Effect of Different Selenium Species on Indole-3-Acetic Acid Activity of Selenium Nanoparticles Producing Strain Bacillus altitudinis LH18.

Acting as a growth regulator, Indole-3-acetic acid (IAA) is an important phytohormone that can be produced by several Bacillus species. However, few studies have been published on the comprehensive evaluation of the strains for practical applications and the effects of selenium species on their IAA-producing ability. The present study showed the selenite reduction strain Bacillus altitudinis LH18, which is capable of producing selenium nanoparticles (SeNPs) at a high yield in a cost-effective manner. Bio-SeNPs were systematically characterized by using DLS, zeta potential, SEM, and FTIR. The results showed that these bio-SeNPs were small in particle size, homogeneously dispersed, and highly stable. Significantly, the IAA-producing ability of strain was differently affected under different selenium species. The addition of SeNPs and sodium selenite resulted in IAA contents of 221.7 µg/mL and 91.01 µg/mL, respectively, which were 3.23 and 1.33 times higher than that of the control. This study is the first to examine the influence of various selenium species on the IAA-producing capacity of Bacillus spp., providing a theoretical foundation for the enhancement of the IAA-production potential of microorganisms.

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.

Acaricidal activity of Asarum heterotropoides root-derived compounds and hydrodistillate constitutes toward Dermanyssus gallinae (Mesostigmata: Dermanyssidae).

The acaricidal activity of Asarum heterotropoides root-derived principles, methyleugenol, safrole, 3-carene, α-asarone, pentadecane and A. heterotropoides root steam distillate constituents was tested against poultry red mites Dermanyssus gallinae (De Geer). All active principles were identified by spectroscopic analysis. Results were compared with those of two conventional acaricides, benzyl benzoate and N,N-diethyl-3-methylbenzamide (DEET). Methyleugenol (24 h LC50 = 0.57 µg/cm(2)) and safrole (24 h LC50 = 8.54 µg/cm(2)) were the most toxic compounds toward D. gallinae, followed by 3,4,5-trimethoxytoluene, 3,5-dimethoxytoluene, estragole, α-terpineol, verbenone, eucarvone, linalool, and terpinen-4-ol (LC50 = 15.65-27.88 µg/cm(2)). Methyleugenol was 16.7× and 11.0× more toxic than benzyl benzoate (LC50 = 9.52 µg/cm(2)) and DEET (LC50 = 6.28 µg/cm(2)), respectively; safrole was 1.1× and 0.73× more toxic. Asarum heterotropoides root-derived materials, particularly methyleugenol and safrole, merit further study as potential acaricides. Global efforts to reduce the level of highly toxic synthetic acaricides in indoor environments justify further studies on A. heterotropoides root extract and steam distillate preparations containing the active constituents described as potential contact-action fumigants for the control of mites.

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

Pyroglyphid house dust mites are the most common cause of allergic symptoms in humans. An assessment was made of the toxicity of basil, Ocimum basilicum L, essential oil, 11 basil oil constituents, seven structurally related compounds, and another 22 previously known basil oil constituents to adult American house dust mites, Dermatophagoides farinae Hughes. The efficacy of four experimental spray formulations containing basil oil (1, 2, 3, and 4% sprays) was also assessed. Results were compared with those of two conventional acaricides benzyl benzoate and N,N-diethyl-3-methylbenzamide. The active principles of basil oil were determined to be citral, alpha-terpineol, and linalool. Citral (24 h LC50, 1.13 microg/cm2) and menthol (1.69 microg/cm2) were the most toxic compounds, followed by methyl eugenol (5.78 microg/cm2). These compounds exhibited toxicity greater than benzyl benzoate (LC50, 8.41 microg/cm2) and N,N-diethyl-3-methylbenzamide (37.67 microg/cm2). Potent toxicity was also observed with eugenol, menthone, spathulenol, alpha-terpineol, nerolidol, zerumbone, and nerol (LC50, 12.52-21.44 microg/cm2). Interestingly, the sesquiterpenoid alpha-humulene, lacking only the carbonyl group present in zerumbone, was significantly less effective than zerumbone, indicating that the alpha,beta-unsaturated carbonyl group of zerumbone is a prerequisite component for toxicity. These compounds were consistently more toxic in closed versus open containers, indicating that their mode of delivery was largely a result of vapor action. Basil oil applied as 3 and 4% sprays provided 97 and 100% mortality against the mites, respectively, whereas permethrin (cis:trans, 25:75) 2.5 g/liter spray treatment resulted in 17% mortality. Our results indicate that practical dust mite control in indoor environments can be achieved by basil oil spray formulations (3 and 4% sprays) as potential contact-action fumigants.

Predation and control efficacies of Misgurnus mizolepis (Cypriniformes: Cobitidae) toward Culex pipiens molestus (Diptera: Culicidae) and fish toxicity of temephos in laboratory and septic tank conditions.

Culex pipiens molestus Forskal (Diptera: Culicidae) is the dominant mosquito species in septic tanks in South Korea. An assessment was made of the biological control potential of mud loaches, Misgurnus mizolepis Günther (Cypriniformes: Cobitidae), toward Cx. p. molestus larvae in laboratory and septic tanks. Results were compared with those of temephos 20% emulsifiable concentrate. In laboratory tests, all mud loaches survived on sedimentation chamber- and effluent chamber-collected water of aerobic septic tanks (ASTs), whereas all mud loaches died within 3-12 h after introduction into sedimentation chamber- and effluent chamber-collected water of anaerobic septic tanks, Gill hyperplasia and hemorrhages at the bases of pectoral fins were detected in all dead mud loaches. These appeared to have been caused by bacterial disease, rather than the physical and chemical characteristics of the septic tank water. A mud loach consumed an average range of 1,072-1,058 larvae of Cx. p. molestus in the AST water at 24 h. At the manufacturer's recommended rate (10 ml/ton) in the AST water, the temephos formulation did not cause fish mortality. In the AST experiment, predation of mosquito larvae by mud loaches at a release rate of one fish per 900 mosquito larvae resulted in complete mosquito control from the third day after treatment throughout the 18-wk survey period, compared with temephos 20% emulsifiable concentrate-treated AST water (reduction rate, 40% at 28 days after treatment). Reasonable mosquito control in aerobic septic tanks can be achieved by mosquito breeding season stocking of a rate of one mud loach per 900 mosquito larvae.

Effects of curcuminoids identified in rhizomes of Curcuma longa on BACE-1 inhibitory and behavioral activity and lifespan of Alzheimer's disease Drosophila models.

BACKGROUND: Alzheimer's disease (AD) is the most common type of presenile and senile dementia. The human ß-amyloid precursor cleavage enzyme (BACE-1) is a key enzyme responsible for amyloid plaque production, which implicates the progress and symptoms of AD. Here we assessed the anti-BACE-1 and behavioral activities of curcuminoids from rhizomes of Curcuma longa (Zingiberaceae), diarylalkyls curcumin (CCN), demethoxycurcumin (DMCCN), and bisdemethoxycurcumin (BDMCCN) against AD Drosophila melanogaster models. METHODS: Neuro-protective ability of the curcuminoids was assessed using Drosophila melanogaster model system overexpressing BACE-1 and its substrate APP in compound eyes and entire neurons. Feeding and climbing activity, lifespan, and morphostructural changes in fly eyes also were evaluated. RESULTS: BDMCCN has the strongest inhibitory activity toward BACE-1 with 17 µM IC50, which was 20 and 13 times lower than those of CCN and DMCCN respectively. Overexpression of APP/BACE-1 resulted in the progressive and measurable defects in morphology of eyes and locomotion. Remarkably, supplementing diet with either 1 mM BDMCCN or 1 mM CCN rescued APP/BACE1-expressing flies and kept them from developing both morphological and behavioral defects. Our results suggest that structural characteristics, such as degrees of saturation, types of carbon skeleton and functional group, and hydrophobicity appear to play a role in determining inhibitory potency of curcuminoids on BACE-1. CONCLUSION: Further studies will warrant possible applications of curcuminoids as therapeutic BACE-1 blockers.

The Fumigation Toxicity of Three Benzoate Compounds against Phosphine-Susceptible and Phosphine-Resistant Strains of Rhyzopertha dominica and Sitophilus oryzae.

Phosphine (PH3) has been widely used as a fumigant in food storage, but increasing PH3 resistance in major pests makes finding alternative fumigants urgent. Methyl benzoate (MBe), a volatile organic compound regarded to be a food-safe natural product, has recently demonstrated significant toxicity against a variety of insect pests. This study is the first evaluation of the fumigation toxicity of three benzoate compounds, MBe, vinyl benzoate, and ethyl benzoate, against PH3-susceptible and PH3-resistant strains of Rhyzopertha dominica and Sitophilus oryzae. All strains were exposed to the compounds at concentrations up to 20 µL/1.5 L air for 24 h. Compared to vinyl benzoate and ethyl benzoate, MBe induced higher mortality rates in all strains at all concentrations. When food was made available, the lethal median concentration for MBe was 10-17-fold higher than when tested without food. Moreover, no significant differences were observed between the responses of the PH3-susceptible and PH3-resistant strains to the compounds. Notably, S. oryzae was more susceptible to MBe. In laboratory settings, MBe successfully controlled PH3-resistant strains of R. dominica and S. oryzae, making it a viable option for PH3-resistance management. Thus, MBe might be suitable for food security programs as an environmentally benign alternative fumigant.

Phosphine gas in the dark induces severe phytotoxicity in Arabidopsis thaliana by increasing a hypoxia stress response and disrupting the energy metabolism: Transcriptomic approaches.

Phosphine (PH3) is an ideal fumigant alternative on methyl bromide (MB) as MB has been classified as an ozone-depleting substance. However, several challenges limit its efficient use in crop production, including the emergence of PH3-resistant insect pests and the incidence of phytotoxic effects on nursery plants. Therefore, this study aims to elucidate the mechanism underlying PH3 phytotoxicity in plants using transcriptomic techniques. Fumigation with 2 g/m3 PH3 induced phytotoxic effects in A. thaliana, as evidenced by a decrease in growth and vegetation indices compared to the control group. Transcriptomic analysis revealed that PH3 fumigation phytotoxicity responses in A. thaliana involve genes related to hypoxia stress and energy metabolism. Additionally, pretreatment with ethylene induced pre-adaptation to hypoxia under light conditions during fumigation effectively suppressed the phytotoxic effects of PH3 in A. thaliana by increasing the expression of hypoxia-adaptive genes. Moreover, the phytotoxicity of PH3 was also confirmed in pumpkin (Cucurbita moschata Duch.), and was dependent on light. Overall, our findings showed that fumigation under light conditions and ethylene pretreatment could be used to minimize PH3-induced phytotoxic effects in plants.

Toxicological and molecular adverse effect of Illicium verum fruit constituents toward Bradysia procera.

BACKGROUND: Bradysia procera, a ginseng stem fungus gnat, is one of the most serious insect pests of Korean ginseng (Panax ginseng), causing significant damage to plant growth. The goal of this study was to determine the toxicity and mechanism of action of phenylpropanoids (trans-anethole and estragole) isolated from the methanol extract and hydrodistillate of Illicium verum fruit against third-instar larvae and eggs of Bradysia procera. RESULTS: The filter-paper mortality bioassay revealed that estragole [median lethal concentration (LC50 ) = 4.68 g/cm2 ] has a significant fumigant effect, followed by trans-anethole (LC50 = 43.92 g/cm2 ). However, estragole had the lowest toxic effect when compared to commercially available insecticides. After 7 days, estragole and trans-anethole at 75 g/cm2 inhibited egg hatchability up to 97% and 93%, respectively. At 0.09 g/cm2 , insecticides had an inhibitory effect on egg-hatching ability ranging from 88% to 94%. Furthermore, in both closed and open containers, these active constituents were able to consistently induce vapor-phased toxicity. Both estragole and trans-anethole have the ability to inhibit acetylcholinesterase (AChE), which is involved in neurotransmitter function. However, the active constituent estragole from I. verum fruit acted as a potent AChE inhibitor and had a slightly lower effect on cyclic adenosine monophosphate (AMP) than octopamine alone. CONCLUSION: This finding suggests that estragole may influence Bradysia procera neurotransmitter function via both the AChE and octopaminergic receptors. More research is needed to demonstrate the potential applications of I. verum fruit-derived products as potential larvicides and ovicides for Bradysia procera population control. © 2022 Society of Chemical Industry.

Enhanced toxicity of binary mixtures of larvicidal constituents from Asarum heterotropoides root to Culex pipiens pallens (Diptera: Culicidae).

The toxicity of pellitorine alone or in combination with (-)-asarinin, alpha-asarone, methyleugenol, or pentadecane (1:1, 1:2, 1:3, 2:1, and 3:1 ratios) to third instars from an insecticide-susceptible KS-CP strain and -resistant DJ-CP colony of Culex pipiens pallens Coquillett was evaluated using a direct-contact mortality bioassay. The binary mixture of pellitorine and (-)-asarinin (3:1 ratio) was significantly more toxic against KS-CP larvae (0.95 mg/liter) and DJ-CP larvae (1.07 mg/liter) than either pellitorine (2.08 mg/liter for KS-CP and 2.33 mg/liter for DJ-CP) or (-)-asarinin (11.45 and 12.61 mg/liter) alone. The toxicity of the other binary mixtures (1:1, 1:2, 1:3, and 2:1 ratios) and pellitorine did not differ significantly from each other. Based on the co-toxicity coefficient (CC) and synergistic factor (SF), the three binary mixtures (1:3, 2:1, and 3:1) operated synergistically (CC, 250-390 and SF, 1.4-2.2 for KS-CP; CC, 257-279 and SF, 1.1-2.1 for DJ-CP). The binary mixtures of pellitorine and (-)-asarinin merit further study as potential larvicides for the control of insecticide-resistant mosquito populations.

Fumigant toxicity of plant essential oils against Camptomyia corticalis (Diptera: Cecidomyiidae).

The toxicity of 98 plant essential oils against third instars of cecidomyiid gall midge Camptomyia corticalis (Loew) (Diptera: Cecidomyiidae) was examined using a vapor-phase mortality bioassay. Results were compared with that of a conventional insecticide dichlorvos. Based on 24-h LC50 values, all essential oils were less toxic than dichlorvos (LC50, 0.027 mg/cm3). The LC50 of caraway (Carum carvi L.) seed, armoise (Artemisia vulgaris L.), clary sage (Salvia sclarea L.), oregano (Origanum vulgare L.), lemongrass [Cymbopogon citratus (DC.) Stapf], niaouli (Melaleuca viridiflora Gaertner), spearmint (Mentha spicata L.), cassia especial (Cinnamomum cassia Nees ex Blume), Dalmatian sage (Salvia offcinalis L.), red thyme (Thymus vulgaris L.), bay [Pimenta racemosa (P. Mill.) J.W. Moore], garlic (Allium sativum L.), and pennyroyal (Mentha pulegium L.) oils is between 0.55 and 0.60 mg/cm3. The LC50 of cassia (C. cassia, pure and redistilled), white thyme (T. vulgaris), star anise (Illicium verum Hook.f.), peppermint (Mentha X piperita L.), wintergreen (Gaultheria procumbens L.), cinnamon (Cinnamomum zeylanicum Blume) bark, sweet marjoram (Origanum majorana L.), Roman chamomile [Chamaemelum nobile (L.) All.], eucalyptus (Eucalyptus globulus Labill.), rosemary (Rosmarinus officinalis L.),Virginian cedarwood (Juniperus virginiana L.), pimento berry [Pimenta dioica (L.) Merr.], summer savory (Satureja hortensis L.), lavender (Lavandula angustifolia Mill.), and coriander (Coriandrum sativum L.) oils is between 0.61 and 0.99 mg/cm3. All other essential oils tested exhibited low toxicity to the cecidomyiid larvae (LC50, >0.99 mg/cm3). Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the active essential oils as potential larvicides for the control of C. corticalis populations as fumigants with contact action.

Nanoemulsion and Encapsulation Strategy of Hydrophobic Oregano Essential Oil Increased Human Prostate Cancer Cell Death via Apoptosis by Attenuating Lipid Metabolism.

Origanum vulgare essential oil (EO) is traditionally well-known for its aromatic properties and biomedical applications, including anticancer. This was the first report where oregano essential oil-based nano emulsion (OENE) was synthesized for studying its effects on prostate cancer cell lines (PC3). At first, we have synthesized OENE and characterized using various spectroscopic analyses. The toxicity and inhibitory concentration (IC50) of OENE toward prostate cancer by MTT analysis were performed. The lipid biogenesis mediated, molecular target pathway analyses were performed using fluorescence cellular staining techniques, real-time RT-PCR, or western blotting analysis. OENE showed IC50 at 13.82 µg/mL and significantly induced distinct morphological changes, including cell shrinkage, cell density, and cell shape reduction. In addition, OENE could also significantly decreased lipid droplet accumulation which was confirmed by studying mRNA transcripts of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) (0.31-fold), fatty acid synthase (FASN) (0.18-fold), and sterol regulatory element-binding protein (SREPB1) (0.11-fold), respectively. Furthermore, there is a significant upregulation BAX (BCL2 associated X) and caspase 3 expressions. Nevertheless, OENE decreased the transcript level of BCL2 (B-cell lymphoma 2), thus resulting in apoptosis. Overall, our present work demonstrated that OENE could be a therapeutic target for the treatment of prostate cancer and warrants in vivo studies.

Identification and characterization of chlorpyrifos-methyl and 3,5,6-trichloro-2-pyridinol degrading Burkholderia sp. strain KR100.

A chlorpyrifos-methyl (CM) degrading bacterium (designated strain KR100) was isolated from a Korean rice paddy soil and was further tested for its sensitivity against eight commercial antibiotics. Based on morphological, biochemical, and molecular characteristics, this bacterium showed greatest similarity to members of the order Burkholderiales and was shown to be most closely related to members of the Burkholderia cepacia group. Strain KR100 hydrolyzed CM to 3,5,6-trichloro-2-pyridinol (TCP) and utilized TCP as the sole source of carbon for its growth. The isolate was also able to degrade chlorpyrifos, dimethoate, fenitrothion, malathion, and monocrotophos at 300 microg/ml but diazinon, dicrotophos, parathion, and parathion-methyl at 100 microg/ml. The ability to degrade CM was found to be encoded on a single plasmid of approximately 50 kb, pKR1. Genes encoding resistance to amphotericin B, polymixin B sulfate, and tetracycline were also located on the plasmid. This bacterium merits further study as a potential biological agent for the remediation of soil, water, or crop contaminated with organophosphorus compounds because of its greater biodegradation activity and its broad specificity against a range of organophosphorus insecticides.

Toxicity of cassia and cinnamon oil compounds and cinnamaldehyde-related compounds to Sitophilus oryzae (Coleoptera: Curculionidae).

The toxicity to adult Sitophilus oryzae (L.) (Coleoptera: Curculionidae) of two cassia oils (Especial and true), four cinnamon oils (technical, #500, bark, and green leaf), and (E)-cinnamaldehyde and its 41 structurally related compounds was examined by residual and vapor-phase toxicity bioassays. Results were compared with those of dichlorvos. In residual bioassays, cassia and cinnamon oils exhibited good insecticidal activity. Based on 48-h LD50 values, the toxicity of allyl cinnmate (0.0003 mg/cm2) was comparable with that of dichlorvos (0.00025 mg/cm2). Potent insecticidal activity also was observed with benzaldehyde, beta-caryophyllene, cinnamonitrile, hydrocinnamyl acetate, (E)-4-hydroxycinnamic acid, and alpha-terpineol (LD50 = 0.003-0.009 mg/cm2). Structure-activity relationships indicate that types of functional groups rather than hydrophobicity or vapor pressure parameters seem to play a role in determining the toxicities to adult S. oryzae. In vapor-phase toxicity tests with weevils, these compounds were more effective in closed containers than in open ones. These results indicate that the effect of the compounds was largely a result of action in the vapor phase. Cassia and cinnamon oils and test compounds described merit further study as potential fumigants for the control of S. oryzae because of their greater activity as a fumigant.

Selective growth-inhibiting effects of compounds identified in Tabebuia impetiginosa inner bark on human intestinal bacteria.

The growth-inhibiting activity of anthraquinone-2-carboxylic acid and lapachol identified in the inner bark of taheebo, Tabebuia impetiginosa, toward 10 human intestinal bacteria was evaluated by using a paper disk diffusion bioassay and compared to those of seven lapachol congeners (1,4-naphthoquinone, naphthazarin, menadione, lawsone, plumbagin, juglone, and dichlone) as well as two commercially available antibiotics, chloramphenicol and tetracycline. Anthraquinone-2-carboxylic acid exhibited very strong growth inhibition of Clostridium paraputrificum at 1 microg/disk while 100 microg/disk of lapachol was needed for moderate growth inhibition of the same organism. These two isolates exhibited weak inhibition of Clostridium perfringens and Escherichia coli at 100 microg/disk while no adverse effects were observed on the growth of Bifidobacterium adolescentis, Bifidobacterium bifidum, Bifidobacterium infantis, Lactobacillus acidophilus, and Lactobacillus casei at 1000 microg/disk. Structure-activity relationships indicate that a methyl group in the C-2 position of 1,4-naphthoquinone derivatives might play an important role in antibacterial activity.

Larvicidal activity and possible mode of action of four flavonoids and two fatty acids identified in Millettia pinnata seed toward three mosquito species.

BACKGROUND: Aedes aegypti and Aedes albopictus and Culex pipiens pallens mosquitoes transmit dengue fever and West Nile virus diseases, respectively. This study was conducted to determine the toxicity and mechanism of action of four flavonoids and two fatty acids from Millettia pinnata (Fabaceae) seed as well as six pure fatty acids and four fatty acid esters toward third instar larvae from insecticide-susceptible C. pipiens pallens and A. aegypti as well as wild A. albopictus. Efficacy of 12 experimental liquid formulations containing M. pinnata seed methanol extract and hydrodistillate (0.5-10.0% liquids) was also assessed. METHODS: The contact toxicities of all compounds and 12 formulations were compared with those of two larvicides, temephos and fenthion and the commercial temephos 200 g/L emulsifiable concentrate (EC). The possible mode of larvicidal action of the constituents was elucidated using biochemical methods. Larval mortality and cAMP level were analyzed by the Bonferroni multiple-comparison method. RESULTS: Potent toxicity was produced by karanjin, oleic acid, karanjachromene, linoleic acid, linolenic acid, pongamol, pongarotene, and elaidic acid toward C. pipiens pallens larvae (24 h LC50, 14.61-28.22 mg/L) and A. aegypti larvae (16.13-37.61 mg/L). Against wild A. albopictus larvae, oleic acid (LC50, 18.79 mg/L) and karanjin (35.26 mg/L) exhibited potent toxicity. All constituents were less toxic than either temephos or fenthion. Structure-activity relationship indicates that the degree of saturation, the side chain length, and the geometric isomerism of fatty acids appear to play a role in determining the fatty acid toxicity. Acetylcholinesterase (AChE) is the main site of action of the flavonoids, oleic acid, and palmitic acid. The mechanism of larvicidal action of elaidic acid, arachidic acid, and behenic acid might be due to interference with the octopaminergic system. Linoleic acid and linolenic acid might act on both AChE and octopaminergic receptor. M. pinnata seed extract or hydrodistillate applied as 10% liquid provided 100% mortality toward the three mosquito species larvae and the efficacy of the liquids was comparable to that of temephos 200 g/L EC. CONCLUSION: Further studies will warrant possible applications of M. pinnata seed-derived products as potential larvicides for the control of mosquito populations.

Toxicity of hiba oil constituents and spray formulations to American house dust mites and copra mites.

BACKGROUND: Dermatophagoides farinae and Tyrophagus putrescentiae are recognised as an important source of allergens. An assessment was made of the toxicity of hiba, Thujopsis dolabrata var. hondai, oil and 13 organic compounds and the control efficacy of four experimental spray formulations containing the oil (5-30 g L(-1) spray) against both mite species. RESULTS: In a contact + fumigant mortality bioassay, (-)-thujopsene was the most toxic constituent against D. farinae and T. putrescentiae (24 h LC50 9.82 and 10.92 µg cm(-2)), and the toxicity of the compound was nearly identical to that of benzyl benzoate (9.33 and 10.14 µg cm(-2)). The toxicity was more pronounced in carvacrol, (+)-terpinen-4-ol, ß-thujaplicin, (-)-terpinen-4-ol, cedrol and α-terpineol (LC50 12.05-15.20 and 12.74-16.48 µg cm(-2)) than in N,N-diethyl-3-methylbenzamide (LC50 35.53 and 38.42 µg cm(-2)) against both mite species. The hiba oil 30 g L(-1) spray and commercial permethrin (cis:trans 25:75) 2.5 g L(-1) spray treatment resulted in 100 and 11% mortality against the two mite species respectively. In vapour-phase mortality tests, the two compounds were consistently more toxic in closed versus open containers, indicating that toxicity was achieved mainly through the action of vapour. CONCLUSION: Reasonable mite control in indoor environments can be achieved by a spray formulation containing the 30 g L(-1) hiba oil as a potential contact-action fumigant.

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.

Larvicidal activity against Plutella xylostella of cordycepin from the fruiting body of Cordyceps militaris.

The insecticidal activities of methanol extracts of Cordyceps militaris Link (Ascomycotina: Clavicipitaceae) cultured on fresh pupae of Bombyx mori L against 3rd-instar larvae of Plutella xylostella L were examined using direct contact application. The larvicidal activity was more pronounced in an extract of C militaris fruiting body than in an extract of the pupae separated from the culture. The biologically active constituent of the Cordyceps fruiting body was characterized as cordycepin (3'-deoxyadenosine) by spectroscopic analysis. Responses varied according to dose, exposure time and application method. In a leaf-dipping test, cordycepin at 500 mg litre-1 caused no mortality at 1 DAT (day after treatment) but 78 and 100% mortality at 2 and 4 DAT, respectively, whereas 34 and 88% mortality at 3 and 5 DAT, respectively was observed at 300 mg litre-1. Cordycepin caused body colour change from pale green to dark brown and eventually body lysis. These results suggested that the larvicidal action may be attributable to a direct effect rather than an inhibitory action on chitin synthesis. There was a significant difference in insecticidal activity of cordycepin between leaf dipping (500 mg litre-1) with 100% mortality and topical application (10 micrograms per larva) with 0% mortality, suggesting that cordycepin has stomach action. Cordycepin merits further study as a potential P xylostella control agent or as a lead compound.

Contact and fumigant toxicity of Pinus densiflora needle hydrodistillate constituents and related compounds and efficacy of spray formulations containing the oil to Dermatophagoides farinae.

BACKGROUND: The toxicity of red pine needle hydrodistillate (RPN-HD), 19 RPN-HD constituents and another 12 structurally related compounds and the control efficacy of four experimental spray formulations containing RPN-HD (0.5. 1, 2 and 3% sprays) to adult Dermatophagoides farinae were evaluated. RESULTS: RPN-HD (24 h LC50 , 68.33 µg cm(-2) ) was toxic to mites. Menthol was the most toxic compound (12.69 µg cm(-2) ), and the toxicity of this compound and benzyl benzoate did not differ significantly. High toxicity was also produced by α-terpineol, bornyl acetate, geranyl acetate, thymol, linalyl acetate, terpinyl acetate, citral, linalool and camphor (18.79-36.51 µg cm(-2) ). These compounds were more toxic than either deet or dibutyl phthalate. In vapour-phase mortality tests, these compounds were consistently more toxic in closed versus open containers, indicating that their mode of delivery was largely a result of vapour action. RPN-HD 3% experimental spray provided 95% mortality against adult D. farinae, whereas permethrin (cis:trans, 25:75) 2.5 g L(-1) spray treatment resulted in 0% mortality. CONCLUSION: In the light of global efforts to reduce the level of highly toxic synthetic acaricides in indoor environments, RPN-HD and the compounds described merit further study as potential biocides for the control of Dermatophagoides populations as fumigants with contact action.