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Joel R. Coats - One of the best experts on this subject based on the ideXlab platform.
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Menthol acts as a positive allosteric modulator on nematode levamisole sensitive nicotinic acetylcholine receptors
Elsevier, 2019Co-Authors: Shivani Choudhary, Joel R. Coats, Djordje S. Marjianović, Colin R. Wong, Xiaoyu Zhang, Melanie Abongwa, Saša M. Trailović, Richard J. Martin, Alan P. RobertsonAbstract:The ongoing and widespread emergence of resistance to the existing anti-nematodal pharmacopeia has made it imperative to develop new anthelminthic agents. Historically, plants have been important sources of therapeutic compounds and offer an alternative to synthetic drugs. Monoterpenoids are phytochemicals that have been shown to produce acute toxic effects in insects and nematodes. Previous studies have shown nicotinic acetylcholine receptors (nAChRs) to be possible targets for naturally occurring plant metabolites such as carvacrol and carveol. In this study we examined the effects of Monoterpenoid compounds on a levamisole sensitive nAChR from Oesophagostomum dentatum and a nicotine sensitive nAChR from Ascaris suum. We expressed the receptors in Xenopus laevis oocytes and used two-electrode voltage-clamp to characterize the effect of various compounds on these cys-loop receptors. At 100 μM the majority of these compounds acted as antagonists. Interestingly, further experiments revealed that both 0.1 μM and 10 μM menthol potentiated acetylcholine and levamisole responses in the levamisole sensitive receptor but not the nicotine sensitive receptor. We also investigated the effects of 0.1 μM menthol on the contractility of A. suum somatic muscle strips. Menthol produced significant potentiation of peak contractions at each concentration of acetylcholine. The positive allosteric modulatory effects of menthol in both in vivo and in vitro experiments suggests menthol as a promising candidate for combination therapy with cholinergic anthelmintics. Keywords: Menthol, Allosteric modulation, nAChR, Monoterpenoid, Nematod
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quantitative structure activity relationships of Monoterpenoid binding activities to the housefly gaba receptor
Pest Management Science, 2012Co-Authors: Fan Tong, Joel R. CoatsAbstract:BACKGROUND: Monoterpenoids are a large group of plant secondary metabolites. Many of these naturally occurring compounds have shown good insecticidal potency on pest insects. Previous studies in this laboratory have indicated that some Monoterpenoids have positive modulatory effects on insect GABA receptors. In this study, the key properties of Monoterpenoids involved in Monoterpenoid binding activity at the housefly GABA receptor were determined by developing quantitative structure-activity relationship (QSAR) models, and the relationship between the toxicities of these Monoterpenoids and their GABA receptor binding activities was evaluated. RESULTS: Two QSAR models were determined for nine Monoterpenoids showing significant effects on [ 3 H]-TBOB binding and for ninep-menthane analogs with at least one oxygen atom attached to the ring. The Mulliken charges on certain carbon atoms, the log P value and the total energy showed significant relationships with binding activities to the housefly GABA receptor in these two QSAR models. CONCLUSIONS: From the QSAR models, some chemical and structural parameters, including the electronic properties, hydrophobicity and stability of Monoterpenoid molecules, were suggested to be strongly involved in binding activities to the housefly GABA receptor. These findings will help to understand the mode of action of these natural insecticides, and provide guidance to predict more Monoterpenoid insecticides. c � 2012 Society of Chemical Industry
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Quantitative structure–activity relationships of Monoterpenoid binding activities to the housefly GABA receptor
Pest management science, 2012Co-Authors: Fan Tong, Joel R. CoatsAbstract:BACKGROUND: Monoterpenoids are a large group of plant secondary metabolites. Many of these naturally occurring compounds have shown good insecticidal potency on pest insects. Previous studies in this laboratory have indicated that some Monoterpenoids have positive modulatory effects on insect GABA receptors. In this study, the key properties of Monoterpenoids involved in Monoterpenoid binding activity at the housefly GABA receptor were determined by developing quantitative structure-activity relationship (QSAR) models, and the relationship between the toxicities of these Monoterpenoids and their GABA receptor binding activities was evaluated. RESULTS: Two QSAR models were determined for nine Monoterpenoids showing significant effects on [ 3 H]-TBOB binding and for ninep-menthane analogs with at least one oxygen atom attached to the ring. The Mulliken charges on certain carbon atoms, the log P value and the total energy showed significant relationships with binding activities to the housefly GABA receptor in these two QSAR models. CONCLUSIONS: From the QSAR models, some chemical and structural parameters, including the electronic properties, hydrophobicity and stability of Monoterpenoid molecules, were suggested to be strongly involved in binding activities to the housefly GABA receptor. These findings will help to understand the mode of action of these natural insecticides, and provide guidance to predict more Monoterpenoid insecticides. c � 2012 Society of Chemical Industry
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Fumigation toxicity of Monoterpenoids to several stored product insects
Journal of Stored Products Research, 2003Co-Authors: Sangkyun Lee, Chris J Peterson, Joel R. CoatsAbstract:Abstract Twenty naturally occurring Monoterpenoids were evaluated in a preliminary fumigation screening test on some important stored-product pest insects, including the rice weevil, Sitophilus oryzae , the red flour beetle, Tribolium castaneum , the sawtoothed grain beetle, Oryzaephilus surinamensis , the house fly, Musca domestica , and the German cockroach, Blattella germanica . Cineole, l -fenchone, and pulegone at 50 μg/ml air caused 100% mortality in all five species tested. Ketone compounds were generally more toxic than other Monoterpenoids. Three Monoterpenoids, the ketones pulegone, l -fenchone, and the aldehyde perillaldehyde, were selected for further study. They were effective against T. castaneum in the fumigation assay; however the toxicity was relatively low in comparison to dichlorvos. LC 50 values of these three Monoterpenoids tended to decrease at longer exposure times and higher temperatures. Inclusion of either maize kernels or house fly medium (HFM) increased LC 50 values, HFM more so than maize kernels. Monoterpenoids may be suitable as fumigants or vapor-phase insecticides because of their high volatility, fumigation efficacy, and their safety.
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QSAR evaluation of Monoterpenoids' insecticidal activity.
Journal of agricultural and food chemistry, 2002Co-Authors: Justin Adam Grodnitzky, Joel R. CoatsAbstract:Monoterpenoids are naturally occurring compounds that are found in higher-order plants. These compounds are secondary metabolites that seem to play no major role in the metabolic functioning of the plants. One role of Monoterpenoids in the plants is to defend against plant-directed pathogens, herbivores, or competing plant species. These compounds are good leads for synthesis or isolation of more effective insecticides. To accomplish these goals, we developed quantitative structure-activity relationships (QSARs) in order to predict insect toxicity of Monoterpenoids and derivatives that have not yet been synthesized or experimentally tested. Correlations were found between toxicity and certain quantum and traditional chemical parameters. We found a linear relationship between LD(50) values for house fly toxicity and Mulliken populations in aromatic Monoterpenoids. Multiple linear regression of an E-State descriptor and a GETAWAY (GEometry, Topology and Atomic Weights AssemblY) descriptor also showed a relationship with house fly toxicity for a wide range of Monoterpenoids.
Christian Ulrichs - One of the best experts on this subject based on the ideXlab platform.
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direct and admixture toxicity of diatomaceous earth and Monoterpenoids against the storage pests callosobruchusmaculatus f and sitophilus oryzae l
Journal of Pest Science, 2010Co-Authors: Md Saiful Islam, Md Mahbub Hasan, Tanja Muchapelzer, Inga Mewis, Christian UlrichsAbstract:We investigated the effects of two commercial diatomaceous earth based insecticides (DE), Protect-It® and SilicoSec®, the nano-structured silica product AL06, developed by the section for Urban Plant Ecophysiology at Humboldt University Berlin, and the Monoterpenoids, eugenol, and cinnamaldehyde on two stored product pests, Callosobruchus maculatus and Sitophilus oryzae. Protect-It® was more effective than SilicoSec® against C. maculatus while the reverse was true for S. oryzae. Generally C. maculatus was more sensitive towards DE and silica treatment than S. oryzae. Mortality rate of both pest species increased when DE’s were applied to food commodities previously treated with a Monoterpenoid. In admixture experiments, the toxicity of SilicoSec® + cinnamaldehyde (LD50 = 42.73 ppm), SilicoSec® + eugenol (LD50 = 24.30 ppm), and Protect-It® + eugenol (LD50 = 2.60 ppm) was increased over DE alone against S. oryzae. Both substances showed a synergistic effect considering their co-toxicity coefficient relative to the LD50-value. In contrast, we could not find any synergistic effects in experiments with C. maculatus. Here only Protect-It® + cinnamaldehyde (LD50 = 20.84 ppm) showed an additive effect while all other combinations of Monoterpenoid and DE indicated antagonistic effects. In addition to contact insecticidal effects both Monoterpenoids showed a strong fumigant action. The presented results indicate that the natural product DE has great potential to replace synthetic pesticides commonly used in stored product pest management. Efficacy of DE can be improved by adding certain Monoterpenoids against certain insect pests.
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direct and admixture toxicity of diatomaceous earth and Monoterpenoids against the storage pests callosobruchusmaculatus f and sitophilus oryzae l
Journal of Pest Science, 2010Co-Authors: Md Saiful Islam, Md Mahbub Hasan, Tanja Muchapelzer, Inga Mewis, Chaoliang Lei, Christian UlrichsAbstract:We investigated the effects of two commercial diatomaceous earth based insecticides (DE), Protect-It® and SilicoSec®, the nano-structured silica product AL06, developed by the section for Urban Plant Ecophysiology at Humboldt University Berlin, and the Monoterpenoids, eugenol, and cinnamaldehyde on two stored product pests, Callosobruchus maculatus and Sitophilus oryzae. Protect-It® was more effective than SilicoSec® against C. maculatus while the reverse was true for S. oryzae. Generally C. maculatus was more sensitive towards DE and silica treatment than S. oryzae. Mortality rate of both pest species increased when DE’s were applied to food commodities previously treated with a Monoterpenoid. In admixture experiments, the toxicity of SilicoSec® + cinnamaldehyde (LD50 = 42.73 ppm), SilicoSec® + eugenol (LD50 = 24.30 ppm), and Protect-It® + eugenol (LD50 = 2.60 ppm) was increased over DE alone against S. oryzae. Both substances showed a synergistic effect considering their co-toxicity coefficient relative to the LD50-value. In contrast, we could not find any synergistic effects in experiments with C. maculatus. Here only Protect-It® + cinnamaldehyde (LD50 = 20.84 ppm) showed an additive effect while all other combinations of Monoterpenoid and DE indicated antagonistic effects. In addition to contact insecticidal effects both Monoterpenoids showed a strong fumigant action. The presented results indicate that the natural product DE has great potential to replace synthetic pesticides commonly used in stored product pest management. Efficacy of DE can be improved by adding certain Monoterpenoids against certain insect pests.
Ülo Niinemets - One of the best experts on this subject based on the ideXlab platform.
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regulation of floral terpenoid emission and biosynthesis in sweet basil ocimum basilicum
Journal of Plant Growth Regulation, 2016Co-Authors: Yifan Jiang, Ülo NiinemetsAbstract:Past studies have focused on the composition of essential oil of Ocimum basilicum leaves, but data on composition and regulation of its aerial emissions, especially floral volatile emissions, are scarce. We studied the chemical profile, within-flower spatial distribution (sepals, petals, pistils with stamina, and pedicels), diurnal emission kinetics and effects of exogenous methyl jasmonate (MeJA) application on the emission of floral volatiles by dynamic headspace collection, and identification using gas chromatography-mass spectrometry (GC–MS) and proton-transfer reaction mass spectrometry. We observed more abundant floral emissions from flowers compared with leaves. Sepals were the main emitters of floral volatiles among the flower parts studied. The emissions of lipoxygenase compounds and Monoterpenoids, but not sesquiterpene emissions, displayed a diurnal variation driven by light. Response to exogenous MeJA treatment of flowers consisted of a rapid stress response and a longer-term acclimation response. The initial response was associated with enhanced emissions of fatty acid derivatives, Monoterpenoids, and sesquiterpenoids without variation of the composition of individual compounds. The longer-term response was associated with enhanced Monoterpenoid and sesquiterpenoid emissions with profound changes in the emission spectrum. According to correlated patterns of terpenoid emission changes upon stress, highlighted by a hierarchical cluster analysis, candidate terpenoid synthases responsible for observed diversity and complexity of released terpenoid blends were postulated. We conclude that flower volatile emissions differ quantitatively and qualitatively from leaf emissions, and overall contribute importantly to O. basilicum flavor, especially under stress conditions.
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A model analysis of the effects of nonspecific Monoterpenoid storage in leaf tissues on emission kinetics and composition in Mediterranean sclerophyllous Quercus species
Global Biogeochemical Cycles, 2002Co-Authors: Ülo Niinemets, Markus ReichsteinAbstract:[1] Although Monoterpenoid-emitting Quercus species lack specific terpene storage structures, they may store Monoterpenoids in nonspecific leaf compartments. To determine whether such storage may influence emission responses to diurnal changes in environmental factors, a dynamic emission model including “fast” and “slow” storage pools in parallel was constructed. Existence of two storage pools was inferred from the circumstance that monoterpene efflux from darkened leaves was poorly described by single-exponential decay relationship, but was well parameterized by double exponentials. Simulations indicated that nonspecific terpenoid storage may significantly alter daily Monoterpenoid emission both at leaf and canopy scales. The model also described shifts in fractional Monoterpenoid composition after changes in environmental factors that cannot be explained by current algorithms. Time constants for the “fast” pool were negatively associated with Monoterpenoid equilibrium gas/water partition coefficient (H), suggesting that the “fast” pool is in leaf liquid phase. The time constants for the “slow” pool were independent of H, but scaled positively with Monoterpenoid octanol/water partition coefficient, indicating that this pool is in lipid phase. Based on tentative pool locations and Monoterpenoid physico-chemical characteristics, time constants of various pools were computed using a flow/conductance model. Although the time constants were correlated, the theoretical estimates were larger than those derived empirically. Nonhomogeneous Monoterpenoid distribution, aggregation within leaf liquid phase, and adsorption to apoplast surfaces that all decrease the area for diffusion and decrease the effective diffusion coefficients likely explain this discrepancy. We conclude that physico-chemical models are needed to parameterize nonspecific storage effects on monoterpene emission dynamics and emission composition.
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Stomatal Constraints May Affect Emission of Oxygenated Monoterpenoids from the Foliage of Pinus pinea
Plant physiology, 2002Co-Authors: Ülo Niinemets, Markus Reichstein, Michael Staudt, G. Seufert, John TenhunenAbstract:Dependence of Monoterpenoid emission and fractional composition on stomatal conductance ( G V ) was studied in Mediterranean conifer Pinus pinea , which primarily emits limonene and trans-β-ocimene but also large fractions of oxygenated Monoterpenoids linalool and 1,8-cineole. Strong decreases in G V attributable to diurnal water stress were accompanied by a significant reduction in total Monoterpenoid emission rate in midday. However, various Monoterpenoids responded differently to the reduction in G V , with the emission rates of limonene and trans-β-ocimene being unaffected but those of linalool and 1,8-cineole closely following diurnal variability in G V . A dynamic emission model indicated that stomatal sensitivity of emissions was associated with Monoterpenoid Henry9s law constant ( H , gas/liquid phase partition coefficient). Monoterpenoids with a large H such as trans-β-ocimene sustain higher intercellular partial pressure for a certain liquid phase concentration, and stomatal closure is balanced by a nearly immediate increase in monoterpene diffusion gradient from intercellular air-space to ambient air. The partial pressure rises also in compounds with a low H , but more than 1,000-fold higher liquid phase concentrations of linalool and 1,8-cineole are necessary to increase intercellular partial pressure high enough to balance stomatal closure. The system response is accordingly slower, and the emission rates may be transiently suppressed by low G V . Simulations further suggested that linalool and 1,8-cineole synthesis rates also decreased with decreasing G V , possibly as the result of selective inhibition of various monoterpene synthases by stomata. We conclude that physicochemical characteristics of volatiles not only affect total emission but also alter the fractional composition of emitted Monoterpenoids.
Md Saiful Islam - One of the best experts on this subject based on the ideXlab platform.
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direct and admixture toxicity of diatomaceous earth and Monoterpenoids against the storage pests callosobruchusmaculatus f and sitophilus oryzae l
Journal of Pest Science, 2010Co-Authors: Md Saiful Islam, Md Mahbub Hasan, Tanja Muchapelzer, Inga Mewis, Christian UlrichsAbstract:We investigated the effects of two commercial diatomaceous earth based insecticides (DE), Protect-It® and SilicoSec®, the nano-structured silica product AL06, developed by the section for Urban Plant Ecophysiology at Humboldt University Berlin, and the Monoterpenoids, eugenol, and cinnamaldehyde on two stored product pests, Callosobruchus maculatus and Sitophilus oryzae. Protect-It® was more effective than SilicoSec® against C. maculatus while the reverse was true for S. oryzae. Generally C. maculatus was more sensitive towards DE and silica treatment than S. oryzae. Mortality rate of both pest species increased when DE’s were applied to food commodities previously treated with a Monoterpenoid. In admixture experiments, the toxicity of SilicoSec® + cinnamaldehyde (LD50 = 42.73 ppm), SilicoSec® + eugenol (LD50 = 24.30 ppm), and Protect-It® + eugenol (LD50 = 2.60 ppm) was increased over DE alone against S. oryzae. Both substances showed a synergistic effect considering their co-toxicity coefficient relative to the LD50-value. In contrast, we could not find any synergistic effects in experiments with C. maculatus. Here only Protect-It® + cinnamaldehyde (LD50 = 20.84 ppm) showed an additive effect while all other combinations of Monoterpenoid and DE indicated antagonistic effects. In addition to contact insecticidal effects both Monoterpenoids showed a strong fumigant action. The presented results indicate that the natural product DE has great potential to replace synthetic pesticides commonly used in stored product pest management. Efficacy of DE can be improved by adding certain Monoterpenoids against certain insect pests.
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direct and admixture toxicity of diatomaceous earth and Monoterpenoids against the storage pests callosobruchusmaculatus f and sitophilus oryzae l
Journal of Pest Science, 2010Co-Authors: Md Saiful Islam, Md Mahbub Hasan, Tanja Muchapelzer, Inga Mewis, Chaoliang Lei, Christian UlrichsAbstract:We investigated the effects of two commercial diatomaceous earth based insecticides (DE), Protect-It® and SilicoSec®, the nano-structured silica product AL06, developed by the section for Urban Plant Ecophysiology at Humboldt University Berlin, and the Monoterpenoids, eugenol, and cinnamaldehyde on two stored product pests, Callosobruchus maculatus and Sitophilus oryzae. Protect-It® was more effective than SilicoSec® against C. maculatus while the reverse was true for S. oryzae. Generally C. maculatus was more sensitive towards DE and silica treatment than S. oryzae. Mortality rate of both pest species increased when DE’s were applied to food commodities previously treated with a Monoterpenoid. In admixture experiments, the toxicity of SilicoSec® + cinnamaldehyde (LD50 = 42.73 ppm), SilicoSec® + eugenol (LD50 = 24.30 ppm), and Protect-It® + eugenol (LD50 = 2.60 ppm) was increased over DE alone against S. oryzae. Both substances showed a synergistic effect considering their co-toxicity coefficient relative to the LD50-value. In contrast, we could not find any synergistic effects in experiments with C. maculatus. Here only Protect-It® + cinnamaldehyde (LD50 = 20.84 ppm) showed an additive effect while all other combinations of Monoterpenoid and DE indicated antagonistic effects. In addition to contact insecticidal effects both Monoterpenoids showed a strong fumigant action. The presented results indicate that the natural product DE has great potential to replace synthetic pesticides commonly used in stored product pest management. Efficacy of DE can be improved by adding certain Monoterpenoids against certain insect pests.
Rong Tsao - One of the best experts on this subject based on the ideXlab platform.
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Antifungal activity of Monoterpenoids against postharvest pathogens Botrytis cinerea and Monilinia fructicola.
Journal of Essential Oil Research, 2000Co-Authors: Rong Tsao, Ting ZhouAbstract:Abstract Twenty two naturally occurring Monoterpenoid compounds were selected for antifungal evaluation against two of the most common postharvest pathogens on temperate fruits, Botrytis cinerea and Monilinia fructicola. Experiments were carried out in order to examine the separate effects of these compounds on spore germination and mycelial growth. The growth inhibition test was conducted by incorporating the compounds into the medium, or by exposing the fungi to the vapor of the Monoterpenoids. The results showed that carvacrol and thymol, the only two phenolic Monoterpenoids, were the most potent inhibitors to the two pathogens in the germination and growth inhibition tests. Both of the compounds completely prevented the spore germination and mycelial growth of B. cinerea and M. fructicola at 100 μg/mL. Even at 10 μg/mL medium (0.25 mg/petri dish) in the volatility test, carvacrol and thymol had 85% and 82% inhibition at 48 h against B. cinerea, and 38% and 57% against M. fructicola, respectively. Othe...
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influence of dietary applied Monoterpenoids and derivatives on survival and growth of the european corn borer lepidoptera pyralidae
Journal of Economic Entomology, 1999Co-Authors: Rong Tsao, Joel R. CoatsAbstract:Sixteen natural Monoterpenoids and 6 synthetic derivatives were selected for study of larvicidal activity and growth inhibitory effect against the European corn borer, Ostrinia nubilalis (Hubner). For this study, 2 different dietary exposure bioassays were used: compounds applied on the diet surface (on-diet), and compounds incorporated into the diet (in-diet). Most of the Monoterpenoid compounds showed some degree of larvicidal activity in both bioassay procedures after a 6-d exposure period. Among the Monoterpenoids, pulegone was the most active. Larvicidal toxicities were significantly enhanced for the structurally modified compounds; Monoterpenoid derivatives MTEE-25 (2-fluoroethyl thymyl ether) and MTEE-P (propargyl citronellate) were most toxic to borer larvae. When reared on diet containing the Monoterpenoids or their derivatives, changes in developmental parameters and pupal weights of the European corn borer also were noted when they were fed several of the compounds. Some larvae reared on treated diet with higher concentrations of the test compounds died before pupating. In general, growth and development of the European corn borer were affected by Monoterpenoid compounds, and some compounds such as l-menthol, pulegone, MTEE-25, and MTEE-P acted as insect growth inhibitors.
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insecticidal activity of Monoterpenoids to western corn rootworm coleoptera chrysomelidae twospotted spider mite acari tetranychidae and house fly diptera muscidae
Journal of Economic Entomology, 1997Co-Authors: Sangkyun Lee, Rong Tsao, Chris J Peterson, Joel R. CoatsAbstract:Acute toxicities of 34 naturally occurring Monoterpenoids were evaluated against 3 important arthropod pest species; the larva of the western corn rootworm, Diabrotica virgifera virgifera LeConte; the adult of the twospotted spider mite. Tetranychus urticae Koch; and the adult house fly. Musca domestica L. Potential larvicidal or acaricidal activities of each Monoterpenoid were determined by topical application, leaf-dip method, soil bioassay, and greenhouse pot tests. Phytotoxicity was also tested on a corn plant. Citronellic acid and thymol were the most topically toxic against the house fly, and citronellol and thujone were the most effective on the western corn rootworm. Most of the Monoterpenoids were lethal to the twospotted spider mite at high concentrations; carvomenthenol and terpinen-4-ol were especially effective. A wide range of Monoterpenoids showed some larvicidal activity against the western corn rootworm in the soil bioassay. Perillaldehyde, the most toxic (LC50 = 3 micrograms/g) in soil, was only 1/3 as toxic as carbofuran, a commercial soil insecticide (LC50 = 1 microgram/g). Selected Monoterpenoids also effectively protected corn roots from attack by the western corn rootworm larvae under greenhouse conditions. alpha-Terpineol was the best Monoterpenoid in the greenhouse pot test. The acute toxicity of Monoterpenoids was low relative to conventional insecticides. Some Monoterpenoids were phytotoxic to corn roots and leaves. l-Carvone was the most phytotoxic, whereas pulegone was the safest. The results with thymyl ethyl ether, one of the synthetic derivatives of thymol, showed a potential of derivatization to reduce Monoterpenoid phytotoxicity.
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insecticidal activity of Monoterpenoids to western corn rootworm coleoptera chrysomelidae twospotted spider mite acari tetranychidae and house fly diptera muscidae
Journal of Economic Entomology, 1997Co-Authors: Rong Tsao, Chris J Peterson, Joel R. CoatsAbstract:Acute toxicities of 34 naturally occurring Monoterpenoids were evahmt{'d against 3 important arthropod pest species; the larva of the western com rootworm, Diahrotica t:irgifl'rll eir'gifl'nl Lt'Conte; the adult of the twospotted spider mite, Tctrallyclllls urticac Koch; and the adult hOllse Ay, Musca domestica L. Potential larvicidal or acaricidal activities of each 111onoterpenoid were determined by topical application, leaf-dip method, soil hioassay, and greenhollse pot tests. Phytotoxicity was also tested on a com plant. Citronellic acid and thymol Wt're the most topically toxic against the house Ay, and citronellol and thujone were the most {'ff{'ctin' on tilt' western com rootworm. Most of the Monoterpenoids were ({'thai to th{' twospotted spider mite at high concentrations; carvomenthenol and terpinen-4-ol were {'s- pecially effective. A \\~de range of Monoterpenoids showed some larvicidal activity against the wl'stl'm com rootworm in the soil bioassay. Perillaldehyde, the most tmdc (LC:;o = 3 J.tWf!.)in soil, was on)y 1/3 as toxic as carbofman, a commercial soil insecticide (LC:;o = 1 J.tWg). Selected Monoterpenoids also effectively protected com roots from attack by the western com root- worm larvae under greenhouse conditions. lr- Terpineol was the best Monoterpenoid in til{' greenhollse pot test. The acute toxicity of Monoterpenoids was low relative to conventional insecticides. Some Monoterpenoids were phytotm';c to com roots and leaves. {-Carvone was the most phytotm';c, whereas pulegone was the safest. The results with thymy) ethyl dhl'r, Ollt' of the s)11tbetic derivatives of tllymol, showed a potential of derivatization to red lice Illonoterpenoid phytotoxicity.