Toxicity of plant essential oils and their components against Lycoriella ingenua (Diptera: Sciaridae)

Plant essential oils from 20 plant species were tested for their insecticidal activity against larvae of Lycoriella ingenua (Dufour) (Diptera: Sciaridae) by using a fumigation bioassay. Good insecticidal activity (>90%) against larvae of L. ingenua was achieved with essential oils of caraway seed Carum carvi (L.)], lemongrass [Cymbopogon citratus (D.C.) Stapf.], mandarine (Citrus reticulate Blanco), nutmeg (Myristica fragrans Houtt), cade (Juniperus oxycedrus L.), spearmint (Mentha spicata L.), cumin (Cuminum cyminum L.), and thyme red [Thymus vulgaris (L.)] oils at 30 X 10-3 mg/1 air. Among them, caraway seed, spearmint, cumin, and thyme red essential oils were highly effective against L. ingenua at 20 x 10(-3) mg/ml air. Analysis by gas chromatography-mass spectrometry led to identification of 4, 9, 8, and 17 compounds from caraway seed, spearmint, cumin, and thyme red oils, respectively. These compounds were tested individually for their insecticidal activities against larvae of L. ingenua, and compared with the toxicity of dichlorvos. Carvacrol, thymol, linalool, cuminaldehyde, p-cymen, terpinen-4-ol, and carvone was effective at 10 x 10(-3) mg/l. The insecticidal activity of dichlorvos was 60% at 10 x 10(-3) mg/ml. Effects of four selected plant essential oils on growth of oyster mushroom, Pleurotus ostreatus, also were investigated.     

Bioactivity of selected plant essential oils against the yellow fever mosquito Aedes aegypti larvae

The bioactivity of 14 essential oils from five plants has been studied using the brine shrimp lethality test and the Aedes aegypti larvicidal assay. All essential oils screened had LC50 values smaller than 200 microg/ml, showing significant lethality against brine shrimp. In addition, nine of the 14 essential oils tested showed toxicity against the fourth-instar A. aegypti larvae in 24 h (LC50<100 microg/ml). Of these, the leaf and bark essential oils of Cryptomeria japonica demonstrated high larvicidal activity, the most active being the leaf essential oil of C. japonica, with a LC50=37.6 microg/ml (LC90=71.9 microg/ml), followed by the bark essential oil of C. japonica also showing high activity against A. aegypti larvae, with a LC50=48.1 microg/ml (LC90=130.3 microg/ml). The results obtained from this study suggest that the leaf and bark essential oils of C. japonica are promising as larvicides against A. aegypti larvae and could be useful in the search for new natural larvicidal compounds.     

Insecticidal activities of leaf essential oils from Cinnamomum osmophloeum against three mosquito species

The larvicidal activities of leaf essential oils and their constituents from six chemotypes of indigenous cinnamon (Cinnamomum osmophloeum Kaneh.) trees were evaluated against three mosquito species. Results of larvicidal tests demonstrated that the leaf essential oils of cinnamaldehyde type and cinnamaldehyde/cinnamyl acetate type had an excellent inhibitory effect against Aedes albopictus larvae, and their LC(50) values in 24h were 40.8 microg/ml (LC(90)=81.7 microg/ml) and 46.5 microg/ml (LC(90)=83.3 microg/ml), respectively. Results of the 24-h mosquito larvicidal assays also showed that the effective constituents in leaf essential oils were trans-cinnamaldehyde and benzaldehyde and that the LC(50) values of these constituents against A. albopictus larvae were below 50 mug/ml. In addition, cinnamaldehyde type leaf essential oil and trans-cinnamaldehyde have also exhibited great larvicidal performance against Culex quinquefasciatus and Armigeres subalbatus larvae. Comparisons of mosquito larvicidal activity of trans-cinnamaldehyde congeners revealed that alpha-methyl cinnamaldehyde, benzaldehyde, and trans-cinnamaldehyde exhibited strong mosquito larvicidal activity.     

Fumigant toxicity of plant essential oils to Thrips palmi (Thysanoptera: Thripidae) and Orius strigicollis (Heteroptera: Anthocoridae)

The fumigant toxicity of 92 plant essential oils to adult Thrips palmi Karny (Thysanoptera: Thripidae) and Orius strigicollis Poppius (Heteroptera: Anthocoridae) was examined by using a vapor phase toxicity bioassay and compared with those of dichlorvos, emamectin benzoate, spinosad, and thiamethoxam, four commonly used insecticides. Responses varied according to oil type and insect species. As judged by 24-h LC50 values, pennyroyal oil (2.63 mg/liter air) was the most toxic fumigant and was 23.6-fold more toxic than dichlorvos (62.09 mg/liter air) against adult T. palmi. Potent fumigant toxicity (LC50, 11.03-19.21 mg/liter air) was observed in armoise, basil, cedarleaf, coriander, cypress, howood, hyssop, marjoram, myrtle, niaouli, rosemary, and sage (Dalmatia) oils. Neither emamectin benzoate, spinosad, nor thiamethoxam exhibited fumigant action. Against adult O. strigicollis, dichlorvos (LC50, 6.3 x 10(-6) mg/liter air) was the most toxic fumigant, whereas the LC50 values of the 13 essential oils ranged from 17.29 to 158.22 mg/liter air. O. strigicollis was 1.4-22.1 times less susceptible than T. palmi to the essential oils. The essential oils described merit further study as potential fumigants for the control of T. palmi in greenhouses.     

Vapor phase toxicity of plant essential oils to Cadra cautella (Lepidoptera: Pyralidae)

The toxicities of 44 plant essential oils against larvae of Cadra cautella (Walker) were examined using direct contact and vapor phase toxicity bioassays and compared with the lethal activity of chlorpyrifos-methyl, diazinon, dichlorvos, and fenthion, four widely used organophosphorus insecticides. Responses varied according to plant material used and exposure dose and time. In a filter paper contact toxicity bioassay, potent toxicity was produced from buchu leaf, niaouli, and rosemary oils at 2.4 mg/cm2 and armoise, cypress, galbanum, and mace oils at 4.7 mg/cm2. In vapor phase toxicity bioassays with larvae, cypress, galbanum, niaouli, and rosemary oils were much more effective in closed containers than in open containers, indicating that the lethal effects of these oils were largely because of action in the vapor phase. As judged by 24-h LC50 values, potent fumigant action was observed with niaouli oil (64.7 mg/liter air) and rosemary oil (64.6 mg liter/air). Cypress and galbanum oils exhibited weak fumigant activity. These essential oils were less active than dichlorvos (0.86 mg/liter air). Little or no fumigant action was observed with chlorpyrifos-methyl, diazinon, and fenthion. Essential oils described herein, particularly niaouli and rosemary oils, merit further study as potential larvicides for the control of C. cautella.     

Effects of essential oils on Aedes aegypti larvae: alternatives to environmentally safe insecticides

The essential oils from leaves of Hyptis fruticosa (Lamiaceae) Salzm., H. pectinata (Lamiaceae) Poit., and Lippia gracilis (Verbenaceae) HBK were investigated for their larvicidal activity against Aedes aegypti and analyzed by GC/MS. Fifty-nine compounds, representing 91.28-98.39% of the essential oils, have been identified. A standard solution was used to make 20 mL solutions ranging from 30 to 2000 ppm. Twenty larvae between third and fourth stages were added to the essential oil solution. A mortality count was conducted 24 h after treatment. Essential oils LC50 and their confidence limits at 95% probability were calculated by the methods of Reed-Muench and Pizzi, respectively. The essential oil of Lippia gracilis showed potent insecticidal effect against Aedes aegypti larvae, the vector of dengue fever. Carvacrol and caryophyllene oxide were the main responsible for the activity of L. gracilis and H. pectinata. Minor compounds are probably acting synergistically to achieve H. fruticosa activity.     

Castor and camphor essential oils alter hemocyte populations and induce biochemical changes in larvae of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae)

Two plant essential oils; camphor and castor were tested for insecticidal and antifeedant activity against the 4th instar larvae of Spodoptera littoralis, a serious pest on cotton in Egypt. Also the impact of LC₁₀ of both oils on some physiological parameters in larvae was studied by using leaf dipping technique. Analysis of both oils using GC–MS revealed several insecticidal and antifeedant compounds. Our results showed higher insecticidal activity and antifeedant index of camphor oil against S. littoralis. The LC₅₀ and the antifeedant indices were 163.1, 246.8?mg/ml and 12.69, 6.62% for camphor and castor bean oil, respectively. The total hemocyte count (THC) and differential hemocyte count (DHC) were reduced significantly after 48?h of treatment compared to controls. Both oils reduced all types of hemocytes except plasmatocytes which were reduced only by castor oil. Camphor oil decreased total proteins and carbohydrates while castor oil targeted only carbohydrate content. Both oils didn't affect the amount of total lipids. Lipase, α-amylase and glucose-6-phosphate dehydrogenase (G6PD) enzyme activities were increased significantly in larvae treated with camphor oil than other treatments. These results clearly indicate that castor and camphor oils can affect the nutritional status in S. littoralis larvae, thereby changing the internal metabolic processes in the larvae which make them as potential control agents in IPM programs against S. littoralis.     

Chemical composition and fumigant toxicity of some essential oils against Ephestia kuehniella

The chemical constituents of some essential oils extracted from aromatic plants (savory, Satureja thymbra L.; Turkish oregano, Origanum onites L.; myrtle, Myrtus communis L.; marjoram, Origanum majorana L.; laurel, Laurus nobilis L.; lemon, Citrus limon L.; sticky goosefoot, Chenopodium botrys L.; and tansy, Tanecetum armenum [DC.] Suchultz Bip.) were analyzed by gas chromatography-mass spectrometry. Fumigant toxicity of volatile compounds was tested against Mediterranean flour moth, Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae), eggs and adults. Percentage of mortality and longevity of E. kuehniella adults were estimated after essential oil treatments. LC50 and LC99 values were determined for each exposure time for each essential oil. Marjoram and lemon oils were the most effective of all the essential oils tested. The major components were linalool, 1.8-cineole, citral, 2-(4a.8-dimethyl-1.2.3.4.4a.5.6.7-octahydro-naphthalen-2-yl)-prop-2-en-l-ol, and p-cymene for marjoram, laurel, lemon, goosefoot, and tansy, respectively. The LC50 and LC99 values were estimated as 3.27 and 5.13 microl liter(-1) air for marjoram and 4.05 and 5.57 microl liter(-1) air for lemon essential oils at the longest exposure time. Decreasing longevity effect of marjoram and lemon was more prominent compared with other essential oils. We suggest that essential oils obtained from certain aromatic plants have potential as fumigants for stored product pests.     

Fumigant activity of essential oils and components of Illicium verum and Schizonepeta tenuifolia against Botrytis cinerea and Colletotrichum gloeosporioides

To develop a natural fungicide against Botrytis cinerea and Colletotrichum gloeosporioides, a total of 25 essential oils were tested for their fumigant activity against post-harvest pathogens. The vaporous phases of oils were treated to each fungus on potato dextrose agar medium in half-plate separated Petri plates at 10 microg per plate. The essential oil of Illicium verum strongly inhibited the mycelial growth of both B. cinerea and C. gloeosporioides by over 90%. On the other hand, the essential oil of Schizonepeta tenuifolia showed inhibitory activity against mycelial growth of only B. cinerea by over 90%. Gas chromatography-mass spectrometry and bioassay indicated trans-anethole in I. verum and menthone in S. tenuifolia as a major antifungal constituent. The essential oils of I. verum and S. tenuifolia and their major constituents could be used to manage post-harvest diseases caused by B. cinerea and C. gloeosporioides.     

Toxicity of plant essential oils to Trialeurodes vaporariorum (Homoptera: Aleyrodidae)

A total of 53 plant essential oils were tested for their insecticidal activities against eggs, nymphs, and adults of Trialeurodes vaporariorum Westwood, using an impregnated filter paper bioassays without allowing direct contact. Responses varied according to oil type and dose, and developmental stage of the insect. Bay, caraway seed, clove leaf, lemon eucalyptus, lime dis 5 F, pennyroyal, peppermint, rosewood, spearmint, and tea tree oils were highly effective against T. vaporariorum adults, nymphs, and eggs at 0.0023, 0.0093, and 0.0047 microl/ml air, respectively. These results indicate that the mode of delivery of these essential oils was largely a result of action in the vapor phase. Significant correlations among adulticidal, nymphicidal, and ovicidal activities of the test oils were observed. The essential oils described herein merit further study as potential fumigants for T. vaporariorum control.     

Potential use of essential oils from Cameroon applied as fumigant or contact insecticides against Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

Essential oils from seven plants species currently found in Cameroon were extracted by steam distillation and tested for their insecticidal activities against Sitophilus zeamats Motsch. Responses varied with the test applied and the plant species. For the contact toxicity, the acetone was used in order to dilute the pure essential oil. Formulations of 1% of essential oils of Xylopia aethiopica and Ocimum gratissimum were the most toxic and led to 96 and 98% of mortality respectively after 24 h. There was no death in control (0% of mortality). Fumigation test were done by applying 300 microl of pure essential oils in the bottom of closed 800 ml glass containers. In that case, the essential oil of Hyptis spicigera was the most toxic (fumigant) after 48 hours of fumigation followed by Annona seregalensis and Xylopia aethiopica 96 and 95% of mortality respectively. Some of the essential oils of plant species tested are promising for pest control in farmer granaries. However, further investigations are to be done on formulation and side effects.     

Repellent and insecticidal activities of essential oils from Artemisia princeps and Cinnamomum camphora and their effect on seed germination of wheat and broad bean

Repellent and insecticidal activities of essential oils extracted from leaves of Artemisia princeps Pamp and seeds of Cinnamomum camphora (L.) Presl. against storage pests Sitophillus oryzae L. and Bruchus rugimanus Bohem were investigated. Results showed that the two individual oils displayed good, but their mixture (1:1) exhibited much better repellent activities at concentrations from 250 to 1000 microg g(-1) and insecticidal actions at concentrations 1000 microg g(-1) against the test beetles S. oryzae and B. rugimanus. Oils from A. princeps and C. camphora applied individually were significantly toxic to seed germination of wheat at 500 microg ml(-1). However, no toxic effects were found when the two oils were mixed (1:1 w/w) at the same concentration. These observations indicated that the mixture of the two plant-derived oils had a synergic effect and could be used in the control of storage pests.     

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.     

Chemical polymorphism and antifungal activity of essential oils from leaves of different provenances of indigenous cinnamon (Cinnamomum osmophloeum)

The essential oils isolated from nine geographical provenances of indigenous cinnamon (Cinnamomum osmophloeum Kaneh.) leaves were examined by GC-MS and their chemical constituents were compared. According to GC-MS and cluster analyses the leaf essential oils of the nine provenances and their relative contents were classified into six chemotypes-cinnamaldehyde type, cinnamaldehyde/cinnamyl acetate type, cinnamyl acetate type, linalool type, camphor type and mixed type. In addition, the antifungal activities of leaf essential oils and their constituents from six chemotypes of indigenous cinnamon were investigated in this study. Results from the antifungal tests demonstrated that the leaf essential oils of cinnamaldehyde type and cinnamaldehyde/cinnamyl acetate type had an excellent inhibitory effect against white-rot fungi, Trametes versicolor and Lenzites betulina and brown-rot fungus Laetiporus sulphureus. The antifungal indices of leaf essential oils from these two chemotypes at the level of 200 micro/ml against T. versicolor, L. betulina and L. sulphureus were all 100%. Among them, the IC(50) (50% of inhibitory concentrations) value of the essential oil of cinnamaldehyde type leaf against L. sulphureus was 52-59microg/ml. Cinnamaldehyde possessed the strongest antifungal activities in comparison with other constituents of the essential oils from cinnamaldehyde type leaf, at the level of 100microg/ml its antifungal indices against T. versicolor, L. betulina and L. sulphureus were 100%. The IC50 values of cinnamaldehyde against T. versicolor, L. betulina and L. sulphureus were 73, 74 and 73microg/ml, respectively.     

Insecticidal and synergistic effects of Majorana hortensis essential oil and some of its major constituents

The essential oil from leaves of Majorana hortensis Moench (Lamiaceae) was isolated by hydrodistillation with a yield of 1.6% (wt/wt). The insecticidal activity of the oil was evaluated against fourth instars of Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae) and adults of Aphis fabae L. (Hemiptera: Aphididae). The oil showed a remarkable toxic effect against S. littoralis in a topical application assay (LD₅₀ = 2.48 μg per larva) and in a residual film assay (LC₅₀ = 3.14 g/l). The oil of M. hortensis also exhibited a pronounced toxic effect against A. fabae adults with LC₅₀ values of 1.86 and 2.27 g/l in rapid dipping and residual film assays, respectively. Gas chromatography-mass spectrometry analyses of M. hortensis essential oils revealed the presence of 31 compounds and the main components were terpinen-4-ol (30.0%), γ-terpinene (11.3%), and trans -sabinene hydrate (10.8%). Repeated column chromatography of M. hortensis oil on silica gel led to the isolation of two major constituents, which were characterized based on ¹H-nuclear magnetic resonance and mass spectrometric data, as terpinen-4-ol and γ-terpinene. These two components were examined for their insecticidal and synergistic activities towards S. littoralis and A. fabae . Terpinen-4-ol and γ-terpinene exhibited a significant insecticidal activity against both insects, but γ-terpinene was more toxic than terpinen-4-ol. When tested in a binary mixture with the synthetic insecticides profenofos and methomyl, it was found that both compounds enhanced the insecticidal activity of these insecticides by two- to threefold. These results show that terpinen-4-ol and γ-terpinene have a synergistic effect on the insecticidal activities of synthetic insecticides profenofos and methomyl.     

Insecticidal, repellent and oviposition-deterrent activity of selected essential oils against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus

Essential oils extracted from 10 medicinal plants were evaluated for larvicidal, adulticidal, ovicidal, oviposition-deterrent and repellent activities towards three mosquito species; Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. The essential oils of Juniperus macropoda and Pimpinella anisum were highly effective as both larvicidal and ovicidal. The essential oil of P. anisum showed toxicity against 4th instar larvae of A. stephensi and A. aegypti with equivalent LD95 values of 115.7 microg/ml, whereas it was 149.7 microg/ml against C. quinquefasciatus larvae. Essential oils of Zingiber officinale and Rosmarinus officinalis were found to be ovicidal and repellent, respectively towards the three mosquito species. The essential oil of Cinnamomum zeylanicum resulted into highest repellent (RD95) values of 49.6, 53.9 and 44.2 mg/mat against A. stephensi, A. aegypti and C. quinquefasciatus, respectively apart from oviposition-deterrent potential.     

Fumigant Toxicity of Plant Essential Oils to Plutella xylostella (Lepidoptera: Yponomeutidae) and Cotesia glomerata (Hymenoptera: Braconidae)

The fumigant toxicity of 66 plant essential oils to Plutella xylostella (L.) larvae and Cotesia glomerata (L.) adults was examined using a vapor-phase toxicity bioassay and compared with that of dichlorvos. Responses varied according to oil and insect species used. Based on 24 h LD₅₀ values, pennyroyal oil [10.77 mg/filter paper (4.25 cm diameter)] was the most toxic fumigant, followed by rosemary and sage (Dalmatin) oils (15.15 mg/paper). Potent fumigant toxicity was also produced from armoise, buchu leaf, cedarleaf, coriander, eucalyptus, howood, lavender, myrtle, niaouli, peppermint, and rosewood oils (LD₅₀, 21.29–27.31 mg/paper). All essential oils were less effective than dichlorvos (LD₅₀, 0.52 mg/paper). Against adult C. glomerata, dichlorvos (LD₅₀, 0.03 mg/paper) was the most toxic fumigant, whereas the LD₅₀ values of the 14 essential oils ranged from 1.59 to 8.51 mg/paper. Based on selective toxicity ratio (STR, P. xylostella LD₅₀/C. glomerata LD₅₀), the 14 essential oils (STR, 2.5–14.5) are more selective than dichlorvos (STR, 17.3). The essential oils tested merit further study as potential fumigants for the control of P. xylostella in greenhouses because of their selective toxicity to adult C. glomerata and their much greater activity as a fumigant.     

Toxicity of plant essential oils to Tetranychus urticae (Acari: Tetranychidae) and Phytoseiulus persimilis (Acari: Phytoseiidae)

Fifty-three plant essential oils were tested for their toxicity against eggs and adults of Tetranychus urticae Koch as well as adults of Phytoseiulus persimilis Athias-Henriot, by using a filter paper diffusion bioassay without allowing direct contact. Responses varied according to oil type and dose, and mite species. In a plastic container (4.5 by 9.5 cm) bioassay at 14 x 10(-3) microl/ml air, caraway seed, citronella java, lemon eucalyptus, pennyroyal, and peppermint oils gave > 90% mortality against adult T. urticae, whereas 82 and 81% mortality was observed with sage and spearmint oils, respectively. With the exception of sage oil, the other six essential oils were highly effective against T. urticae eggs at 9.3 x 10(-3) microl/ml air. Against adult P. persimilis, these six test oils caused > 90% mortality at 7.1 x 10(-3) microl/ml air. Particularly peppermint oil at 4.7 x 10(-3) microl/ml air was highly toxic. In an acrylic cage (30 by 30 by 40 cm ) test, lemon eucalyptus, pennyroyal, peppermint, and spearmint oils were highly effective against adult T. urticae at 1.4 x 10(-3) microl/ml air. These results indicate that the mode of delivery of these essential oils was largely a result of action in the vapor phase via the respiratory system. The essential oils described herein merit further study as potential fumigants for T. urticae control.     

A study of the larvicidal activity of Origanum (Labiatae) species from southwest Turkey.

The insecticidal activity of essential oils isolated from two species of Origanum (Origanum onites L. and Origanum minutiflorum (O. Schwarz and P.H. Davis) (Labiate)) was investigated against 3rd and 4th instar larvae of the mosquito, Culex pipiens L. (Diptera: Culicidae). The LC50 and LC90 values were 24.8 and 61.3 ppm, and 73.8 and 118.9 ppm, respectively. This activity was attributed to the carvacrol, the major constituent of these oils.     

Insecticidal activity of selected monoterpenoids and rosemary oil to Agriotes obscurus (Coleoptera: Elateridae)

Acute toxicities of three naturally occurring monoterpenoid essential oil constituents and the essential oil of rosemary were tested against late instars of Agriotes obscurus (L.) (Coleoptera: Elateridae). Both contact and volatile toxicities of thymol, citronellal, eugenol, and rosemary oil were determined. Also, phytotoxicity of these compounds was evaluated on corn germination and seedling development. Thymol had the greatest contact toxicity (LD50 = 196.0 microg/larva), whereas citronellal and eugenol were less toxic (LD50 = 404.9 and 516.5 microg/larva, respectively). Rosemary oil did not show any significant contact toxicity, even at 1,600 microg/larva. In terms of volatile toxicity, citronellal was the most toxic to wireworm larvae (LC50 = 6.3 microg/cm3) followed by rosemary oil (LC50 = 15.9 microg/cm3), thymol (LC50 = 17.1 microg/cm3), and eugenol (LC50 = 20.9 microg/cm3). Thymol, eugenol, and citronellal significantly inhibited corn seed germination and development, whereas rosemary oil had only minimal phytotoxic effects.