Confused Flour Beetle Tribolium Confusum Research Articles

The effect of two isolates of Beauveria bassiana (Bals.) Vull. on the larvae of confused flour beetle [Tribolium confusum du Val., 1863 (Coleoptera: Tenebrionidae)

The confused flour beetle cause economic losses in stored products, especially in products obtained from wheat. Although using insecticides against storage pests is an effective method, their frequent and continuous use can lead to resistance and toxicity issues in non-target organisms. In this study, the effect of local Beauveria bassiana isolates (BMAUM LD.2016 and BMAUM M6-4) on the 3rd instar larvae of confused flour beetle (Tribolium confusum) was determined under laboratory conditions. As a result of the experiment, both isolates of B. bassiana were found to be more effective on the larvae in the spraying method compared to the dipping method. In the spraying method, mortality rates on the 9th day were 72% in BMAUM LD.2016 isolate, 34% in the dipping method, respectively. Mortality rates of BMAUM M6-4 isolate were recorded as 96% in the spraying method and 8% in the dipping method. In the spraying method, the mortality date (LT50) was determined as 6.09 days for BMAUM LD.2016 isolate and 3.90 days for BMAUM M6-4 isolate. The LT50 value could not be calculated in the dipping method, since the mortality rates were below 50% for both isolates. BMAUM M6-4 isolate caused higher mortality in larvae than BMAUM LD.2016 isolate. As a result, B. bassiana isolates have shown a high level of effectiveness against T. confusum, demonstrating that they can be used as isolates for insect control.

Comparative analyses of six cytochrome P450 genes and their roles in differential insecticide susceptibilities between the red flour beetle and the confused flour beetle

The red flour beetle (Tribolium castaneum Herbst) and the confused flour beetle (Tribolium confusum Jacquelin du Val) are closely related species commonly infesting stored grains and milled grain products. Although the same insecticides are used to control both species, their susceptibilities to those insecticides often vary considerably. To explore possible contributions of cytochrome P450 (CYP) genes to the differential insecticide susceptibilities between T. castaneum and T. confusum, we selected six CYP orthologous genes to explore their possible contributions to differential insecticide susceptibilities to each of three commonly used insecticides (dichlorvos, pyrethrins, and esfenvalerate). After the expression of each CYP gene was suppressed by RNA interference (RNAi) in late larvae, we examined larval susceptibility to each insecticide. Our results showed that although T. castaneum were more susceptible to dichlorvos than T. confusum, none of these CYP genes appeared to play any significant role in differential dichlorvos susceptibility between the two species. In contrast, there were no significant differences in larval susceptibility to pyrethrins between the two species. However, suppression of CYP4BR3 expression increased larval susceptibility to pyrethrins in T. castaneum at 24 and 72 h after the insecticide exposure, but not in T. confusum. Furthermore, RNAi-mediated suppression of CYP4G7, CYP9Z5, CYP4BR3, and CYP345A1/6 significantly increased larval susceptibility to esfenvalerate in T. castaneum but not in T. confusum at 72 h. In addition, the suppression of CYP4G7 expression increased larval susceptibility to esfenvalerate at 96 h in both species. These results suggest that although CYP4G7 may play some role in esfenvalerate susceptibility in T. confusum, CYP4G7, CYP9Z5, CYP4BR3, and CYP345A1 significantly contribute to differential esfenvalerate susceptibilities between two Tribolium species. This study represents the first study to reveal molecular mechanisms causing differential insecticide susceptibilities between the two Tribolium species.

Fumigant toxicity of some essential oils and eucalyptol on different life stages of Tribolium confusum (Coleoptera: Tenebrionidae)

ABSTRACT Essential oils of aromatic plants have a high potential for the development of alternative insect pest management strategies. Especially for the control of stored product pests, alternative methods to replace synthetic insecticides are urgently needed. We evaluate the fumigant toxicity of Myrtus communis, Eucalyptus globulus, Syzygium aromaticum, Thymus saturejoides essential oils, and the main natural compound of two of them, eucalyptol, on different life stages of the confused flour beetle (Tribolium confusum) under laboratory conditions. Whereas eucalyptol and the essential oils of M. communis and E. globulus have rather strong toxic effects on all developmental stages, apart from the eggs of T. confusum, the essential oil of S. aromaticum caused the highest egg toxicity. Our results indicate that eucalyptol or essential oils containing large amounts of this compound might be efficient as potential alternative control agents for T. confusum, but tests under more natural conditions need to be performed.

Assessment of some essential oils and their mixtures as materail repellents against the confused flour beetle, adult Tribolium confusum (du val) (Coleoptera: Tenebrionidae).

Repellency of the six essential oils (EOs), Clove (Eugenia aromaticum), Aloe (Aloe vera), Lemon (Citrus limon), Camphor (Euca-lyptus camaldulensis), Mint (Mentha spicata), Marjoram (Origanum vulgare) were evaluated against adult of the confused flour beetle Tri-bolium confusum, by allowing adults to choose between untreated filter paper halves with 1 -2g white flour or treated with different concen-trations of the oils and their mixture at three different exposure times. In individual oils ex-periments, Eucalyptus camaldulensis was found to be the best effective of repellent effi-cacy, followed by Mentha spicata and Eugenia aromaticum. Citrus limon and Aloe vera have moderate repellent efficacy. Results of combi-nation effective showed that mixtures' repel-lant activity. It has been shown that the most powerful mixture of Clove + Mint repels activ-ity against adults with Lemon + Aloe, Lemon + Marjoram, Lemon + Mint, and Mint + Aloe during the entire exposure period, while Lemon + Camphor and Camphor + Mint lost repellent activity after 24 hours.

Essential Oil-Based Nano-Biopesticides: Formulation and Bioactivity against the Confused Flour Beetle Tribolium confusum

Post-harvest pest control can rely on few approved pesticides and tools; hence, there is a rising interest in new sustainable, eco-friendly approaches. In this study, eight commercial essential oils (EOs) (anise Pimpinella anisum, artemisia Artemisia vulgaris, fennel Foenicum vulgare, garlic Allium sativum, lavender Lavandula angustifolia, mint Mentha piperita, rosemary Rosmarinus officinalis, and sage Salvia officinalis) were selected for their bioactivity and commercial availability, and then formulated in nano-emulsions. Repellency and acute toxicity of the developed nano-formulations were tested against a key stored product pest, Tribolium confusum (Coleoptera: Tenebrionidae). All the developed nano-emulsions presented optimal physical characteristics (droplet dimension = 95.01–144.30 nm; PDI = 0.146–0.248). All the formulations were repellent over time tested against adult beetles, in area preference bioassays. The best repellent was the anise EO-based formulation (RC50 = 0.033 mg). Mortality values from cold aerosol trials showed that the majority of tested EOs caused immediate acute toxicity, and garlic EO nano-emulsion caused the highest mortality of T. confusum adults (LC50 = 0.486 mg/L of air). EO-based nano-insecticides, used as cold aerosol and gel, are promising control methods against stored product pests, which can be integrated and combined with other sustainable biorational approaches.

Isofuranodiene-based nanoemulsion: larvicidal and adulticidal activity against tenebrionid beetles attacking stored wheat

The resistance of insect populations to the existing insecticides grows fast due to their continuous use. Thus, the need for new and effective formulations is increasing. Isolated compounds of botanical origin may represent a promising solution for green pest management strategies. In this study, isofuranodiene derived from Smyrnium olusatrum L. (Apiales: Apiaceae) essential oil (EO), was nanoemulsified (3% w/w) to treat wheat kernels with two concentrations (500 and 1000 ppm) against adults and larvae of three tenebrionid beetles attacking stored products, the red flour beetle, Tribolium castaneum (Herbst), the confused flour beetle Tribolium confusum Jacquelin du Val, and the yellow mealworm beetle, Tenebrio molitor L. Mortality rates were calculated after 4, 8 and 16 h and 1, 2, 3, 4, 5, 6 and 7 days. The isofuranodiene-based nanoemulsion (NE) exhibited high adulticidal effects against T. molitor, and larvicidal activity against T. castaneum and T. confusum, reaching 98.6, 97.4 and 93.5% at 1000 ppm after 7 days of exposure, respectively. On the other hand, the NE caused low mortality rates on adults of T. castaneum and T. confusum, as well as on larvae of T. molitor, not exceeding 26.2, 10.0 and 15.6% at 1000 ppm, 7 days post-exposure, respectively. Overall, the 3% (w/w) isofuranodiene-based NE developed here has a significant potential to protect stored wheat from tenebrionid beetle infestations.

Efficacy of nano-formulated certain essential oils on the red flour beetle Tribolium castaneum and confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae) under laboratory and storage conditions

AbtractBackgroundThe confused flour beetles Tribolium confusum (Jacquelin) and red flour beetle Tribolium castaneum (Herbst) are widespread insects found in the stores and homes that attack many stored foods in several commodities. They are controlled by synthetic chemical insecticides. The natural oils give good results in controlling these pests and decreasing its infestations. The natural essential oils have a low effect on the human, non-target insects, and do not pollute the environments. This research is an alternative approach to naturally control these two stored product pests.MethodsNano-formulations of four essential oils, namely, coriander, black seed, caraway oil, and Janesville were tested against T. confusum and T. castaneum in the laboratory and stored conditions. Encapsulation method by the technology of polymerization was followed. The nano-oils were tested at the concentrations of 0.5% against the 3rd larval instars. Cumulative percentages of mortality was determined after 7 days of the first applications. The effect of nano-oils on oviposition was carried out by spraying 2 g of foams of the tested oils and their nano-formulations mixed with 100 g of wheat.ResultsThe results obtained showed that the percentage of larval mortality of T. confusum and T. castaneum increased with an increase in the treatment concentrations. Larvae of T. confusum were more susceptible to the treatments than T. castaneum larvae. Nano Janesville oil was more effective than that of coriander or black seed oil. Fecundity and adult emergence percentage are highly suppressed by nano-formulations of coriander, black seed, or Janesville oils under storage conditions, compared to those of the controls or non-nano-oils.The results suggested that nano Janesville can be used as a valuable tool in pest management programs of T. confusum and T. castaneumConclusionThe results of this work indicate that some essential oils might be helpful management of pests in the stores because of their fumigant and odor action. Essential oils of plant origin contain active ingredients that are effective against many insects. Nano-formulations of essential oils, through controlled release, prevent rapid vaporization and degradation and increase the stability of the oils. Treated foam, using coriander, Janesville, caraway, and black seed (habat al Baraka) oils, gave protection against the red flour beetles Tribolium castaneum and confused flour beetle Tribolium confusum.

Studying the Effectiveness of Some Plant Powders on the Biological Activities of the Confused Flour Beetle Tribolium confusum du Val (Coleoptera: Tenebrio-nidae).

This study aims to test the biological effect of three plant powders of (black pepper fruit Piper nigrum L., nutmeg seeds Myristica fragrans Houtt and bay leaf Laurus nobilis L.) when mixed with wheat flour at concentrations of; 0.2, 0.5, 0.75, 1 and 1.5 % (w/w) against the confused flour beetle Tribolium confusum. Results showed that the black pepper fruit caused a decrease in the production of larvae that reached 65.36%, while the nutmeg seeds powder caused a decrease of 50.93% compared with the bay leaf powder, which caused a decrease of 38.20%. The results also showed a decrease in the first generation progeny (F1) that reached 90.75% and 75.34% due to the treatment with the black pepper fruit and the nutmeg seeds powders respectively. However, the bay leaf powder was less effective, with only a decrease of 30.13%.

Biodegradation of plastic wastes by confused flour beetle Tribolium confusum Jacquelin du Val larvae

Biodegradation of plastic wastes by confused flour beetle Tribolium confusum Jacquelin du Val larvae

The Effect of Grain Type on Virulence of Entomopathogenic Fungi Against Stored Product Pests

Fungal virulence is multifaceted and dependent on multiple abiotic factors. The present study represents an investigation of the effect of one such abiotic factor, that of the grain type, on the insecticidal action of three entomopathogenic fungal species, Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae), Metarhizium anisopliae (Metschinkoff) Sorokin (Hypocreales: Clavicipitaceae) and Isaria fumosorosea Wize (Hypocreales: Clavicipitaceae) on larvae of the three very common and destructive stored product pests: the khapra beetle (Trogoderma granarium Everts) (Coleoptera: Dermestidae), the confused flour beetle (Tribolium confusum Jacquelin du Val) (Coleoptera: Tenebrionidae) and the Mediterranean flour moth (Ephestia kuehniella Zeller) (Lepidoptera: Pyralidae). To this end, we selected four different grains, i.e., Triticum aestivum L. (Poales: Poaceae), Oryza sativa L. (Poales: Poaceae), Arachis hypogaea L. (Fabales: Fabaceae) and Vicia faba L. (Fabales: Fabaceae). Bioassays were carried out in the lab, where experimental grains were sprayed with 1 mL of conidial suspension (108 conidia/mL) from each isolate. Mean mortality, median survival time and weight loss of seeds were estimated for each species. Our results suggest that the differences in the efficacy of entomopathogenic fungi were dependent both on the isolates and the grain. The grain type as a factor is equally important to other abiotic factors.

Comparison of the effects of multiple variables on the levels of infection of the rat tapeworm, Hymenolepis diminuta, in its intermediate host, the confused flour beetle Tribolium confusum.

The interaction of the rat tapeworm, Hymenolepis diminuta, with its intermediate beetle host, Tribolium confusum, is a well-studied model system. However, there is so much variation in the methods and designs of the studies that it is difficult to draw comparisons. This study simultaneously compared several aspects of the infection protocol including beetle age, sex, density and mating status; parasite egg condition, infection environment humidity and the times for the three steps of infection: starvation, feeding and post-feeding development. Although statistically limited by low prevalence and intensity levels, we were able to detect the relative effects of the variables. The effects of these variables on prevalence (percent infection) and intensity (mean number of cysticercoids) do not necessarily correlate with each other. Egg condition, reduced starvation times, higher beetle density and longer development times reduced prevalence. However, differences in intensity were only detected with older beetles. When coupled with survivorship data, our study found that our current infection protocol is optimal for infection success. However, the results suggest extending the study to other intermediate hosts and the inclusion of additional variables.

Differential susceptibilities of two closely-related stored product pests, the red flour beetle (Tribolium castaneum) and the confused flour beetle (Tribolium confusum), to five selected insecticides

The red flour beetle (Tribolium castaneum Herbst) and the confused flour beetle (Tribolium confusum Jacquelin du Val) are among the most commonly encountered insects infesting stored food, but their susceptibilities to different insecticides often differ significantly, which complicates efforts to manage populations in milling and processing facilities. In this study, the susceptibilities of T. castaneum and T. confusum late-stage larvae to five selected insecticides, esfenvalerate, pyrethrins, dichlorvos, methoprene and pyriproxyfen, were assessed with and without synergists using topical applications. In four-day bioassays (without flour) with dichlorvos, esfenvalerate and pyrethrins, T. castaneum larvae were less susceptible (low larval mortality) to dichlorvos and esfenvalerate than T. confusum, whereas the reverse was true for treatment with pyrethrins. Pre-treatment with one of three synergists, piperonyl butoxide (PBO, cytochrome P450 monooxygenase inhibitor), S,S,S-tributyl phosphorotrithioate (DEF, esterase inhibitor), or diethyl maleate (DEM, glutathione S-transferase inhibitor), suggested involvement of esterases in the detoxification of dichlorvos and pyrethrins, and cytochrome P450 monooxygenases in the detoxification of esfenvalerate in both species. Interestingly, pre-treatment with some synergists increased the toxicity of insecticides in only one species: DEM and DEF increased the toxicity of dichlorvos to T. castaneum, whereas only DEF increased dichlorvos toxicity to T. confusum. In 28-day bioassays with larvae treated with each of two insect growth regulators (IGRs), methoprene and pyriproxifen, T. confusum was the more tolerant species. All T. castaneum died in either the larval or pupal stages with either IGR. In contrast, only pyriproxyfen caused complete mortality in T. confusum larvae, and even the highest dose of methoprene allowed nearly 70% of T. confusum larvae to pupate, and 4.5% of adults to emerge. Our results show that although these two species are closely related, they display very different susceptibilities to different insecticides, and different metabolic detoxification mechanisms may contribute to their differential insecticide susceptibilities.

The Effects Of 2-Hydroxy Chalcone and its Derivative on The Larvae and Adults of Tribolium Confusum

2-Hydroxy Chalcone and its derivatives (compounds 1and 2) were used in a toxicity test on the larvae and adults of confused flour beetle Tribolium confusum (Du Val). Mortality tests were done by applying different concentrations (0.01, 0.02 and 0.04 ppm) on 2-Hydroxy Chalcone and its derivatives which were exposed by topical application with 5 µL of each compound and the data were recorded after 24 h of treatments. The mortality % of [7-Hydroxy-9-(pyridine-4-yl)-6H-benzo[C]chromen-6-one] in (compound 2) were 26.6, 50 and 76.67% and 16.67, 36.67 and 63.3% and 13.3, 23.3 and 36.6 % to 3rd, 5th instar larvae and adults, respectively. While in [ 3-thinyl-1-(2-hydroxynaphthyl) -1-propene] (compound 1), the mortality % were 23.3, 40 and 66.6% and 13.3, 30 and 56.6% and 6.6, 16.6 and 26.6 % to 3rd, 5th instar larvae and adults, respectively. The results indicated that (comp.2) was the most toxic one and (comp.1) was the least toxic to confused flour beetle when applied singly. The calculated LC50 values to (compound 2) were 0.019, 0.028 and 0.074 ppm to 3rd, 5th instar larvae and adults, respectively. While to (compound 1), the LC50 values were 0.025, 0.034 and 0.106 ppm to 3rd, 5th instar larvae and adults, respectively. The order of toxicity of the chemical compounds was 2 > 1. These chemical compounds can be used to control confused flour beetle.

Insecticidal efficacy of nano zeolite against Tribolium confusum (Col., Tenebrionidae) and Callosobruchus maculatus (Col., Bruchidae)

BackgroundStored-product insect pests are responsible for considerable quantitative and qualitative losses of agricultural products mainly cereals and legumes. The confused flour beetle Tribolium confusum and the cowpea weevil Callosobruchus maculatus are considered as the most destructive pests of stored grains and grain-derived products. In the present study nano zeolite (40–50 nm) was applied at different dose rates to wheat and cowpea to evaluate its insecticidal efficacy against both insects.ResultsInsect mortality was assessed after 1, 2, 3, 7, and 14 days of exposure for T. confusum and after 1, 2, and 3 days of exposure for C. maculatus. The mortality of T. confusum and C. maculatus adults exposed to wheat and cowpea seeds treated with nano zeolite was increased significantly with increasing dose and exposure intervals. The adult progeny production and the number of eggs laid were significantly decreased by increasing nano zeolite dose. In the present study, scanning electron microscope (SEM) was used to observe the adult insects exposed to nano zeolite-treated seeds. Nano zeolite attached all over the insect body with scratches and splits on the cuticle that lead to the loss of water through dehydration.ConclusionThe results indicated that nano zeolite, which is considered as nontoxic to the environment and safe for human consumption, can be used effectively with success as an integral part of programs for the protection of cereal grains from stored-product insect pests.

Effect of gamma ray irradiation on chemical composition, antioxidant, antimicrobial, and insecticidal activities of Thymus pallescens essential oil

The essential oils isolated by hydrodistillation from Thymus pallescens de Noé dried leaves exposed to γ-irradiation at dose levels of 0, 5, 10, 20, and 30 kGy were analyzed by gas chromatography–flame ionization detector (GC–FID) and GC–mass spectrometry (MS) and tested for their antioxidant, antimicrobial, and insecticidal activities. No qualitative change was observed in the chemical composition. Carvacrol (81.8–85.7%) was the most prominent component. Gamma-irradiation at 20 kGy affects quantitatively some components. Antioxidant activity was evaluated by four different test systems, namely, inhibition of lipid peroxidation (thiobarbituric acid reactive substance, TBARS), ferric reducing power, and scavenging of radicals DPPH• and ABTS•+. In all systems, irradiated oils at 20 and/or 30 kGy showed the most antioxidant efficiency. Overall, the antimicrobial activity conducted against seven microorganisms revealed no significant changes according to the radiation dose. Fumigation bioassays and contact method against confused flour beetle Tribolium confusum revealed that the oil irradiated at 20 kGy had highest insecticidal activity. The results showed that gamma-irradiation of T. pallescens could be not only beneficial safe decontamination perspective but also as an improvement factor of some of its properties.

Olfactory host location and host preference of Holepyris sylvanidis (Brèthes) (Hymenoptera: Bethylidae), a parasitoid of Tribolium confusum Jacquelin du Val and T. castaneum (Herbst) (Coleoptera: Tenebrionidae)

Parasitoids can suppress populations of their host and thus play a primary role in Integrated Pest Management. We studied foraging cues in Holepyris sylvanidis (Hymenoptera: Bethylidae), a larval parasitoid of Tribolium species, in a four-chamber olfactometer. H. sylvanidis is reported as a cosmopolitan parasitoid of Coleopteran including two major pests of stored products, the confused flour beetle Tribolium confusum and the red flour beetle T. castaneum. Our study reveals that the host complexes of both Tribolium species and different living host stages attract naive H. sylvanidis females, whereas no reaction was observed to uninfested substrates. Our findings may contribute to the development of biological control strategies of T. castaneum and T. confusum with parasitoids.

Scanning electron morphological studies of Tribolium confusum Jacquelin du Val (Coleopteran: Tenebrionidae)

BackgroundThe confused flour beetle Tribolium confusum Jacquelin du Val (Coleopteran: Tenebrionidae) is the most destructive pest of stored products worldwide. It is the most common pest of wheat flour.ResultsThis study describes and illustrates the larvae, pupae, and adults of T. confusum using scanning electron microscopy. The first larval instars are 5.0–5.1 mm long and 0.5–0.6 mm wide whereas the last larval instars are 5.75–6.9 mm long and 0.75–0.95 mm wide. Adults of T. confusum are reddish brown elongate beetles (4.0–4.5 mm in body length and 1.0–1.2 mm in width). Electron micrographs revealed the structure of the mouth parts during the larval, pupal, and adult stages as well as the structure of thoracic and abdominal appendages. Results indicated that the setiferous sex patches which were reported in males can often be used for sexing specimens. A specific feature of the first instar larvae of T. confusum is the extreme shortened antenna with a reduced number of antennomeres and the presence of well-developed and moderately long legs.ConclusionSEM examination may help us not only discover and understand new morphological details as the pits with spine on the elytra and the spikes on the membrane wings which will facilitate the identification of this species but also clarify the functions of various body parts.

Reproductive biology of Holepyris sylvanidis (Hymenoptera: Bethylidae)

Holepyris sylvanidis (Hymenoptera: Bethylidae) is reported as a cosmopolitan parasitoid of coleopteran including a major pest of stored products, the confused flour beetle Tribolium confusum. The reproductive biology, and hence biocontrol potential of H. sylvanidis is relatively little known. Here we describe and evaluate aspects of egg size, immature development, adult mating behaviour, pre-oviposition time, fecundity, host attack and use, and adult longevity. Our key findings are that ≈72% of presented T. confusum immatures presented to females were attacked and ≈39% of these were fed on destructively with the remainder oviposited onto. First instar host larvae and host pupae were only utilized for feeding, second and third instar larvae were commonly used for either feeding or oviposition while fourth, fifth and sixth instar hosts were almost exclusively used for oviposition. Females usually laid single egg clutches and their average lifetime fecundity was ≈16.5 eggs. Females regularly provisioned with hosts often ceased laying eggs up to several weeks before their death but continued to kill and feed on hosts during this period. Adult longevity was greatly enhanced by the provision of hosts (females) or by non-host food sources (males). We conclude that the inoculative biocontrol potential of H. sylvanidis is likely to be limited by a low realized fecundity and the combination with other control methods in an IPM-approach is needed. Its ability to find and kill hosts may make it more suitable for inundative deployment.

Host Habitat Volatiles Enhance the Olfactory Response of the Larval Parasitoid Holepyris sylvanidis to Specifically Host-Associated Cues.

Host foraging of parasitic wasps attacking insects living in stored food may be guided by volatile cues emanating from these postharvest products. However, little knowledge is available as to how habitat odor released from noninfested stored food affects the parasitoid's response to host-specific chemicals. In this study, we investigated the impact of wheat grist odor on the olfactory host search by the ectoparasitoid Holepyris sylvanidis This parasitoid attacks larvae of the confused flour beetle Tribolium confusum, a common pest of grain products. Olfactometer bioassays showed that female H. sylvanidis were attracted by volatiles released from host larval feces, whereas odor of noninfested wheat grist was neither attractive nor did it mask the host-indicating cues. We analyzed the odor of host larval feces and wheat grist by coupled gaschromatography-mass spectrometry and recorded the parasitoid's electroantennographic (EAG) responses to the detected volatiles. Two specifically host-associated components of the fecal odor, (E)-2-nonenal and 1-pentadecene, elicited strong EAG responses. Both components were attractive when tested individually, but less than larval feces. Attraction of parasitoids to these host-specific key compounds was enhanced by addition of (i) noninfested habitat substrate odor or (ii) a blend of 3 EAG-active (but not behaviorally active) volatiles that had been identified in odor of noninfested grist (benzaldehyde, 1-tetradecene, 1-hexadecene), but were also detected in the host fecal odor. The impact of these volatiles ubiquitously released in a food store by noninfested habitat substrate on the parasitoid's orientation to host-specific volatile cues is discussed.

Influence of Extraction Duration on the Chemical Composition and Biological Activities of Essential Oil of Thymus pallescens de Noé

Thymus pallescens de Noe essential oils were isolated from the plant’s dried leaves, by hydrodistillation, with different distillation times (30 min, 1, 2 and 3 h). The essential oils compositions and their antioxidant, antimicrobial and insecticidal activities were examined. The chemical compositions of the oils were determined by GC and GC-MS. The antioxidant capacity was tested by four complementary methods: thiobarbituric acid reactive substances, ferric reducing power and scavenging of radicals DPPH• (2,2-diphenyl-1-picrylhydrazyl) and ABTS•+ [2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid)]. The antimicrobial activity was tested against three bacteria, two gram-positive (Staphylococcus aureus and Bacillus subtilis) and one gram-negative (Escherichia coli) and one yeast (Candida albicans). The insecticidal activity against confused flour beetle Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) was evaluated using direct contact application and fumigant method. The predominant components in the oils were carvacrol (63.3–68.2 %), γ-terpinene (6.9–9.1 %), p-cymene (6.2–10.3 %) and thymol (6.5–7.5 %). The antioxidant activities were dependent on the time of hydrodistillation and the method used. The essential oils extracted for 30 min and 1 h were the most efficient against all the bacteria used. Toxicity tests against T. confusum showed that the oils isolated for 3 h and 30 min caused highest mortality with contact method and fumigant test, respectively. The results suggest that distillation time can determine the value of the oil designed to be applied to any biological material.