Fumigation Tests Research Articles

Composition of Essential Oils Extracted from Six Aromatic Plants of Kabylian Origin (Algeria) and Evaluation of Their Bioactivity onCallosobruchus maculatus(Fabricius, 1775) (Coleoptera: Bruchidae)

The essential oils extracted from six plants from Kabylia (Algeria), namely Eucalyptus globulus, Eucalyptus radiata, Myrtus communis, Salvia officinalis, Laurus nobilis and Pistacia lentiscus, were analysed by gas chromatography (GC/MS). Their biological activity was assessed on a pest destructive of stored products, Callosobruchus maculatus on cowpea (Vigna unguicultata). The results showed that these oils have two monoterpene compounds in common: α-pinene and β-pinene in different proportions. The bio-tests were conducted through contact, fumigation and repellency, under laboratory conditions. All the oils tested proved to be active, and the most significant action was the inhibition of oviposition during the tests through contact at a dose of 12µ1/50 g of bean seed. The essential oil of E. globulus caused 50% mortality in adult C. maculatus at 24 hours at a dose of 4µl/1 of air in fumigation tests. In addition, the essential oils tested were highly repellent towards adult C. maculatus at a dose of 16 µl.

Bioactivity of Pelargonium graveolens essential oil and related monoterpenoids against sweet potato whitefly, Bemisia tabaci biotype B

The sweet potato whitefly, Bemisia tabaci Gennadius biotype B (Hemiptera: Aleyrodidae), causes high economic losses in vegetables, beans, soybeans, peanuts, cotton, and several ornamental plants. Repeated spray applications of synthetic pesticides has led B. tabaci to develop resistance to numerous conventional insecticides, besides polluting the environment. In this work, we investigated the bioactivity of the essential oil of Pelargonium graveolens L’Her (Geraniaceae) (PG-EO) and some related monoterpenes against the sweet potato whitefly Bemisia tabaci Gennadius biotype B (Homoptera: Aleyrodidae) in tomato. This oil significantly reduced the number of B. tabaci adults on tomato leaflets. The deterrence experiments showed similar results for PG-EO, geraniol, and citronellol; however, citronellol was more effective than PG-EO. In fumigation tests, the essential oil of P. graveolens caused 100 % mortality of adults of B. tabaci biotype B at concentrations from 0.5 μL L−1 in air. The vapor toxicity of geraniol, linalool, and citronellol, the main chemical constituents of the essential oil of P. graveolens (PG-EO), was similar to that of PG-EO. These results suggest that PG-EO and its related monoterpenes are potentially applicable to develop effective natural product-based pest-management compounds.

Insecticidal properties of Pimpinella anisum essential oils against the Culex quinquefasciatus and the non-target organism Daphnia magna

The efficacy of an essential oil obtained from Pimpinella anisum fruits and its major compound, trans-Anethole, was tested on the eggs, larvae and adults of Culex quinquefasciatus. While causing no significant mortality on eggs, other tested stages were very sensitive to the essential oil and trans-Anethole. LC50 for the 2nd to 4th instar larvae was estimated as 26–27μL·L−1 and 15–19μL·L−1 for the essential oil and trans-Anethole, respectively. As for the essential oil applied on adults, LC(LD)50 was estimated as 9.3μLmL−1 (spray test), 1.9μLL−1 (fumigation test) and 0.6μgcm−2 (tarsal test), and for trans-Anethole as 8.1μLmL−1 (spray test), 2.1μLL−1 (fumigation test) and 0.4μgcm−2 (tarsal test). The time needed to achieve 50% mortality after application of LC(LD)99 of the essential oil was significantly different; for example, in larvicidal assays it ranged from 15 to 235min depending on the larval instar, and from 9 to 180min when applied to adults, depending on the mode of application. It was also found that temperature had an important effect on the larvicidal efficacy of the essential oil, and oviposition deterrent activity was studied.The essential oil and trans-Anethole were toxic for Daphnia magna (62–92% mortality) and significantly reduced its fertility at high concentrations (35–50μLmL−1) and long exposure (48h). However, no negative effect on Daphnia mortality or fertility was found at shorter exposure times (6h) and/or lower concentrations (20μLmL−1).Based on the results of this study, we can recommend the essential oil from P. anisum as a suitable active substance for potential botanical insecticides.

Antifungal, antiaflatoxigenic, and insecticidal efficacy of spearmint (Mentha spicata L.) essential oil

This study reports on the chemically characterized essential oil (EO) from Mentha spicata L. which was tested as a plant-based pesticide in because it showed efficacy against food-deteriorating molds, aflatoxin production, lipid peroxidation, and the insect pest Callosobruchus chinensis. The chemical characterization of this EO through GC/GC–MS analysis depicted 13 compounds comprising 97.09% of the EO, carvone being the major component (59.6%). The EO significantly inhibited growth and aflatoxin B1 production by the toxigenic strain of Aspergillus flavus [LHP(C)-D6] at 1.0 and 0.9 μl ml-1levels, respectively. The EO also had a broad fungitoxic effect against 19 food-deteriorating molds. The oil caused 100% mortality to C. chinensis during a fumigation test with an LC50 value of 0.003 μl ml−1 air after 24 h of treatment and 100% repellency at 0.025 μl ml−1 air concentration. The EO of M. spicata at 0.1 μl ml−1 air concentration was recorded as the effective fumigant, showing 98.46% oviposition deterrency, 100% ovicidal activity, 88.84% larvicidal activity, 72.91% pupaecidal activity, and 100% antifeedant activity against C. chinensis. The phytotoxicity assay showed 100% germination of EO-treated chickpea seeds. The EO had a low mammalian toxicity with an LD50 of 8342.33 μl kg−1 for oral toxicity on mice. The 50% inhibitory concentration (IC50) value of EO was 18.55 μl ml−1 during a DPPH (2, 2-diphenyl-1-picrylhydrazyl) assay.

Insecticidal, fumigant, and repellent activities of sweet wormwood oil and its individual components against red imported fire ant workers (Hymenoptera: Formicidae).

In total, 29 compounds from sweet wormwood ( Artemisia annua L.) oil were identified using gas chromatography–mass spectrometry. The five active components were d -camphor, linalool, cineole, α-terpineol, and l (−)-borneol. The effectiveness of A. annua oil, as well as d -camphor, linalool, cineole, α-terpineol, and l (−)-borneol, as fumigants, contact insecticides, and repellents, were tested on the red imported fire ant Solenopsis invicta Buren. The results indicated that A. annua oil has no significant topical toxicity; however, the spray contact test revealed that it has strong insecticidal activity and the inhibitory effect is stronger during closed exposure than during open exposure. In the fumigant test, cineole and d -camphor exhibited strong fumigant toxicity on minor and major S. invicta workers. They also caused 100% mortality at 5, 3, 2, and 1 mg/centrifuge tube but not at 0.5 mg/centrifuge tube. The mortality rates of linalool, α-terpineol, and l (−)-borneol exceeded 80% at 5, 3, and 2 mg/centrifuge tube. In the repellent test, cineole and d -camphor showed significant repellency at 100, 10, and 1 mg/kg. However, linalool, α-terpineol, and l (−)-borneol significantly facilitated digging at 10 and 1 mg/kg.

Low temperature phosphine fumigation for postharvest control of Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) on carnation

Phosphine (PH3) fumigation with different concentrations and exposure durations at low temperature was studied to determine its effects on Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) on carnations, and on postharvest quality. Laboratory tests showed that tolerance of L. huidobrensis to phosphine fumigation at 5°C varied with different life stages. 1 d-old eggs and adults showed the highest susceptibility, and 3d-old eggs was the most tolerant stage. In the fumigation tests of 3d-old eggs with a range of phosphine concentrations from 0.46 to 2.73mgL−1 and exposure durations from 6 to 144h at 5°C, 85.96–282.08h fumigation durations were required to achieve 99% mortality with different phosphine concentrations. The expression of C0.77T=k was obtained, which indicated that exposure duration other than phosphine concentration was the critical factor in the toxicity of phosphine against the 3d-old eggs of L. huidobrensis. Controlled atmosphere (CA) treatment with increased CO2 and reduced O2 had synergistic effects on phosphine toxicity. Phosphine fumigation could achieve 100% mortality for insects of L. huidobrensis on carnation, and had no significant adverse effects on vase life and damage indices of carnation at 1.92mgL−1 PH3 and 8% CO2 for 32h, and at 3.44mgL−1 for 3d at 5°C. All results suggested that phosphine fumigation at low temperature could be used as an alternative for postharvest control of L. huidobrensis on carnations.

Repellency and fumigant toxicity of clove and sesame oils against American cockroach (Periplaneta americana (L.)

Repellency and fumigant toxicity of clove ( Syzygium aromaticum ) and sesame ( Sesamum indicum ) oils were investigated against American cockroach ( Periplaneta americana (L.) in the laboratory of the Department of Biological Sciences, Faculty of Science, King Abdulaziz University, Jeddah Province, Saudi Arabia at 25 ± 3°C and 75 ± 5% relative humidity. Both clove and sesame oils showed variable percentages of repellency according to concentrations, exposure periods and stages. Clove oil exhibited strong repellent activity than sesame oil. First nymph was more sensitive than the fourth one followed by adults. After 48 h of exposure, complete repellency (100%) was recorded against first nymph at concentration of 2% for clove oil and 6% for sesame oil. Same result was obtained against fourth nymph at concentration of 10% of sesame oil after 48 h. While clove oil completely repelled all fourth nymphs after 24 h at concentration of 8%. For adult stage, the greatest repellency percentages were recorded by clove oil (90.00 ± 5.77%) and sesame oil (83.33 ± 3.33%) after 48 h at a concentration of 10%. Regarding the fumigant toxicity, clove oil provided highly significant effects against nymphs and adults of P. americana after 24 and 48 h, respectively. Complete mortality (100%) was recorded at a concentration of 7.5 μl/L of air for first nymph, 10 μl for fourth one and 17.5 μl for adults after 48 h of fumigation. First nymph was the most sensitive to clove oil by LC 50 value 1.06 μl followed by 3.12 μl for fourth nymph and 8.20 μl for adults. The fumigant tests showed that sesame oil did not exhibit toxicity against P. americana at concentrations range of 5 to 20 μl/L of air. In conclusion, both clove and sesame oils can be used as repellent botanical insecticides, but only clove oil can be used as fumigant agent against P. americana because sesame oil gave no effect at tested concentrations. Keywords : Sesame oil, clove oil, American cockroach, repellency, fumigant toxicity African Journal of Biotechnology Vol. 12(9), pp. 963-970

Ethnobotanicals for Storage Pest Management: Effect of powdered leaves of Olax zeylanica in suppressing infestations of rice weevil Sitophilus oryzae (Coleoptera: Curculionidae)

The rice weevil Sitophilus oryzae is considered the major problem in stored rice in Sri Lanka. Due to the adverse effects of pesticide usage, research on the re-evaluation and use of many ethnobotanicals as alternative storage pest control agents has been intensified. Although plant materials with insecticidal properties provide small-scale farmers with a locally available, eco-friendly and inexpensive method of control of storage insect pests, lack of understanding and knowledge prevent their widespread application. The present study was therefore undertaken to investigate the effectiveness of the botanical Olax zeylanica in controlling infestations of the rice weevil with the view of fulfilling this lack. In two separate bioassays, contact/feeding and fumigant toxicity of powdered leaves of O. zeylanica were tested against 1-7 days old adults under laboratory conditions. All experiments were conducted using a no-choice bioassay apparatus. Contact/feeding toxicity was tested by directly exposing weevils to 1.0, 3.0, 5.0 and 7.5g of leaf powder mixed with 100g of rice grains while fumigant toxicity was evaluated by using the same doses where weevils were exposed to fumes emitted from the leaf powders. In both bioassays 100% mortality of the weevils was observed within 18 hours of exposure to 3.0, 5.0 and 7.5g doses of leaf powder. Percentage weevil mortality in treated rice tested with three doses of leaf powder at all the time intervals (except for 1.0g) was significantly higher (p < 0.05) than that of the corresponding control. No Contact/feeding toxicity was recorded when weevils were directly exposed to 1.0g leaf powder whereas only 14% weevil mortality was observed even after 24hours of exposure to fumes of leaf powder. Results also revealed that weevil mortality increased both with increasing dose and time of exposure. It is of interest to note that in both bioassays a 100% weevil mortality was obtained after 18 hours of exposure to a lower amount of leaf powder such as 3.0g, when the adults were either directly exposed to the leaf powder or to its fumes. Moreover, LD50 values of 2.55g and 2.08g for leaf powders obtained after 12 hours of exposure to insects in contact/feeding toxicity test and fumigation test respectively indicated that leaf powder is more toxic to weevils when they were in direct contact with it. Findings of the present study bears out the exceptionally high efficacy of O. zeylanica leaves applied directly mixed with the food material or introduced as a fumigant to suppress weevil infestations in stored grains and strengthen the possibility of using this plant as an alternative to synthetic chemicals in storage pest management. Keywords: Olax zeylanica, Sitophilus oryzae, Direct Contact/Feeding Toxicity, Direct Fumigation Toxicity

Insecticidal activity of Ageratum conyzoides L., Coleus aromaticus Benth. and Hyptis suaveolens (L.) Poit essential oils as fumigant against storage grain insect Tribolium castaneum Herbst.

Essential oils (EOs) from Ageratum conyzoides L., Coleus aromaticus Benth. and Hyptis suaveolens (L.) Poit were extracted and tested against Tribolium castaneum Herbst, the storage grain insect. The EOs were found effective against Tribolium castaneum during in vitro as well as in vivo fumigant testing. The EOs of H. suaveolens and A. conyzoides showed 100% mortality of test insect at 250ppm while C. aromaticus at 350ppm. During in vivo fumigant testing of wheat samples against Tribolium castaneum, the essential oils of A. conyzoides and C. aromaticus completely checked the damage of wheat grains by the insect at 1000ppm while essential oil of H. suaveolens checked the grain damage completely even at 500ppm concentration. There was no adverse effect on seed germination as well as on seedling growth of EOs treated seeds showing non-phytotoxic nature of the oils. Hence, these EOs may be recommended as botanical insecticide against insect invasion of stored food commodities, thereby enhancing their shelf life.

Acaricidal activity and repellency of essential oil from Piper aduncum and its components against Tetranychus urticae

The chemical composition of essential oil of leaves of Piper aduncum L., growing wild in a fragment of the Atlantic Rainforest biome in northeastern Brazil, was determined through gas chromatography-mass spectrometry. The acaricidal activity and repellency of the essential oil and its components [dillapiole (0.28 g/ml), α-humulene (0.016 g/ml), (E)-nerolidol (0.0007 g/ml) and β-caryophyllene (0.0021 g/ml)] were evaluated in the laboratory against adults of Tetranychus urticae Koch. The mites were more susceptible to the oil in fumigation tests (LC(50) = 0.01 μl/l of air) than in contact test with closed Petri dish (LC(50) = 7.17 μl/ml); mortality was reduced by approximately 50 % in the latter test. The repellent action of the oil and toxicity by fumigation and contact did not differ significantly from the positive control (eugenol). The repellent activity was attributed to the components (E)-nerolidol, α-humulene and β-caryophyllene, whereas toxicity by fumigation and contact was attributed to β-caryophyllene. The effect of Piper oil and the role of its components regarding host plant preference with a two-choice leaf disk test are also discussed.

Bioactivity of tea tree oil from Melaleuca alternifolia against sheep lice (Bovicola ovis Schrank) in vitro

Tea tree oil (TTO) from the Australian native plant Melaleuca alternifolia has wide ranging bio-active properties, including insecticidal and repellent activity against arthropods. Furthermore, composition of commercially available Australian TTO is specified under an International Organization for Standardization standard (ISO 4730), reducing the potential for variable effects often noted with botanical pesticides. The effect of TTO, meeting the ISO standard for terpinen-4-ol chemotype, was tested against sheep lice (Bovicola ovis Schrank) in a series of laboratory studies. Immersion of wool for 60s in formulations containing concentrations of 1% TTO and above caused 100% mortality of adult lice and eggs. Exposure to vapours from TTO, delivered as droplets in fumigation chambers and when applied to wool also caused high mortality in both lice and eggs. The main active component of TTO in the fumigant tests was terpinen-4-ol. Treated surface assays and tests with wool where the formulation was allowed to dry before exposure of lice indicated low persistence. These studies demonstrate that TTO is highly toxic to sheep lice and active at concentrations that suggest potential for the development of TTO-based ovine lousicides.

Towards new botanical pesticides: the toxic effect of Eremanthus goyazensis (Asteraceae) leaves essential oil against Brevipalpus phoenicis (Acari: Tenuipalpidae)

This work reports the chemical characterization of Eremanthus goyzensis essential oil and its toxic effect over Brevipalpus phoenicis. The essential oil displayed a major composition of sesquiterpenes (61.87%) including trans-caryophillene (26.81%) and germacrene-D (13.31%). The fumigation test indicated a promising bioactivity over adult B. phoenicis individuals at 24 h (2.03 μL/L of air) and 48 h (1.08 μL/L of air) of exposition. A brief discussion of essential oils composition and their singular role on the toxic effect over B. phoenicis is provided here. Our results may contribute to a new and profitable use of a species of Brazilian flora on agribusiness.

Essential Oil Composition and Acaricidal Activity of Schinus Terebinthifolius from Atlantic Forest of Pernambuco, Brazil against Tetranychus Urticae

The compositions of the essential oils from unripe (UFr) and ripe (RFr) fruits of Schinus terebinthifolius were analyzed by GC and GC/MS. The major compound identified in both oils was limonene (UFr = 44.1 +/- 1.3%; RFr = 31.8 +/- 1.2%), followed by alpha-phellandrene (15.7 +/- 0.4%) in the UFr oil and thujene (21.7 +/- 0.9%) in the RFr oil. Repellent and toxicity activities of the two oils were also evaluated, and the results compared with eugenol. The UFr oil was more active in the fumigation tests (LC50 = 1.46 microL/L of air), whereas the RFr oil was more active in the sealed dishes (SD) than open dishes (OD) contact assay (LC50 = 3.04 microL/cm2) and not significantly different from eugenol. Both oils exhibited significant repellent activity comparable with that of eugenol. The results suggest that the repellent activity of these oils in association with its toxicity could be a great advantage for the integrated management of T. urticae.

Composition and Biological Potential of Essential Oil from Thelechitonia trilobata Growing in South Africa

Thelechitonia trilobata is regarded as a troublesome weed that grows to form a dense blanket over the soil preventing the growth of other crops in farmland. Although the plant is regarded as a notorious, invasive plant, its chemical composition and biological potential have not been reported. The essential oil was isolated from the fresh leaves of T. trilobata using hydrodistillation. alpha-Pinene (21.6%), alpha-phellendrene (21.0%), limonene (12.8%) and germacrene D (7.5%) were the major constituents of the oil. The essential oil was screened against agricultural pests. The anti-tick properties were tested on Ripicephalus e. ervertsi found on sheep, while repellency, fumigation, and contact toxicity tests were carried out with maize weevils. Except for the contact toxicity test, all other bioassays gave positive results.

Bioactivity of short‐chain aliphatic ketones against adults of the granary weevil, Sitophilus granarius (L.)

The granary weevil, Sitophilus granarius (L.), is one of the most damaging pests of stored grains, causing severe quantitative and qualitative losses. Sustainable control means, alternative to the commonly used fumigants and broad-spectrum contact insecticides, are urgently needed owing to legislative limits, the development of resistant insect strains and increasing consumer demand for safe food. Short-chain aliphatic ketones, known to be emitted by cereal grains and previously identified as repellents to adult granary weevils, were evaluated for their ability to disrupt insect orientation towards wheat grains and as possible natural fumigants. In behavioural bioassays, 2-pentanone, 2-hexanone, 2-heptanone and 2,3-butanedione significantly reduced insect orientation towards odours of wheat grains, with 2-hexanone and 2-heptanone being the most active. In fumigation tests, all compounds were effective in killing weevil adults, but they performed differently according to chemical structure, speed of action and presence of wheat grains. In the presence of grains, the highest fumigant toxicity was shown by 2-pentanone (LC(50) = 8.4 ± 1.0 mg L(-1)) after 24 h exposure, and by 2-pentanone (LC(50) = 4.5 ± 0.3 mg L(-1)), 2-heptanone (LC(50) = 7.1 ± 0.3 mg L(-1) ) and 2-hexanone (LC(50) = 8.1 ± 0.6 mg L(-1)) 1 week after the treatment end. Short-chain aliphatic ketones have potential for applications in IPM programmes for the granary weevil because of their behaviour-altering activity and fumigant toxicity.

Insecticidal activities of essential oils from leaves of Laurus nobilis L. from Tunisia, Algeria and Morocco, and comparative chemical composition

Laurus nobilis essential oils from Tunisia, Algeria and Morocco were analyzed for their chemical composition and assessed for their repellent and toxic activities against two major stored product pests: Rhyzopertha dominica and Tribolium castaneum. The three oils showed quantitative rather than qualitative differences in their chemical compositions. 1,8-cineole, linalool and isovaleraldehyde, were identified as the major common compounds whereas, α-pinene, α-terpineol, eugenylmethylether, β-pinene, spathulenol and β-myrcene were also well represented in all three oils. Results showed that L. nobilis essential oils were repellant and toxic to adults of R. dominica and T. castaneum. Repellent and fumigant toxicities were highly dependent upon insect species and oil origin.In filter paper tests, L. nobilis essential oil from Morocco was more effective compared to Tunisian and Algerian oils. RD50 values were respectively 0.013 μl/cm2, 0.036 μl/cm2 and 0.033 μl/cm2 for R. dominica versus 0.045 μl/cm2, 0.139 μl/cm2 and 0.096 μl/cm2 for T. castaneum. Moreover, fumigant activity tests showed that both R. dominica and T. castaneum were more susceptible to L. nobilis essential oil from Morocco than that from Algeria or Tunisia. The corresponding LC50 values were respectively 68, 99 and 113 μl/l air for R. dominica against 172, 194 and 217 μl/l air for T. castaneum. Our work clearly vindicates interest in the efficacy of essential oils from plants of Mediterranean origin both as insecticides and repellents against stored product pests.

Avaliação de óleos essenciais de plantas aromáticas com atividade inseticida em Triatoma infestans (Klug, 1834) (Hemiptera: Reduviidae)

Chagas disease is a major public health problem in Latin America. This work aimed to evaluate the insecticide action of essential oils of Anacardium humile, Cymbopogon nardus, Ocimum basilicum and Eucalyptus urograndis on Triatoma infestans nymphs of third and fourth stages of development by topic action and steam pressure (fumigation). Two repetitions were performed at the topic test with five nymphs of third and fourth stages of development of T. infestans . It was applied 1µL of each concentration on the dorsal region of each nymph. Two-liter pots with sealing covers were used at the fumigation test. The essential oils of O. gratissimum and E. urograndis showed insecticidal activity against T. infestans and A. humile and C. nardus showed an average of 5 and 15% mortality, respectively. For the fumigation, only the E. urograndis oil had effect with 100% of mortality on T. infestans and for the other oils it was not observed any effect of the steam pressure. This paper describes for the first time the insecticidal action of E. urograndis in smoke canister to control bugs. The results are important to the search for new molecular models with insecticidal action in bugs which are resistant to synthetic insecticides.

Chemical composition and fumigant effect of essentialoil of Lippia sidoides Cham. and monoterpenes against Tenebrio molitor (L.) (coleoptera: tenebrionidae)

The chemical composition of Lippia sidoides essential oils obtained by hydrodistillation was characterized and quantified by GC/MS and their insecticidal activity by fumigation test was assayed against Tenebrio molitor. Moreover, the toxicity of monoterpenes carvacrol, 1,8-cineol and thymol were also evaluated when applied alone or in binary (1:1) or tertiary (1:1:1) mixture. The essential oil of L. sidoides has as major constituents carvacrol (31.68%), ρ-cymene (19.58%), 1,8-cineole (9.26%) and ϒ-terpinene (9.21%), from a 21 compounds identified, being 92.53% of total. Both compounds have insecticidal activity against T. molitor, being the degree of toxicity of carvacrol > 1,8-cineole > L. sidoides essential oil > thymol, and its respectively LC50 at 24h were 5.53; 5.71; 8.04 and 14.71 µL/L air. When the different mixture of carvacrol, 1,8-cineole and thymol was assayed against T. molitor, the synergism among them was observed. For the mixture of carvacrol:1,8-cineole LC50 was 5.34 µL/L air; carvacrol:thymol 7.67 µL/L air; 1,8-cineole:thymol 7.51 µL/L air and carvacrol:1,8-cineole:thymol 6.34 µL/L air. Mainly, the monoterpene thymol had a synergic effect, which increased the toxicity of carvacrol and 1,8-cineole, both in binary mixture like carvacrol:thymol and 1,8-cineole:thymol.

Fumigant Toxicity of some Essential Oils on Adults of some Stored-Product Pests

Plant materials with insecticidal properties have been traditionally used for generations in some parts of the world. In this study, fumigant toxicity of some essential oils extracted from Rosmarinus officinalis L., Mentha pulegium L., Zataria multiflora, and Citrus sinensis (L.) Osbeck var. hamlin on adults of stored-product pests, including Tribolium castaneum, Sitophilus granarius, Callosobruchus maculatus, and Plodia interpunctella were investigated. Pure essential oils were used in glass vials for the bioassay. LC50 values of Citrus sinensis var. hamlin against T. castaneum, S. granarius, and C. maculatus were 391.28, 367.75, and 223.48 µL L -1 air after 24 h, 362.40, 20.45, and 207.17 µL L -1 air after 48 h, respectively. Furthermore, LC50 values of the fumigant test of C. sinensis and M. pulegium essential oils against S. granarius were 0.038 and 367.75 µL L -1 air after 24 h, 0.025 and 320.45 µL L -1 air after 48 h, respectively. On the other hand, LC50 values of R. officinalis and Z. multiflora on P. interpunctella moths were 0.93 and 1.75 µL L -1 after 24 h. Results showed that among tested essential oils, C. sinensis var. hamlin had good fumigant toxicity on T. castaneum, S. granarius, and C. maculatus. In addition, M. pulegium essential oil was stronger than C. sinensis var. hamlin on S. granarius. Results also indicated that both Z. multiflora and R. officinalis had fumigant toxicity on P. interpunctella adults. In summary, results indicated that these essential oils have good fumigant toxicity on stored-product pests.

Vapor-Phase Toxicity of Derris scandens Benth.-Derived Constituents against Four Stored-Product Pests

The vapor-phase toxicity of Derris scandens Benth.-derived constituents was evaluated against four stored-product pests ( Callosobruchus chinensis L., Sitophilus oryzae L., Rhyzopertha dominica L., and Tribolium castaneum H.) using fumigation bioassays and compared to those of commonly used insecticides. The structures of all constituents of were characterized by spectroscopic analyses [nuclear magnetic resonance (NMR) and mass spectrometry]. The sensitivity of the test insect to compounds varied with exposure time, concentration, and insect species. Over 100% mortality after 24 h was achieved with the compounds osajin (2), scandinone (5), sphaerobioside (8), and genistein (9) against all of the test insects, while laxifolin (3) and lupalbigenin (4) showed 100% mortality after 72 h against T. csataneum and R. dominica . Scandenone (1), scandenin A (6), and scandenin (7) were less effective. Among the insects, C. chinensis , S. oryzae , and R. dominica were more susceptible to the treatments, whereas T. castaneum was less susceptible. The results of fumigation tests indicated that compounds from D. scandens whole plant extract are potential candidates to control stored-product pests.