Fumigant Toxicity Of Essential Oils Research Articles

Chemical composition and insecticidal activity of essential oil from Ziziphora clinopodioides Lam. used against the Mediterranean flour moth, Ephestia kuehniella Zeller

Abstract The Mediterranean flour moth, Ephestia kuehniella Zeller, is a major pest of stored grain products, particularly flour. There have been major concerns over the application of conventional insecticides in stored products, which have strongly demonstrated the need for applying such alternative safe compounds as essential oils. The aim of the present study is to investigate the chemical composition and fumigant toxicity of essential oil from Ziziphora clinopodioides Lam. against the eggs, larvae, and adults of E. kuehniella. All toxicity tests were carried out under laboratory conditions set at 26±1°C and 70% relative humidity (RH). The results of gas chromatography-mass spectrometry (GC/MS) analysis indicated that the essential oil extracted from the leaves of Z. clinopodioides, is rich in pulegone (49.4%), piperitenone (10.7%), menthone (8.9%), and 1,8-cineol (6.9%). Based on the bioassay results, the LC50 value of the tested oil was estimated to be 54.61 μl · l−1 air for larvae and 1.39 μl · l−1 air for adults. Also, it is shown that increasing the oil concentration resulted in a significant increase in oviposition deterrency as well as a considerable reduction in the egg hatching percentage. These results suggest that Z. clinopodioides oil could be a potential candidate as a fumigant for managing E. kuehniella in stored products.

Fumigant Toxicity of Essential Oils from Basil and Spearmint Against Two Major Pyralid Pests of Stored Products

The fumigant activity of essential oil vapors distilled from sweet basil Ocimum basilicum L. and spearmint Mentha spicata L. (Lamiaceae) were tested against two major stored products pests Ephestia kuehniella (Zeller) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae). Various oil doses (0.5, 2.5, 5, 50, 250, 500, 1,000, and 1,500 µl/liter air), for an exposure period of 24 h, were tested. The essential oils were subjected to gas chromatography-mass spectrometry analysis and revealed that the major compounds were for spearmint oil carvone (67.1%) and limonene (+1,8 cineole; 14.3%) and for basil oil linalool (45.9%), 1,8 cineole (16.7%) and eugenol (10.3%). Apart from a few exceptions, no significant differences in insecticidal action were observed between basil and spearmint oil. Both oils were highly effective against adult moths, given that notable mortality (>80%) was recorded after exposure to low doses such as 2.5 µl/liter. Noteworthy, egg mortality was also recorded, reaching 73-79% for basil and 56-60% for spearmint. Toxicity data indicated that larvae and pupae were the most tolerant stages in all cases. Larval mortality never exceeded 21 and 18%, for basil and spearmint, respectively, irrespective of moth species. Basil and spearmint oils displayed mortalities as high as 38 and 28% in pupae. Lethal doses (LD50 and LD99) values were estimated via probit analysis. Developmental stage proved to be a significant factor, whereas the effect of oil species on insect mortality was insignificant. With the exception of adult individuals, basil and spearmint oils did not show satisfactory overall insecticidal activity against E. kuehniella and P. interpunctella.

Repellent and Fumigant Activities of Tanacetum nubigenum Wallich. ex DC Essential Oils against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae).

The repellent and fumigant toxicity of essential oils of Tanacetum nubigenum Wallich. ex DC collected from three different habitats (Gothing, Burphu and Glacier) of Uttarakhand Himalayas, India named as TNG, TNB and TNM respectively, were investigated against the adults of red flour beetle Tribolium castaneum (Herbst). Among the three samples tested, TNG was found to more potent exhibiting more repellent effect towards the insects and with LC50 values by fumigant bioassay were 13.23 and 8.32 µl per 0.25 L air at 24 and 48 h exposure of insects to the essential oil respectively. In between other two oil samples, TNM was superior in potency showed LC50 value of 14.22 (24 h) & 8.82 µl per 0.25 L air (48 h). During in vivo study all the essential oil samples significantly protected 500 g of wheat grains for 6 months from insect infestation as compared to non fumigated grains and order of efficacy was TNG>TNM>TNB. There were no side effects of essential oils on germination rate of grains (<85%) exposed for 6 months after fumigation. The present study suggests that essential oil of T. nubigenum can be explored as novel natural fumigants for the control of stored product insects.

Chemical Composition and Acaricidal Effects of Essential Oils ofFoeniculum vulgareMill. (Apiales: Apiaceae) andLavandula angustifoliaMiller (Lamiales: Lamiaceae) againstTetranychus urticaeKoch (Acari: Tetranychidae)

Utilization of synthetic acaricides causes negative side-effects on nontarget organisms and environment and most of the mite species such as two spotted spider mite,Tetranychus urticaeKoch, are becoming resistant to these chemicals. In the present study, essential oils of fennel,Foeniculum vulgareMill., and lavender,Lavandula angustifoliaMiller, were hydrodistilled using Clevenger apparatus and chemical composition of these oils was analyzed by GC-MS. Anethole (46.73%), limonene (13.65%), andα-fenchone (8.27%) in the fennel essential oil and linalool (28.63%), 1,8-cineole (18.65%), and 1-borneol (15.94%) in the lavender essential oil were found as main components. Contact and fumigant toxicity of essential oils was assessed against adult females ofT. urticaeafter 24 h exposure time. The essential oils revealed strong toxicity in both contact and fumigant bioassays and the activity dependeds on essential oil concentrations. Lethal concentration 50% for the population of mite (LC50) was found as 0.557% (0.445–0.716) and 0.792% (0.598–1.091) in the contact toxicity and 1.876 μL/L air (1.786–1.982) and 1.971 μL/L air (1.628–2.478) in the fumigant toxicity for fennel and lavender oils, respectively. Results indicated thatF. vulgareandL. angustifoliaessential oils might be useful for managing of two spotted spider mite,T. urticae.

Chemical constituents and insecticidal activity of the essential oil from fruits of foeniculum vulgare miller on larvae of khapra beetle (trogoderma granarium everts)

Abstract The objective of current study was to determine the chemical constituents and fumigant toxicity of essential oil isolated by hydro-distillation from dry fruit of bitter fennel (Foeniculum vulgare Miller). The chemical composition of the essential oil was assessed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Constituents of the oil were determined as α-pinene (1.6%) and limonene (3.3%), fenchone (27.3%), estragol (3.9%), and (E)-anethole (61.1%). The fumigant toxicity of the essential oil was tested on larvae of the stored product insect Trogoderma granarium Everts. The mortality of larvae was tested at different concentrations ranging from 31.2 to 531.2 μl/l air and at different exposure times (24 and 48 h). Probit analysis showed that LC50 and LC90 following a 48 h-exposure period for essential oil were 38.4 and 84.6 μl/l, respectively. These results showed that the essential oil from F. vulgare may be applicable to the management of populations of stored-product insects.

Fumigant toxicity of Laurus nobilis and Myrtus communis essential oils on larvae and adults of the Red flour beetle, Tribolium castaneum Herbst (Col.: Tenebrionidae)

Considering the invasion to food commodities by insects and harmful effect of chemical pesticides, essential oils are among the best known substances tested against stored product pests. These compounds may act as fumigants, contact insecticides, repellents or anti-feedants. In present study, fumigant toxicity of essential oils from Laurus nobilis L. and Myrtus communis L. was assessed on larvae and adults of Tribolium castaneum Herbst at 27 ± 2 °C, 60 ± 5% RH in darkness. Each essential oil was tested in five concentrations with three replicates. The LC50 values of L. nobilis and M. communis against adults of beetle were calculated 243.78 and 56.11 μl/l and LC95 values for them were 685.85 and 144.01 μl/l, respectively. For the larvae of T. castaneum, the LC50 values for L. nobilis and M. communis were 211.64 and 69.63 and LC95 values were 656.84 and 183.65 μl/l, respectively. Results showed that these essential oils may have potential as botanical control agents against larvae and adults of T. castaneum.

Fumigant toxicity of essential oil from Tanacetum balsamita L. (Compositae) against adults and eggs of Callosobruchus maculatus F. (Coleoptera: Bruchidae)

The essential oil of Tanacetum balsamita L. was tested against Callosobruchus maculatus F. at the rates of 5.12, 7.23, 10.19, 14.36 and 20.24 μl/l air for adults and 5.3, 8.5, 10.8, 13.7 and 17.4 μl/l air for eggs. All experiments were conducted at 27 ± 1 °C and 65 ± 5% relative humidity. Mortality was counted after 24, 48 and 72 h of exposure and all adults (dead and alive) were taken out of the vials and the vials were left at the same conditions for further 35 days to assess progeny production. For mortality of eggs, unhatched eggs were counted after 7 days. The adults treated with oil were more susceptible than eggs. At highest dose (20.24 μl/l air) mortality of adults after 72 h, received 75.2%, but this amount for egg at 17.4 μl/l air after 72 h was 49.06%. The lowest LC50 value on 72 h was observed in adults (1.96 μl/l air). Also, the lowest LC95 value on 72 h was observed in adults (42.86 μl/l air). The percentage of reduced progeny on 72 h was 50.92% at 20.24 μl/l air. Our results suggest that T. balsamita can be used as an alternative to synthetic insecticides but higher dose may be needed.

Fumigant toxicity of essential oil of Mugwort (Artemisia vulgaris L.) against three major stored product beetles

Application of plants essential oil for the evaluation of their fumigant toxicity and insecticidal properties is the goal of many researches. In this study, aerial parts of Artemisia vulgaris L. were subjected to hydrodistillation using a Clevenger-type apparatus, and the chemical composition of the volatile oils was studied by gas chromatography–mass spectrometry. Alpha-Pinene (23.56) was the main component of the essential oil. Insecticidal activity of the oil was evaluated against Tribolium castaneum (Herbst), Callosobruchus maculatus (F.) and Rhizopertha dominica (F.) after 24, 48 and 72 h. After 24-h exposure time, C. maculatus was more susceptible (LC50 = 52.47 μl/l air) and T. castaneum was more tolerant (LC50 = 279.86 μl/l air) than other species. LT50 values were indicated using highest concentration of LC50 tests for three species. In general, mortality increased as the doses of essential oil and exposure time increased. These results proposed that A. vulgaris oil might have potential as a control agent against T. castaneum, R. dominica and especially C. maculates in storages.

Fumigant toxicity of essential oils and pure compounds against Sitophilus oryzae L. (Coleoptera: Curculionidae)

In this study, Zingiber officinale (Zingiberaceae) and Piper cubeba (Piperaceae) essential oils and two pure natural terpenes, α-pinene and β-caryophyllene, were evaluated for their repellent, insecticidal and acetylcholinesterase enzyme inhibitory activities against rice weevil, Sitophilus oryzae. In the repellency assay, Zingiber officinale and Piper cubeba essential oils repelled S. oryzae adults significantly at 0.003125% while α-pinene and β-caryophyllene repelled S. oryzae adults significantly at 0.025% concentrations. Fumigation of S. oryzae adults with these essential oils and pure compounds caused lethality alone or in binary combinations. Median lethal concentrations (LC50) were 1.79, 1.07, 1.19, and 1.98 μl cm− 3 air for Z. officinale, P. cubeba essential oils, α-pinene and β-caryophyllene, respectively, against S. oryzae adults. In the case of Z. officinale+P. cubeba essential oils and α-pinene+β-caryophyllene combinations, LC50 values were 1.31, and 1.64 μl cm− 3, respectively, against S. oryzae adults. P. cubeba essential oil and α-pinene were more toxic than Z. officinale essential oil and β-caryophyllene. In binary combinations, essential oils and pure compounds did not exhibit significant synergism. Inhibition of acetylcholinesterase enzyme (AchE) activity was observed in S. oryzae adults when fumigated with sublethal concentrations of Z. officinale and P. cubeba essential oils, α-pinene and β-caryophyllene, alone or in binary combinations. These essential oils and pure compounds probably induce toxicity by inhibiting acetylcholinesterase enzyme activity.

Chemical Constituents and Toxicity of Essential Oils of Oriental Arborvitae, Platycladus orientalis (L.) Franco, against Three Stored-Product Beetles

Plant secondary metabolites play an important role in plant-insect interactions and therefore such compounds may have insecticidal or biological activity against insects. Fumigant toxicity of essential oils of leaves and fruits from oriental arborvitae (Platycladus orientalis [L.] Franco) (Cupressaceae) was investigated against adults of cowpea weevil (Callosobruchus maculatus Fab.), rice weevil (Sitophilus oryzae L.), and red flour beetle (Tribolium castaneum Herbst). Fresh leaves and fruits were subjected to hydrodistillation using a Clevenger-type apparatus and the chemical composition of the volatile oils was studied by gas chromatography-mass spectrometry (GC-MS). Twenty-six compounds (92.9%) and 23 constituents (97.8%) were identified in the leaf and the fruit oils, respectively. The major components of both leaves and fruits oils were α-pinene (35.2%, 50.7%), α-cedrol (14.6%, 6.9%) and Δ-3-carene (6.3%, 13.8%), respectively. Both oils in the same concentration were tested for their fumigant toxicity on each species. Results showed that leaf oils were more toxic than fruit oils against three species of insects. Callosobruchus maculatus was more susceptible than S. oryzae and T. castaneum. LC50 values of the leaf and the fruit oils at 24 h were estimated 6.06 and 9.24 μL L -1 air for C. maculatus, 18.22 and 21.56 μL L -1 air for S. oryzae, and 32.07 and 36.58 μL L -1 air for T. castaneum, respectively. These results suggested

Fumigant toxicity of essential oils from three Thai plants (Zingiberaceae) and their major compounds against Sitophilus zeamais, Tribolium castaneum and two parasitoids

Fumigant toxicity of essential oils from rhizomes of Alpinia conchigera, Zingiber zerumbet, Curcuma zedoaria and their major compounds; camphene, camphor, 1,8-cineole, α-humulene, isoborneol, α-pinene, β-pinene and terpinen-4-ol was investigated with adults of Sitophilus zeamais, Tribolium castaneum, Anisopteromalus calandrae and Trichogramma deion larvae. The last two insects are parasitoids commonly used to control stored-product weevils and moths. The trial was evaluated at 0, 37, 74, 148, 296, 444, 593 μL/L in air after 12, 24 and 48 h for S. zeamais, T. castaneum and A. calandrae, and 24 h for T. deion. Alpinia conchigera oils were toxic to S. zeamais, T. castaneum and T. deion, while the other two plant oils had low toxicity. Adults of S. zeamais and T. castaneum were more susceptible to A. conchigera oils than their eggs, larvae or pupae. Sitophilus zeamais adults (LC 50 85 μL/L in air) were slightly more tolerant of A. conchigera oils than T. castaneum (LC 50 73 μL/L in air) after 48 h exposure. Synthetic essential oils, a mixture of pure compounds in the same ratios of the extracted essential oils, were tested with S. zeamais and T. castaneum adults. Synthetic essential oils were more toxic than the extracted essential oils to both insects. Zingiber zerumbet oils (LC 50 26 μL/L in air) and C. zedoaria oils (LC 50 25 μL/L in air) were significantly more toxic to adults of A. calandrae than A. conchigera oils (LC 50 37 μL/L in air) whereas T. deion larvae were more sensitive to A. conchigera oils (LC 50 62 μL/L in air) than Z. zerumbet and C. zedoaria oils (LC 50 > 593 μL/L in air). Tribolium castaneum was more susceptible than S. zeamais to the eight pure compounds. Terpinen-4-ol was highly toxic to both insects.

Fumigant activity of plant essential oil from Armoracia rusticana (L.) on Plodia interpunctella (Lepidoptera: Pyralidae) and Sitophilus zeamais (Coleoptera: Curculionidae)

The fumigant toxicity of essential oil from horseradish plant, Armoracia rusticana (L.), was assessed against Plodia interpunctella (Hubner) and Sitophilus zeamais Motschulsky. A. rusticana oil was active against different life stages of P. interpunctella and adults of S. zeamais . The LC 50 value for adults was the lowest and that of pupa was the highest. The major compound found by gas chromatography-mass spectrometry was allyl isothiocyanate (97.81%). These results indicate that it may be possible to achieve toxicity levels similar to those of standard chemical fumigants through the applications of essential oils from A. rusticana .

Fumigant toxicity of essential oil from Vitex pseudo-negundo against Tribolium castaneum (Herbst) and Sitophilus oryzae (L.)

The objective of the current study was to determine the chemical constituents and fumigant toxicity of an essential oil that was isolated via hydrodistillation from dry leaves of Vitex pseudo-negundo (Hausskn.) Hand.-Mzz. The chemical composition of the essential oil was assessed via GC and GC-MS. 1, 8-Cineol (18.23%), α-Pinene (16.20%) and Sabinene (5.67%) were determined to be the major constituents of the oil. The fumigant toxicity of the essential oil was tested against 1–7 day-old adults of Tribolium castaneum (Herbst) and Sitophilus oryzae (L.) at 27 ± 1 °C and 60 ± 5% r.h. in darkness. The mortality of adults was tested at different concentrations ranging from 37.0 to 925.9 μL/L air and different exposure times (1–30 h). The results demonstrated that the mortality increased with increases in concentration and exposure time. At concentrations higher than 185.2 μL/L air, the mortality was recorded at more than 50% after 10 h, and reached 100% after 12–16 h. Data probit analysis demonstrated that S. oryzae (LC 50 = 31.96 μL/L air) was more susceptible than T. castaneum (LC 50 = 47.27 μL/L air). These results showed that the essential oil from V. pseudo-negundo could be applicable to the management of populations of stored-product insects.

Fumigant Toxicity of Essential Oils from Some Common Spices against Pulse Beetle, Callosobruchus chinensis (Coleoptera: Bruchidae)

In the present study, the essential oil from seven common spices, Anethum graveolens, Cuminum cyminum, Illicium verum, Myristica fragrans, Nigella sativa, Piper nigrum and Trachyspermum ammi was isolated and its insecticidal, oviposition, egg hatching and developmental inhibitory activities were determined against pulse beetle, Callosobruchus chinensis. Essential oils were isolated by hydrodistillation method using Clevenger apparatus. These essential oils caused death of adults and larvae of Callosobruchus chinensis when fumigated. The 24-h LC(50) values against the adults of the insect were 8.9 mul, 10.8 mul, 11.0 mul, 12.5 mul, 13.6 mul, 14.8 mul and 15.6 mul for N. sativa, A. graveolens, C. cyminum, I. verum, P. nigrum, M. fragrans and T. ammi oils respectively. On the other hand, against larval stage these values were 6.4 mul, 7.9 mul, 8.9 mul, 11.1 mul, 11.7 mul, 12.2 mul and 13.5 mul for N. sativa, A. graveolens, C. cyminum, I. verum, P. nigrum, M. fragrans and T. ammi respectively. These essential oils reduced the oviposition potential, egg hatching rate, pupal formation and emergence of adults of F(1) progeny of the insect when fumigated with sublethal concentrations. These essential oils also caused chronic toxicity as the fumigated insects caused less damage to the stored grains. The essential oil of N. sativa was found most effective against all the different stages of the Callosobruchus chinensis followed by A. graveolens, C. cyminum, I. verum, P. nigrum, M. fragrans and T. ammi oils. All the responses were found concentration-dependent. The toxic and developmental inhibitory effects may be due to suffocation and inhibition of various biosynthetic processes of the insects at different developmental stages.

Chemical constituents and fumigant toxicity of essential oil from Carum copticum against two stored product beetles

Abstract Plant secondary metabolites play an important role in plant‐insect interactions and therefore such compounds may have insecticidal or antifeedant activity against insects. Carum copticum C. B. Clarke (Apiaceae) is one of these plants that have medicinal effects on humans. The chemical composition of the essential oil from dry seeds of C. copticum was studied by gas chromatography (GC) and gas chromatography mass spectrometry (GC‐MS). Thymol (41.34%), α‐terpinolene (17.46%) and ρ‐cymene (11.76%) were found to be the major constituents of the oil. In fumigant toxicity tests with the essential oil against adults of Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) at 27 ± 1°C and 60%± 5% RH, it was observed that S. oryzae (LC50= 0.91 μL/L) were significantly susceptible than T. castaneum (LC50= 33.14 μL/L). The mortalities of the insect species reached 100% at concentrations higher than 185.2 μL/L and 12‐h exposure time. The findings indicate the strong insecticidal activity of C. copticum oil and its potential role as a fumigant for stored‐product insects.

Fumigant toxicity of essential oil from Artemisia sieberi Besser against three stored-product insects

Artemisia sieberi is a widely distributed plant in Iran. Because some species of Artemisia are insecticidal, experiments were conducted to investigate fumigant toxicity of the essential oil. Dry ground leaves were subjected to hydrodistillation using a modified Clevenger-type apparatus and the resulting oil contained camphor (54.7%), camphene (11.7%), 1,8-cineol (9.9%), β-thujone (5.6%) and α- pinene (2.5%). The mortality of 7 days old adults of Callosobruchus maculatus, Sitophilus oryzae, and Tribolium castaneum increased with concentration from 37 to 926 μL/L and with exposure time from 3 to 24 h. A concentration of 37 μL/L and an exposure time of 24 h was sufficient to obtain 100% kill of the insects. Callosobruchus maculatus was significantly more susceptible than S. oryzae and T. castaneum; a second more detailed bioassay gave estimates for the LC 50 of C. maculatus as 1.45 μL/L, S. oryzae 3.86 μL/L and T. castaneum 16.76 μL/L. These results suggested that A. sieberi oil may have potential as a control agent against C. maculatus, S. oryzae and T. castaneum.

Bazı bitki uçucu yağlarının Sitophilus oryzae L., Sitophilus granarius L. (Col.: Curculionidae) ve Acanthoscelides obtectus Say. (Col.: Bruchidae)'a karşı fumigant etkileri

Isa TELCI*** Summary Fumigant activity of some plant essential oils against Sitophilus oryzae L., Sitophilus granarius L. (Col.: Curculionidae) and Acanthoscelides obtectus Say. (Col.: Bruchidae) In this study fumigant toxicities of Salvia officinalis L. (Labiatae), Cuminum cyminum L. (Apiaceae), Anetheum graviolens L. (Apiaceae), Mentha spicata spicata L. (Labiatae), Micromeria fruticosa brachycalyx P.H. Davis (Labiatae) and Ocimum minimum L. (Labiatae) essential oils were evaluated against three important stored product insects, Acanthoscelides obtectus, Sitophilus granarius and Sitophilus oryzae, under laboratory conditions. In single dose screening test, fumigant toxicities of essential oils were tested at three different temperatures, 10, 20 and 30 °C. The results showed that M. spicata spicata and M. fruticosa brachycalyx had high fumigant toxicities to all tested insect species by 100% mortality in 24 hours. In bioassay of experiments, dosemortality studies were carried out with the promising essential oils at 20 °C. C. cyminum for A. obtectus (LC50 = 29,01 μl/l), A. graviolens for S. granarius (LC50 = 80,40 μl/l) and M. fruticosa brachycalyx for S. oryzae (LC50 = 32,25 μ l/l) appeared to be the most active essential oils.

Fumigant toxicities of essential oils and monoterpenes against Lycoriella mali adults

Toxicity of various essential oils and their volatile components against the mushroom sciarid, Lycoriella mali was determined. The most potent fumigant toxicity was found in essential oil from thyme followed by the oils of sage, eucalyptus, and clove bud. α-Pinene was the most toxic fumigant compound found in thyme essential oil ( LD 50 = 9.85 μ l / l air) followed by β-pinene ( LD 50 = 11.85 μ l / l air) and linalool ( LD 50 = 21.15 μ l / l air). The mixture of α- and β-pinene exhibited stronger fumigant toxicity than α- or β-pinene itself against the mushroom fly adults. Therefore, thyme essential oil, α- and β-pinene could be potent fumigants to control mushroom flies during mushroom cultivation.

Fumigant toxicity of essential oils from the Myrtaceae family and 1,8-cineole against 3 major stored-grain insects

Six out of 42 essential oils extracted from species of the family Myrtaceae found in Australia were shown to have potent fumigant toxicity against three major stored-grain insects: Sitophilus oryzae, Tribolium castaneum and Rhyzopertha dominica. These were the essential oils from Eucalyptus nicholii, E. codonocarpa, E. blakelyi, Callistemon sieberi, Melaleuca fulgens and M. armillaris. The LD 50 and LD 95 of the selected essential oils against S. oryzae adults were between 19.0–30.6 and 43.6–56.0 μl/l air, respectively. Also, these oils were approximately twice as toxic to T. castaneum and R. dominica at the LD 95. Fumigant effects of the essential oils rich in 1,8-cineole were considered to warrant further research into their potential for commercial use.

Biochemical mechanisms conferring cross-resistance to fumigant toxicities of essential oils in a chlorpyrifos-methyl resistant strain of Oryzaephilus surinamensis L. (Coleoptera: Silvanidae)

The fumigant toxicities of lavender and ylang-ylang essential oils were tested against a chlorpyrifos-methyl resistant strain (QVOS102) and an insecticide-susceptible reference strain (VOS48) of the saw-toothed grain beetle, Oryzaephilus surinamensis L. (Coleoptera: Silvanidae). The resistant strain showed 1.3- and 1.6-fold higher tolerance against lavender and ylang-ylang fumigation toxicity, respectively, relative to the susceptible strain. LT 50 values calculated as the time to attain 50% mortality of tested insects during fumigation were determined at two different concentrations. At 15 μl/l of air, QVOS102 had 2.9- and 1.4-fold higher LT 50 values for lavender and ylang-ylang fumigation toxicity, respectively, than VOS48. At 200 μl/l air, QVOS102 had 6.4- and 2.9-fold higher LT 50 values for lavender and ylang-ylang fumigation toxicity, respectively, than VOS48. Piperonyl butoxide, a potential inhibitor of cytochrome P450-dependent monooxygenase, increased fumigant toxicities of the two essential oils against QVOS102. The enhanced tolerance for the essential oil may have resulted from the enhancement of detoxifying enzymes associated with insecticide resistance.