphenol. Similar results were observed with phenolic compounds against S. oryzae. However, when 2-isopropyl-5-methylphenol isolated from R. graveolens oil and its structurally related analogs were used against L. serricorne, little or no insecticidal activity was found regardless of bioassay. These results indicate that introducing and changing the positions of functional groups in the phenol skeleton have an important effect on insecticidal activity of these compounds against stored-food pests.

Fumigant toxicity of basil oil compounds and related compounds to Thrips palmi and Orius strigicollis.

BACKGROUND: This study was aimed at assessing the fumigant toxicity to adult Thrips palmi (a serious insect pest) and Orius strigicollis (a beneficial predator insect) of basil (Ocimum basilicum) essential oil compounds and structurally related compounds using vapour-phase toxicity bioassays. RESULTS: Against adult T. palmi, linalool (LD50 0.0055 mg cm(-3) ) was the most toxic fumigant and was 15.2-fold more effective than dichlorvos (0.0837 mg cm(-3) ). Strong fumigant toxicity was also observed in pulegone (0.0095 mg cm(-3) ), (±)-camphor (0.0097 mg cm(-3) ) and 1,8-cineole (0.0167 mg cm(-3) ). Moderate toxicity was produced by camphene, 3-carene, (-)-menthone, (+)-α-pinene, (+)-ß-pinene, α-terpineol and (-)-α-thujone (0.0215-0.0388 mg cm(-3) ). Against adult O. strigicollis, dichlorvos (LD50 9.0 × 10(-10) mg cm(-3) ) was the most toxic fumigant, whereas the LD50 values of these compounds ranged from 0.0127 to >0.23 mg cm(-3) . Based upon the selective toxicity ratio, the compounds described are more selective than dichlorvos. CONCLUSION: The basil oil compounds described merit further study as potential insecticides for control of T. palmi in greenhouses because of their generally lower toxicity to O. strigicollis and their greater activity as a fumigant than dichlorvos.

A piperidine amide extracted from Piper longum L. fruit shows activity against Aedes aegypti mosquito larvae.

Mosquito larvicidal activity of Piper longum fruit-derived materials against the fourth-instar larvae of Aedes aegypti was examined. A crude methanol extract of P. longum fruits was found to be active against the larvae, and the hexane fraction of the methanol extract showed a strong larvicidal activity of 100% mortality. The biologically active component of P. longum fruits was characterized as pipernonaline by spectroscopic analyses. The LC(50) value of pipernonaline was 0.25 mg/L. The toxicity of pipernonaline is comparable to that of pirimiphos-methyl as a mosquito larvicide. In tests with available components derived from P. longum, no activity was observed with piperettine, piperine, or piperlongumine.

Fumigant toxicity of lemon eucalyptus oil constituents to acaricide-susceptible and acaricide-resistant Tetranychus urticae.

BACKGROUND: This study was aimed at assessing the fumigant toxicity of 14 essential oil constituents from lemon eucalyptus, Eucalyptus citriodora Hook, and another ten known compounds to females of acaricide-susceptible, chlorfenapyr-resistant, fenpropathrin-resistant, pyridaben-resistant and abamectin-resistant strains of Tetranychus urticae Koch. RESULTS: Menthol (LC(50) , 12.9 µg cm(-3) ) was the most toxic compound, followed by citronellyl acetate (16.8 µg cm(-3) ), against the susceptible females. High toxicity was also produced by ß-citronellol, citral, geranyl acetate and eugenol (LC(50) , 21.7-24.6 µg cm(-3) ). The fumigant toxicity of these compounds was almost identical against females from either of the susceptible and resistant strains, indicating that the compounds and acaricides do not share a common mode of action or elicit cross-resistance. CONCLUSION: Global efforts to reduce the level of highly toxic synthetic acaricides in the agricultural environment justify further studies on materials derived from lemon eucalyptus oil, particularly menthol and citronellyl acetate, as potential acaricides for the control of acaricide-resistant T. urticae as fumigants with contact action.