Letteratura scientifica selezionata sul tema "Bacillus thuriengiensis"

Evaluation of six insecticides viz., Azadiractin1% (1000ppm) Neem oil, Baeuveria bassiana 1% WP, Bacillus thuriengiensis var kurstaki 5% WP, Metarhizium anisopliae 1.0% WP, Verticillium lecanii 1.15% WP and Ha NPV 250 LE were evaluated against Gram Pod Borer (Helicoverpa armigera Hubner) larvae. The Gram Pod Borer (GPB) larval population was counted on 5 randomly selected plants at 24 hr. before spray and at 3, 7 and 10 days after spray. The two-years experiment was conducted during Rabi 2018-19 and 2019-20 at the Rehti Farm of school of Agriculture, Mhow, experimental field of Department of Entomology, BRAUSS, (MP). All the biopesticides significantly reduced the GPB larval population. The Pooled GPB population varied from 2.30 to 2. 50 larvae/plant during Rabi season one day prior tothe first spray. The population was significantly lower with Bacillus thuriengiensis var kurstaki 5% WP, followed by Ha NPV 250 LE, Baeuveria bassiana 1% WP, Metarhizium anisopliae 1.0% WP and Azadiractina 1% (1000ppm) Neem oil, these five biopesticides are showing best management effects on the GPB larvae and pod damaging per cent and remain, and least effective treatment was Verticillium lecanii 1.15% WP. The maximum reduction of larval population and pod damaging per cent. In Rabi season, the highest chickpea grain yield was obtained with Bacillus thuriengiensis var kurstaki at 5% WP.

Adverse effect of moisture on some microbial insecticides such as Halt (Bacillus thuriengiensis var kurstaki, B.t.k.- 55000 S.U./mg), Biolep (B.t.k.- 32000 I.U. /mg), Vertimec (product of Streptomyces avermitilis - Avermectin1.8% w/v) and Bassina (formulation of Beauvaria bassiana-1 x 107 spore / ml) were studied against third instar larvae of mulberry silkworm, Bombyx mori L. under four levels of relative humidity ( 30%, 60%, 80% and 90% R.H.) and constant temperature (20 0 C ± 2 0 C). The biocide avermectin at 1000 ppm caused 96.66% and 95.00% mortality after 72 h of treatment at 80% and 90% relative humidity respectively. Whereas, halt and biolep caused 95.00%, 90.00% and 81.66%, 80.00% mortality after 72 h at the two respective humidies level. Through fungal formulation of B. bassiana proved to be less harmful against B. mori at 30% and 60% R.H. it inflicted 40 – 43.33% mortality at higher moisture level (>70% R.H.). Relative humidity was found to play a major role towards pathogenecity of all the tested microbials against B. mori. Increasing mortality was recorded with increase in days after treatment and maximum effect was noticed at 80% R.H. The overall effect followed the same trend for all the microbial insecticides, and the observed descending order was Avermectin > Halt > biolep > B. bassiana at four levels of relative humidity, respectively.

Abstract Canadian and United States (US) insect resistance management (IRM) programs for lepidopteran pests in Bacillus thuriengiensis (Bt)-expressing crops are optimally designed for Ostrinia nubilalis Hübner in corn (Zea mays L.) and Chloridea virescens Fabricius in cotton (Gossypium hirsutum L.). Both Bt corn and cotton express a high dose for these pests; however, there are many other target pests for which Bt crops do not express high doses (commonly referred to as nonhigh dose pests). Two important lepidopteran nonhigh dose (low susceptibility) pests are Helicoverpa zea Boddie (Lepidoptera: Noctuidae) and Striacosta albicosta Smith (Lepidoptera: Noctuidae). We highlight both pests as cautionary examples of exposure to nonhigh dose levels of Bt toxins when the IRM plan was not followed. Moreover, IRM practices to delay Bt resistance that are designed for these two ecologically challenging and important pests should apply to species that are more susceptible to Bt toxins. The purpose of this article is to propose five best management practices to delay the evolution of Bt resistance in lepidopteran pests with low susceptibility to Bt toxins in Canada and the US: 1) better understand resistance potential before commercialization, 2) strengthen IRM based on regional pest pressure by restricting Bt usage where it is of little benefit, 3) require and incentivize planting of structured corn refuge everywhere for single toxin cultivars and in the southern US for pyramids, 4) integrate field and laboratory resistance monitoring programs, and 5) effectively use unexpected injury thresholds.

A leaf dip technique of bioassay for mortality of DBM larvae was conducted in laboratory condition with room temperature of 25±2°C, relative humidity of 80±3% and 13:11 ratio of Light: dark period at Department of Entomology, Agriculture and Forestry University, Rampur, Chitwan with three replication and eight treatments; i.e. i) Lipel (Bacillus thuriengiensis var. kursataki) 2gm/l, ii) Racer (Beauveria bassiana 1.15% WP) 2gm/l, iii) Derisom (Fractions of Derris indica) 2ml/l, iv) Anosom (Extracts of Annona spp. 1%) 2ml/l, v) Neemix (Neem oil 60% w/w, Azadiractin content less than 300 ppm) 2ml/l, vi) Anthsuper (Chloropyrifos 16% A.I. + Alphacypermethrin 1%EC (w/w) 2ml/l, vii) cow urine (1:5 with water) and viii) control (water spray) in Completely Randomized Design (CRD). The larval mortality was taken after 3, 9, 21, 33, 57 and 93 hours after the treatment application. The larval mortality was found to be significantly higher in Anthsuper treated with 100% mortality of larvae within 33 hours after treatment application followed by cow urine, botanicals (Neemix, Derisom and Anosom) and microbials (Racer and Lipel) where the larval mortality over control was found to ranging from 10% to 47.57% during the experimental period. The larval mortality was 47.57% for Cow urine and Neemix followed by 38.14% for Anosom, 33.29% for Racer, 28.57% for Derisom and 19% for Lipel.it is concluded that chemical pesticide Anthsuper is superior for immediate control of the pest but considering the safety of environment and human health; for long-term control of the pest botanicals and microbials would be more efficient.

The study aimed to use integrated control factors to control the life aspect of whitefly on crops and evaluate the efficiency of chemical and biological pesticides against pests. Chemical pesticides were sprayed on the leaves. Alafsket chemical pesticide recorded the highest mortality rate with the increase in the period of exposure to the pesticide, as it recorded mortality (5-15) days from the treatment of the plant with the pesticide. All pesticides were used on the plant with three concentrations of Baronas the treatment - Oxymatrin to test the effectiveness of the pesticide against the insect, and the chemical pesticides used (Alafsket - the corrected percentage mortality for egg mortality when using the Afiskat pesticide after five days of treatment reached 94.4 compared to the rest of the other chemical treatments. Either in the primary nymphal stages, the offset pesticide recorded corrected mortality within five days of treatment, with an average of 95.2. As for the adult experience, the corrected percentage of mortality during three days of treatment was 86.6. As for the biological pesticides used in the experiment (Bacillus thuriengiensis - Beauveria bassiana - Entomopathogenic nematodes for both sexes - Heterohabditis sp - Steinernema sp- Basilomyces lilacinus) The treatment results of the used biocides were revealed by the superiority of the suspension of insect-pathogenic nematodes of both sexes in giving them high mortality in eliminating the treated insect stages. The results of the treatment for the first stages of the nymphs were recorded with the superiority of the nematode suspension, which gave corrected mortality for the nymphs amounted to 93.6 within five days of treatment. As for the adult experience, the nematode suspension had higher mortality than other biological treatments. The adult mortality was 77.7 within three days of treatment

Pistachio (Pistacia vera) was successfully introduced into California and initially touted as a tree nut crop with no disease or insect pests. Unfortunately, these expectations were dashed as a number of diseases and pests followed commercial plantings, making plant protection practices integral to production. Verticillium wilt (Verticillium dahliae) devastated early plantings but is now controlled with the use of resistant rootstocks. Botryosphaeria blight (Botryosphaeria dothidea) and alternaria late blight (Alternaria alternata) are recently arrived foliar fungal diseases that blight fruit clusters and defoliate trees, respectively, and multiple fungicide applications are needed for control. The conversion to low volume irrigation systems, specifically to drip or buried drip, has reduced disease. Pruning out botryosphaeria blight infections has reduced overwintering inoculum and disease, while current research aims at accurately predicting infection events to increase fungicide efficacy. A number of hemipteran insect pests have been associated with epicarp lesion: spring treatments have been replaced with dormant carbaryl and oil applications which are less toxic to beneficial insects while controlling phytocoris (Phytocoris californicus and P. relativus) and soft scale pests. Early season insect damage can be tolerated because trees compensate by maturing a higher percentage of remaining fruit kernels. Some mirid (Calocoris spp.) pests can be effectively reduced by eliminating alternate hosts in an effective weed control program. If lygus (Lygus hesperus) populations are present, weeds should not be disturbed from bloom until shell hardening to prevent movement by insects into the trees where feeding can result in epicarp lesion. Stink bugs (Pentatomidae) and leaffooted bugs (Leptoglossus clypealis and L. occidentalis) can penetrate the hardened shell and cause internal nut necrosis along with epicarp lesion. Trap crops are used to monitor pest populations in order to develop treatment thresholds. Degree-day based timing of treatments increase insecticide efficacy for the control of navel orangeworm (Amyelois transitella) and obliquebanded leafroller (Choristonuera rosaceana), but navel orangeworm populations are more effectively managed by destroying unharvested over wintering fruit. Bacillus thuriengiensis sprays, liquid-lime-sulfur, and biological control show promise in controlling obliquebanded leafroller.

Abstract Background Mulberry silkworm, Bombyx mori L. is one of the most economically important insect because its production of silk which interfere with many important industries. Diseases of the silkworm, B. mori such as viral, bacterial, fungal and protozoan pathogens seriously affect their cocoon production. Bacterial and fungal pathogens independently cause the highest cocoon loss, so the use of botanicals is considered an important strategy to control diseases of silkworm. Results The artificially infected silkworm, B. mori larvae with Bacillus thuriengiensis when treated with concentrations of 2 and 3% of black seed and basil leaves extracts increased significantly larval weight and decreased larval mortality. In addition, 3% basil leaves extract and 1% of black seed increased pupal weight. Cocoon weight and cocoon shell weight increased significantly by 3% basil leaves extract treatment. All tested concentrations of black seed extract increased the silk ratios of the resulted cocoons as compared to the infected control. For technological parameters, all tested extracts at 3% concentration caused the highest silk filament length; meanwhile control larvae recorded the highest silk filament weight and size. Regarding the mulberry silkworm, B. mori artificially infested with conidial solution of Beauveria bassiana when treated with all concentrations of the tested plants showed an enhancement in larval weight, pupal weight, cocoon weight, cocoon shell weight, silk filament length, and filament weight and reduced the larval mortality percentage. The highest silk filament size were recorded for the control group. Conclusions Tested concentrations of Morus alba, Ocimum basilicum leaves extracts and Nigella sativa seeds extract have suppressed the bacterial and fungal disease spread when used three times through both 4th and 5th larval instars. Moreover, the biological characters and technological traits enhanced by using of these extracts, so it can be used in sericulture for improving cocoon crop quality and quantity.

Le groupe Bacillus cereus (B. cereus) regroupe des bactéries Gram positives issues de l’environnement. Ces bactéries sont capables de sporuler quand les conditions sont défavorables. Les membres de ce groupe peuvent être impliqués dans des intoxications alimentaires représentant ainsi la troisième cause d'intoxication alimentaire en Europe et la deuxième en France. L’espèce B. thuringiensis (Bt) appartient au groupe B. cereus et se caractérise par la production de cristaux parasporaux contenant des toxines Cry insecticides avec une forte spécificité d’action. Ainsi, les spores et les cristaux de Bt sont utilisés comme bioinsecticides pour lutter spécifiquement contre les larves de lépidoptères ravageurs. Les produits à base de Bt représentent plus de 50 % de marché mondiale des biopesticides. Une fois les spores et les cristaux ingérés par un organisme cible (les larves de lépidoptères), les toxines Cry contenues dans le cristal sont libérées et détruisent l'épithélium intestinal. Ensuite, le passage et la germination des spores dans l'hémolymphe entraînent une mort rapide du ravageur par septicémie. L’utilisation accrue de ces bioinsecticides Bt pose la problématique des risques potentiels engendrés sur les organismes non ciblés.En utilisant le modèle Drosophila melanogaster (un organisme non-cible de Bt), il avait été précédemment montré que les formes végétatives de Bt sont rapidement éliminées de l'intestin. Cette élimination est corrélée avec l'activation de la réponse immunitaire innée locale. Cependant, des études disparates suggéraient que les spores de Bt pouvaient persister dans les intestins des mammifères. Afin d’étudier le comportement de ces spores dans l'intestin des organismes non ciblés et l’implication de la réponse immunitaire innée, j’ai utilisé deux modèles de laboratoire : Drosophila melanogaster et la souris. En premier lieu, j'ai pu montrer qu’après une ingestion ponctuelle, les spores persistent jusqu'à 10 jours dans l'intestin moyen des drosophiles et au moins 5 jours dans l’intestin grêle des souris. Ce résultat m’a conduit à étudier le devenir de ces spores dans l’intestin. Pour cela, j'ai utilisé un outil généré au laboratoire où les spores fluorescent en rouge qui une fois germées en cellules végétatives acquièrent une fluorescence verte. En utilisant ces spores marquées, j'ai montré que ces dernières s'accumulent et germent préférentiellement dans les parties postérieures de l’intestin moyen de drosophile et de l’intestin grêle de souris. J’ai ensuite confirmé ces résultats qualitatifs par une approche quantitative en dénombrant spores et bactéries végétatives dans les différentes régions de l’intestin. Ainsi, toutes mes données suggèrent que la réponse immunitaire innée au niveau de la région postérieure de l’intestin moyen/grêle est inefficace pour éliminer rapidement les spores et les bactéries germées.Ensuite, je me suis donc focalisée sur la réponse immunitaire innée locale. Dans l'intestin moyen de la drosophile, cette réponse est localisée principalement dans les régions antérieures et se manifeste par une production d’espèces réactives de l’oxygène (ROS) et de peptides antimicrobiens (AMP). Mes résultats montrent que contrairement aux cellules végétatives, les spores n’induisent pas la production de ROS et d’AMP par l’épithélium intestinale. Etonnamment, j’ai même observé que la production d’AMP est réprimée. J’ai ensuite démontré que l’ingestion de spores induit l’expression de gènes codant pour des régulateurs négatifs (PGRP-SC1, -SC2 et -LB) de la réponse immunitaire innées dans la région postérieure de l’intestin moyen. Enfin, en utilisant des combinaisons de mutants des deux voies de signalisation immunitaires, Imd et Toll, j’ai pu caractériser pour la première fois leur coexistence dans l'intestin moyen de la drosophile et leur contribution de manière additive ou synergique aux infections par des spores du groupe B. cereus
The Bacillus Cereus (B cereus) group consists of Gram-positive bacteria, commonly isolated from the environment. Members of the B. cereus group are spore-forming bacteria commonly associated with food poisoning and intestinal infections and represent the third cause of food poisoning in Europe and the second in France. The most-studied members of this group are B. anthracis, B. cereus sensu stricto (Bc), and B. thuringiensis (Bt) that are well known for their pathogenic activity. Bt is characterized by the production, during its sporulation, of a crystal containing insecticidal Cry toxins. Thanks to this entomopathogenic activity, bioinsecticides based on spores and crystals of Bt are used to specifically kill lepidopteran pests. Bt bioinsecticides represent more than 50% of the global market share of biopesticides. Upon ingestion of Bt bioinsecticides (spores and toxin crystals), Cry toxins are released from the crystal and destroy the insect gut epithelium allowing spores to invade the internal milieu. Then spores’ germination in the hemolymph lead to the pest death by septicemia in less than 3 days. However, the increasing environmental dispersion of Bt products raises the question about their potential risks for non-target animals.Using Drosophila melanogaster (a non-target organism), it has been previously shown that Bt vegetative cells are rapidly cleared from the intestine. This elimination is due to the activation of the local innate immune response. However, few studies suggest that Bt spores can persist in human and rodent intestines. To understand why and how Bt/Bc spores persist in the gut of non-target organisms and the implication of the innate immune response in fighting spores, I have used two powerful models: Drosophila melanogaster and mice. First, I have shown that Bt/Bc spores can persist, after acute ingestion, up to 10 days in the Drosophila midguts and at least 5 days in mice small intestines., Then, using an innovative tool, generated in my lab, consisting of red fluorescent spores that switch in green fluorescent once germinated (corresponding to vegetative bacteria), I have shown that spores accumulate mainly in the posterior midgut of Drosophila and the posterior small intestine of mice where they can further germinate. Then, I confirmed these data using quantitative monitoring of spores vs. vegetative bacteria accumulation in vivo in the intestines of Drosophila and mice. Altogether, my data suggest that, in the posterior regions of the Drosophila midgut (and the small intestine of mice), the innate immune response is inefficient to promptly eliminate spores and germinated bacteriaIn Drosophila midgut, the local innate immune response (i.e. the production of Reactive Oxygen Species (ROS) and Anti-Microbial Peptides (AMPs)) is mainly mounted in the anterior regions. I have shown that, unlike vegetative cells, spores do not trigger ROS and AMPs production. Strikingly, I have even observed that spores inhibit AMPs production. Interestingly, I have found a transcriptional induction of negative regulators (e.g. PGRP-SC1, -SC2, and -LB) of the immune signaling pathways in the posterior region of the midgut in response to spore ingestion. Then, using combinations of mutants of the two immune pathways, Imd and Toll, I have been the first to demonstrate that both immune pathways coexist in the Drosophila midgut, and may contribute either additively or synergistically to fight spore infections

Orientador : Iracema de Oliveira Moraes
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: O uso de inseticidas químicos no controle de pragas da agricultura e grãos armazenados nem sempre se mostrou adequado. Como alternativa, vem sendo sugeridos métodos biológicos, como o uso de microorganismos entomopatogênicos, altamente específicos. Entre esses, a bactéria Bacillus thurigiensis tem se destacado tanto pelo volume de trabalhos publicados, como pelo interesse comercial que representa. Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital.
Abstract: Recently it has been recognized that the chemical insecticides are by no means, the ideal solution for the control of insects that inflict the heaviest losses on agricultural crops. Thus, the introduction of highly specific biological means for insect control has offered a sound alternative to chemical insecticides. Among the best studied species is the commercially important Bacillus thuringiensis. Note: The complete abstract is available with the full electronic document.
Doutorado
Doutor em Engenharia de Alimentos