Toxic and deterrent effects of two volatile oils against cowpea weevil,Callosobruchus chinensis (Coleoptera: Bruchidae)

The fumigant effect of Mentha piperita and Ocimum basilicum oils and their mixture against adults and eggs of Callosobruchus chinensis (L.) was evaluated. Bioassay experiments showed that Ocimum basilicum oil was significantly effective against adult and egg stage which was the least effective. However, in the fumigant toxicity experiments against adult stage, Ocimum basilicum oil at a dose of 1.0 μl/38.5 ml air caused 100% mortality (LC₅₀ = 1.88), the mixture of both oils at a dose of 6.0 μl/38.5 ml air caused 100% mortality (LC₅₀ = 10.3) and Mentha piperita oil at a dose of 80.0 μl/38.5 ml air caused 80.0% mortality (LC₅₀ = 41.224) during a one day exposure period. Regarding the oviposition deterrent activity, Ocimum basilicum oil achieved 100% oviposition deterrent (at a dose of 0.5 μl/38.5 ml air) followed by the mixture of Mentha piperita and Ocimum basilicum oils, which achieved 71.22% oviposition deterrent (at a dose of 1.0 μl/38.5 ml air) and Mentha piperita oil, which achieved 39.6% oviposition deterrent (at a dose of 5.0 μl/38.5 ml air). The essential oils and their mixtures studied here determined a significant decrease in the number of eggs hatched and in the emergence of adults. The eggs failed to hatch on using Ocimum basilicum oil at a dose of 0.6 μl/38.5 ml air. However, the number of eggs hatched decreased to 7.4 on using a mixture of oils at a dose of 2.0 μl/38.5 ml air and 14.0 with Mentha piperita oil at a dose of 80.0 μl/38.5 ml air compared with 25.0 eggs hatched in the control experiments. On the other hand, the percentage reduction in emerging adults were 100% for Ocimum basilicum oil, 90.9% for a mixture of the two oils and 72.7% for Mentha piperita oil. Results showed that Ocimum basilicum oil and Ocimum basilicum oils plus Mentha piperita oils in blend are potential alternatives to synthetic fumigants in the treatment of durable agricultural products. Successful adoption of plant oils in the protection of food commodities promises an eco-friendly option compatible with international biosafety regulations.     

Control of stored grain pest,Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), using the essential oils isolated from Zingiber officinale (L.) and Mentha pulegium (L.) in laboratory condition

Fumigant activity of essential oil vapours distilled from Zingiber officinale (L.) and Mentha pulegium (L.) was tested against eggs, larvae and adults of Callosobruchus maculatus (F.). Fumigant toxicity was assessed at 27?±?1?°C and 60?±?5% RH, in dark condition. The influence of different concentrations of the essential oil vapours on egg hatchability, larval and adult mortality was significant. Data probit analysis showed that lethal concentration of the essential oil to kill 50% of the population (LC₅₀) for egg, larvae and adult was found to be 1.151, 2.336 and 2.183?μl/l air of Z. officinale, followed by 0.072, 0.113 and 0.093?μl/l air essential oil of M. pulegium, respectively. Between these essential oils, Z. officinale is almost more toxic than M. pulegium on all growth stages of C. maculatus. The present study suggests that essential oils from these medicinal plants may be potential grain protectants as botanical alternative fumigants and could be used in the management of various life stages of C. maculatus.     

Efficacy of artificial seeds in the delivery of bioactive compounds to the seed dwelling larvae of Callosobruchus maculatus (Coleoptera: Bruchidae)

Artificial seeds offer an important method to assay the bioactivity of natural and synthetic compounds against insect larvae that develop within the cotyledons of seeds. Here, the efficacy of artificial seeds as a mechanism to deliver bioactive compounds to larvae of the bruchid beetle, Callosobruchus maculatus, was compared to that of black-eyed beans that had been imbibed with the same bioactive compounds: malachite green or the methanolic extract of neem (Azadirachta indica). Females laid an equivalent number of eggs on control artificial seeds in comparison with black-eyed beans, although egg-to-adult survival on artificial seeds was reduced. Manipulation of the hardness of artificial seeds influenced female oviposition decisions, with more eggs laid on the harder seeds, although seed hardness had no effect on egg-to-adult survival. Incorporation of neem extract or malachite green into the artificial seeds resulted in 100 % larval mortality, while larval mortality on seeds imbibed with neem extract or malachite green was between 50 and 70 %. This suggests incorporation of toxins into artificial seeds, produces a more sensitive assay of compound toxicity in comparison with the method of imbibing seeds and offers a useful method to study of seed–arthropod interactions.     

Nano essential oils against the red palm weevil,Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae)

The red palm weevil, Rhynchophorus ferrugineus, is the biggest pest of various palm species. The aim of this study was to evaluate the impact of the essential oils of purslane, mustard and castor (bulk and nano) on R. ferrugineus and to evaluate the oviposition deterrent effect to prevent new infestations. Prepared concentrations of essential oils (bulk and nano) were tested for their impact on R. ferrugineus larvae, pupae and adults. The most effective oil was purslane oil (bulk and nano), followed by mustard and the least effective was castor. The percent mortality of larvae was 75.2, 45.3 and 17.9% (bulk phase) and 92.5, 84.4 and 65.5% (nano phase) in purslane, mustard and castor, respectively, when treated with the high concentration. The percent mortality of adults was 67.2, 40.0 and 15.6% (bulk phase) and 83.5, 72.9 and 60.0% (nano phase) in purslane, mustard and castor, respectively, when treated with the high concentration. The number of eggs laid decreased with increasing concentration of the tested oils. Purslane essential oil showed good impact on R. ferrugineus larvae and adults followed by mustard and castor oils as bulk and as nano.     

Biological activity of tree marigold, Tithonia diversifolia, on cowpea seed bruchid, Callosobruchus maculatus (Coleoptera: Bruchidae)

The powder and ethanol extract of Tithonia diversifolia leaves were tested for their efficacy at five different concentrations (0.0%, 0.5%, 1.0%, 1.5% and 2.0%) on bruchid mortality, oviposition and adult emergence of cowpea seed beetle Callosobruchus maculatus at ambient tropical storage conditions of temperature and relative humidity. Results showed that the leaf extract had a higher bioactivity on oviposition, adult emergence and mortality of C. maculatus. The mean number of eggs laid on seeds treated with extract was reduced from 20.7 in the solvent-treated to 4.7 at 2%Tithonia extract concentration while adult emergence reduced from a mean of 92.2 in the solvent-treated seeds to 72.2 at 2.0% extract treatment. Mortality was 100% at higher concentrations of 3%, 4% and 5% within 24 h of extract application but at lower concentrations mortality was 73.3% and 93.3% at 1% and 2%, respectively after 24 h. Fourty-eight hours after application, 100% mortality of adult C. maculatus was obtained at all concentrations. The mean number of eggs laid was reduced from 41.3 in the untreated to 17.3 at 2.0% powder concentration while adult emergence dropped from 98.5% in the control to 74.2% at the highest powder concentration. The powder was effective at higher concentrations and longer exposure time. At 3%, 4% and 5%, 63–75% mortalities occurred within 24 h of application while at 48 h, mortality was 76–98% at 3–5% powder application rates. The results of this study revealed T. diversifolia as a potential candidate for bioinsecticide preparations because of antiovipositional, ovicidal and knockdown properties of its products, which have some volatile components.     

香茅精油对桔小实蝇产卵驱避作用及其化学成份分析

研究了香茅Cymbopogon nardus精油对桔小实蝇Bactrocera dorsalis (Hendel)的产卵驱避作用及其化学成分。结果表明,香茅精油对桔小实蝇产卵具有一定的驱避作用,不同浓度香茅精油处理芒果上的产卵量均显著低于对照,且随着香茅精油浓度的提高其产卵量逐渐减少,当浓度为10000μg/mL时,产卵驱避率为70.06%。采用气相色谱—质谱联用(GC-MS)技术分析了香茅精油的化学成份,结果发现该精油挥发物中含量较高的是3-蒈烯,香茅醛,香叶醇,香茅醇,柠檬烯。     

Response of cowpea bruchid,Callosobruchus maculatus (Fab.) (Coleoptera: Chrysomelidae) to cheese wood,Alstonia boonei De Wild stem bark oil extracted with different solvents

Cheese wood, Alstonia boonei De Wild stem bark was extracted with five different solvents namely: methanol, ethanol, acetone, petroleum ether and n-hexane. The extracts were tested for insecticidal activity on cowpea bruchid, Callosobruchus maculatus (Fab.). Adult mortality and adult emergence of the insects were investigated. Oviposition deterrences using dual-choice and multiple-choice tests were also investigated as well as percentage damage and weight loss at temperature of 28?±?2?°C and 75?±?5% relative humidity. Results showed that at the rate of 2% extract per 20?g of cowpea seeds, methanol, petroleum ether and n-hexane extracts caused 100% mortality of adult cowpea bruchid after four?days of post treatment. When the bruchid had choice of oviposition substrate, they laid significantly (p?<?0.05) fewer eggs on cowpea seeds treated with extracts compared to untreated seeds. There was no adult emergence in seeds treated with methanol, ethanol, petroleum ether and n-hexane extracts and 100% reduction in F₁ progeny was recorded compared with untreated that had 81.86% adults emergence and 0% reduction in F₁ progeny. The results obtained from this study revealed that methanol, ethanol, acetone, petroleum ether and n-hexane extracts of A. boonei stem bark were effective in controlling C. maculatus and could serve as an alternative to synthetic insecticides for the protection of stored cowpeas against bruchids.     

Methyl salicylate,thymol and carvacrol as oviposition deterrents for Frankliniella occidentalis (Pergande) on plum blossoms

A bioassay was developed to determine whether treatment with essential oils thymol, methyl salicylate and carvacrol can reduce the oviposition rate of western flower thrips (wft), Frankliniella occidentalis, on plum blossoms. Individual field-collected wft females were confined on single blossoms treated with three concentrations of essential oils applied in different suspensions: an aqueous 0.05 % Triton X-100 plus ethanol solution [ethanol/water/Triton (EWT)], an EWT plus Citrex^® medium mineral oil and an aqueous 0.05 % Triton X-100 solution (water/Triton) plus Citrex^®. The number of eggs laid per female over 24 h was compared to oviposition on untreated blossoms and those treated with control suspensions. A 10 % suspension of thymol significantly reduced oviposition rate by 85 % compared with blossoms treated with control suspension and untreated. Methyl salicylate concentrations of 10 and 1 % significantly reduced oviposition rate by 84 and 88 %, respectively, compared with the control suspension and, 89 and 85 %, respectively compared with the untreated. Carvacrol concentrations of 5, 1 and 0.1 % significantly reduced oviposition rate compared with untreated blossoms (84, 53 and 57 %), whilst the 5 % was also significantly different to the control suspension (69 % reduction). Suspension type had no significant effect on mean oviposition rate. We have shown that these essential oils are effective in reducing wft egg-laying when applied to fragrant flowers and have potential for inclusion in pest management strategies for this pest on plums. Further research is required to develop stable suspensions that provide an even deposit, more sustained release and that can reduce the phytotoxicity observed with the higher concentrations.     

Comparative seed resistance in eighty cowpea accessions to the seed bruchid,Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae)

Eighty cowpea accessions comprising both improved and local were assessed for their resistance to Callosobruchus maculatus (F.) attack under laboratory conditions (29 ± 3?°C and 65 ± 5% R.H.). Sixty-nine accessions were derived from the International Institute for Tropical Agriculture breeding programmes, four were local cultivars, while seven were improved cultivars from national research institutes. Results showed that there were significant differences among the accessions in terms of number of initial bruchid eggs laid on them, adult emergence, number of seeds damaged and bruchid-induced seed weight loss at three months after artificial infestation with C. maculatus. On IT04K-334-2, IT04K-343-1, IT06K-141, IT99K-216-48-1, IT99K-494-6 and IT99K-529-2, fewer initial eggs were laid and no adult emergence, seed damage or weight loss and were considered highly resistant to C. maculatus. On the other hand, IT03K-337, IT04K-217-51, IT04K-332-1, IT04K-339-1, IT06K-188-49, IT81D-1137, IT845-2231-15, IT93K-452-1, IT04K-154-1, IT96K-610, IT97K-1069-6, IT97K-390-2, Ife Bpc, IT99K-573-2-1, Ife Modupe, IT845-2246, Drum, Ife Brown and Oloyin were the most susceptible with the highest damage indices values (p?<?0.05). The range of each of the resistance indices measured in the susceptible varieties was: number of initial eggs laid (61–100), adult emergence (40.0–62.10%), number of seeds damaged (53.0–85.5) and seed weight loss (58.0–66.25%).     

Acute toxicity of kaolin and essential oils from Mentha pulegium and Zingiber officinale against different stages of Callosobruchus maculatus under laboratory conditions

Naturally derived compounds such as essential oils and natural mineral are relatively cheap, non-toxic to food grains and environmentally friendly and would be suitable alternatives for currently used chemical insecticides if they have high insecticidal effectiveness. In the present study, acute toxicity of kaolin and essential oils from Mentha pulegium and Zingiber officinale were assessed on different stages of Callosobruchus maculatus at 28?±?2?°C, 65?±?5% R. H and dark condition. The calculated LC₅₀ values on the egg, larvae and adult stages of C. maculatus were 1.15, 2.33 and 2.18?μl/ml air for Z. officinale and 0.07, 0.11 and 0.09?μl/ml air for M. pulegium, respectively. The result showed that M. pulegium was more effective essential oil against different stages of C. maculatus compared with the Z. officinale, and also the egg and adult stages of C. maculatus were more susceptible against essential oils compared with larval stage. The LC₅₀ values of kaolin were 0.71 and 0.18?mg/cm² on egg and adult of C. maculatus, respectively. The combination of tested essential oils with kaolin increased mortality of C. maculatus adults compared with their application alone. It was found that tested essential oils and kaolin had high potential in controlling different stages of C. maculatus.     

Repellency and toxicity of extract from Francoeria crispa (Forsk.) to Eutetranychus orientalis (Klein) (Acari: Tetranychidae)

Laboratory bioassays were conducted to characterise the activity of the extract Francoeria crispa (Forsk.) (Family: Compositae) against the citrus brown mite, Eutetranychus orientalis (Klein). Ethyl acetate was tested for preparing the crude extract of F. crispa. The extract was tested for its toxicity against eggs and adult females of the pest E. orientalis. Ethyl acetate extract of F. crispa affected the behaviour, toxicity and fecundity of females under laboratory conditions. The extract had similar toxic effects on egg stage and adult females of E. orientalis (LC₅₀ = 0.00050 g/ml), respectively. Leaf discs treated with increasing concentrations of ethyl acetate extract of F. crispa showed a high percentage of repellency (97.45%), respectively. Treated females with LC₅₀ concentration of ethyl acetate extract showed a higher remarkable percentage of mortality as well as a reduction in the total number of eggs laid during 7 days. Ten isolated fractions of ethyl acetate crude extract from F. crispa were detected. The results clearly indicate that the isolate number (10) was the most toxic isolate on eggs and females of E. orientalis (LC₅₀ = 0.00014 and 0.000125 g/ml), respectively.     

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.     

Effectiveness of Metarhizium anisopliae formulations against dengue vectors under laboratory and field conditions

The oviposition behaviour of Aedes aegypti and the effectiveness of Metarhizium anisopliae conidia formulated in water or oil-in-water against A. aegypti adults and eggs were tested in multi-choice and no-choice tests in oviposition devices under laboratory conditions. Both females and males rested in the devices, regardless of the formulation, and were not repelled by the presence of conidia (up to 10⁶?conidia/cm²) without oil or formulated with oil on treated filter paper arranged in the device. However, at higher oil concentrations (≥0.1?μl/cm²), regardless of the presence of conidia, the number of eggs laid by gravid females on the filter paper dropped. The susceptibility of adults, especially of males, to fungal infection increased up to a 15-day incubation. An elevated number of larvae (≥41%) eclosed from eggs laid on the moistened filter paper in the device even without submersion of eggs in water, and these larvae subsequently died. In the laboratory, 1?μl/cm² oil combined with 10⁶?conidia/cm² clearly reduced eclosion to 1.8% after submersion of eggs in water compared to ≥13% eclosion in the control. In field tests in Goiânia, Brazil, eclosion of aedine larvae from eggs laid on filter paper previously treated with oil-in-water formulated conidia dropped to between 0% and 36% compared to 22–50% in the control. Promising results of laboratory and field tests with M. anisopliae formulated in water or oil-in-water and tested in a device emphasised the effectiveness of a fungus-based formulation for aedine mosquitoes in peridomestic areas.     

Mechanism and effectiveness of safflower oil against female Queensland fruit fly Bactrocera tryoni

Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), infests many horticultural fruit crops in the eastern part of Australia. Farmers usually apply synthetic insecticides to control this pest. Little is known on the use of plant products especially vegetable oils for fruit fly control although they are considered to be safer than synthetic insecticides. In this study, safflower oil was investigated for its mechanism and effectiveness against female B. tryoni. In a laboratory test, safflower oil treatments (2.5 and 5.0 ml l^?1) reduced the number of fly punctures on treated artificial fruits, no matter whether pre‐punctures were present or absent. Safflower oil treatments also reduced the number of fly landings and eggs laid, but only when the treated artificial fruits were without pre‐punctures. These results confirmed that safflower oil is active against female B. tryoni mainly by preventing this fruit fly from making oviposition punctures, not by discouraging them from depositing eggs or by repelling them. The slippery nature of safflower oil is considered to be responsible for a reduction in the susceptibility of artificial fruit to fruit fly punctures. Further investigation using fruit‐bearing tomato plants (a no‐choice test) in a glasshouse situation revealed that safflower oil application at concentrations of 10 and 15 ml l^?1 reduced the number of oviposition punctures but failed to reduce the number of eggs laid. To increase efficacy of safflower oil under field conditions, multiple tools may be needed to reduce fruit fly populations and oviposition behaviour, such as the addition of trap‐crops, provision of artificial oviposition sites, or mixing the insecticides with the oil.     

Protection of cowpea,Vigna unguiculata L. (Walp.) with Newbouldia laevis (Seem.) extracts against infestation by Callosobruchus maculatus (Fabricius)

Evaluation of protectant ability of Newbouldia laevis (Seem.) extracts against infestation by Callosobruchus maculatus in cowpea, Vigna unguiculata L. (Walp.) was carried out in the laboratory at ambient temperature of 28?±?2?°C and 70?±?5% relative humidity. Extracts from wood ash, leaf, stem and root bark were tested at different concentrations of 0, 1, 2, 3, 4 and 5%. One hundred per cent mortality of adult beetles was achieved at all concentrations within 72?h of treatment with extracts except in wood ash at 1% concentration, but they were significantly different (p?<?0.05) from the controls. All the extracts were still able to cause high beetle mortality after one, two and three months of cowpea storage at high concentrations (4 and 5%) except wood ash, although there was a slight decrease in mortality during the period of storage. All the extracts significantly (p?<?0.05) reduced oviposition and adult emergence of C. maculatus when compared with the controls although the reduction was higher at 5% concentration than others. Adult beetle emergence was completely prevented at higher concentrations (4 and 5%) except in wood ash. Both oviposition and adult emergence increased during the months of storage probably because of the slight reduction in the effectiveness of the extracts. The root bark extract was much more effective in reducing oviposition and adult emergence than others throughout the period of storage. The plant extracts of N. laevis was able to protect the cowpea seeds from damage and prevent weight loss. Cowpea seed damage and weight loss was significantly more (p?<?0.05) in the controls than other for the three-month duration probably because of the more adult emergence. The extracts from N. laevis did not adversely affect the germination of the protected seeds and seed germination ranged from 86.7 to 100%. It has been shown in this study that the extracts of N. laevis were effective against C. maculatus in cowpea although the root bark extract seemed to be the most effective while the wood ash extract was least effective. Their effectiveness, however, slightly decreased during the period of storage. N. laevis could be incorporated into pest management of stored cowpeas since the products are ecologically safe.     

Efficacy of Elettaria cardamomum L. (Zingiberaceae) essential oil on the two spotted spider mite,Tetranychus urticae Koch (Acari: Tetranychidae)

Two-spotted spider mite, Tetranychus urticae Koch is the major pest of various plants worldwide. Now the control is dependent on the use of chemical pesticides. Plant compounds are recently known as biopesticides. Essential oil of Elettaria cardamomum was researched on repellent and oviposition inhibition of T. urticae. The LC₅₀ values of fumigant toxicity of this oil on adults and eggs of the two spotted spider mite were 7.26 and 8.82?μL/L air, respectively. Also LT₅₀ value of essential oil at 45?μL/L air was 23.86?h and LT₅₀ value of essential oil at 60?μL/L air was 9.01?h. In addition, different concentrations of the essential oil of E. cardamomum significantly affected oviposition deterrence and repellency of adults. The results of this study indicated that essential oil of E. cardamomum may be considered as a biopesticide to control two spotted spider mites.     

Oviposition deterrence of shoots and essential oils of Minthostachys spp. (Lamiaceae) against the potato tuber moth

Abstract:  The potato tuber moth is a noxious pest of potato in stores, where the use of repellent plants is an environmentally sound alternative to the application of chemical pesticides. We evaluated the protective effect of native Minthostachys species (Lamiaceae) against tuber infestation by the potato tuber moth in a rustic store in Cusco, Perú. We covered potato tubers with dried shoots of Minthostachys spicata and Minthostachys glabrescens and compared tuber damage with a control treatment of maize straw. We also conducted a no-choice oviposition bioassay in the laboratory, testing the oviposition deterrence of essential oils of M. spicata , M. glabrescens and Minthostachys mollis at natural concentrations. We recorded the number of eggs laid by mated moths on filter paper treated with essential oils of each of the three species and on two control treatments: hexane and untreated blank. Finally, we tested for differences in oviposition deterrence among five full-sib families of potato tuber moth raised under identical conditions. We found that dried, chopped leaves and flowers of Minthostachys species reduced the percentage of tuber damage in stores in comparison with the control (5% vs. 12%), but no difference in protection was found between species. Essential oils at natural concentrations deterred moth oviposition, reducing the number of eggs laid by about 80% compared with the control treatments; again, there were no significant differences between Minthostachys species. Finally, whereas we detected among-family variation in oviposition on filter papers treated with essential oils, no difference was found in the number of eggs laid on control substrates. Therefore, there was genetic variation for oviposition deterrence in the potato tuber moth and resistance to repellent plants might evolve thereafter.     

Effect of methanolic extracts of neem (Azadirachta indica A. Juss) and bakain (Melia azedarach L) seeds on oviposition and egg hatching of Earias vittella (Fab.) (Lep., Noctuidae)

Abstract: The effects of methanolic extracts of neem ( Azadirachta indica ) and bakain ( Melia azedarach ) seeds on the oviposition behaviour and hatchability of eggs of Earias vittella were investigated under laboratory conditions. Treatments included 2, 4, 6, 8 and 10% concentrations of both extracts to compare with nimbecidine and untreated control. When able to choose, the adults preferred to lay a greater number of eggs on the untreated portion of the oviposition substrate (muslin) compared with the extract-treated portion. However, under no-choice conditions, higher concentrations of extracts caused proportionate reductions in the number of eggs laid. The extracts also manifested repellent activity by reducing the number of eggs laid even when the ovipositing females were not in direct contact with the extracts. Eggs laid on extract-treated oviposition substrate exhibited reduced hatching and marked adverse effects on hatching were noticed when the eggs were dipped in different concentrations of extracts. Adults fed on an extract-containing sucrose diet laid significantly fewer eggs with poor hatching. There was no egg laying when the moths were fed on a sucrose diet containing 6, 8 and 10% neem and 10% bakain extracts.     

Bioefficacy of plant essential oils against pulse beetles Callosobruchus spp. (Coleoptera: Bruchidae) in pigeon pea seeds with particular reference to Clausena pentaphylla (Roxb.) DC.

Thirty essential oils from higher plants of Gorakhpur Division (India) were evaluated at 0.36?μl/ml against two pulse beetles, Callosobruchus chinensis L. and C. maculatus F., causing infestation of pigeon pea seeds during storage. Clausena pentaphylla oil was more effective and exhibited absolute repellency against both the insects followed by Ocimum canum, Salvia plebeia and Zingiber zerumbet oils. Among these four oils, C. pentaphylla oil was most toxic and showed 100% mortality of both the insects at 10-μl dosage and 24-h exposure (LD₅₀?=?2.7?μl for C. chinensis & 2.4?μl for C. maculatus). Physical factors, viz. temperature, storage and autoclaving, did not cause any adverse effect on the toxicity of Clausena oil. During in vivo investigation, the oil protected 1?kg of pigeon pea seeds completely without reducing weight loss and seed damage up to 6?months when stored in gunny bags and glass containers. The oil was standardised by determining its various physicochemical properties. Thus, C. pentaphylla oil can be judiciously exploited as herbal insecticide against pulse beetles of pigeon pea seeds during storage.     

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.