1,720,995 research outputs found
Plant-Growth-Promoting Bacteria (PGPB) against Insects and Other Agricultural Pests
No full textThe interest in using plant-growth-promoting bacteria (PGPB) as biopesticides is significantly growing as a result of the discovery of new properties of certain beneficial microbes in protecting agricultural crops. While several rhizobial species have been widely exploited for their ability to optimize plant use of environmental resources, now the focus is shifted to species that are additionally capable of improving plant health and conferring resistance to abiotic stress and deleterious biotic agents. In some cases, PGPB species may directly act against plant pathogens and parasites through a variety of mechanisms, including competition, protective biofilm formation, and the release of bioactive compounds. The use of this type of bacteria is in line with the principles of ecosustainability and integrated pest management, including the reduction of employing chemical pesticides. Several strains of Bacillus, Paenibacillus, Brevibacillus, Pseudomonas, Serratia, Burkholderia, and Streptomyces species have been the subject of specific studies in this direction and are under evaluation for further development for their use in biological control. Accordingly, specific case studies are presented and discussed
Associazione di nematodi entomopatogeni con batteri del suolo. Il caso di Steinernema feltiae.
No full textMentre l'azione bioinsetticida dei nematodi entomopatogeni (EPN) si basa tipicamente sulla simbiosi
con batteri “core”, come Photorhabdus e Xenorhabdus spp. è stata studiata l'associazione di un
nuovo ceppo “non-core” del batterio del suolo Pseudomonas protegens con stadi giovanili infettivi di
Steinernema feltiae. Tale associazione è risultata robusta e il batterio è apparso ben adattato
all'emocele degli insetti, essendo in grado di proliferare rapidamente dopo che anche una piccola
quantità di cellule vive (100 CFU) veniva inoculata in larvae di Galleria mellonella, causandone la
rapida morte. Il ruolo dei nematodi parassiti degli insetti come vettori di questi batteri è emerso
in esperimenti che hanno coinvolto diverse generazioni di larve di G. mellonella inoculate con
differenti dosi di nematodi. Specifici biosaggi di laboratorio hanno mostrato diversi livelli di virulenza
del batterio nei confronti di Lepidotteri e Ditteri. Sebbene P. protegens sembri di per se possedere
un potenziale intrinseco come entomopatogeno, l'instaurazione di un'associazione stabile con
nematodi entomoparassiti rappresenterebbe un vantaggio competitivo che segna un particolare
passo evolutivo per queste specie
Oral toxicity of Pseudomonas protegens against muscoid flies
No full textThe bioinsecticidal action of Pseudomonas protegens has so far been reported against some target insects, and the mode of action remains unclear. In this study, the pathogenicity potential of a recently isolated strain of this bacterial species against fly larvae of medical and veterinary interest was determined. Preliminary experiments were conducted to determine the biocidal action by ingestion against Musca domestica and Lucilia caesar larvae, which highlighted a concentration-dependent effect, with LC50 values of 3.6 and 2.5 × 108 CFU/mL, respectively. Bacterial septicaemia was observed in the body of insects assuming bacterial cells by ingestion. Such rapid bacterial reproduction in the hemolymph supports a toxin-mediated mechanism of action involving the intestinal barrier overcoming. In order to gain more information on the interaction with the host, the relative time-course expression of selected P. protegens genes associated with virulence and pathogenicity, was determined by qPCR at the gut level during the first infection stage. Among target genes, chitinase D was the most expressed, followed by pesticin and the fluorescent insecticidal toxin fitD. According to our observations and to the diversity of metabolites P. protegens produces, the pathogenic interaction this bacterium can establish with different targets appears to be complex and multifactorial
Multiple S-Layer Proteins of Brevibacillus laterosporus as Virulence Factors against Insects
No full textS-layers are involved in the adaptation of bacteria to the outside environment and in pathogenesis, often representing special virulence factors. Vegetative cells of the entomopathogenic bacterium Brevibacillus laterosporus are characterized by an overproduction of extracellular surface layers that are released in the medium during growth. The purpose of this study was to characterize cell wall proteins of this bacterium and to investigate their involvement in pathogenesis. Electron microscopy observations documented the presence of multiple S-layers, including an outermost (OW) and a middle (MW) layer, in addition to the peptidoglycan layer covering the plasma membrane. After identifying these proteins (OWP and MWP) by mass spectrometry analyses, and determining their gene sequences, the cell wall multilayer-released fraction was successfully isolated and used in insect bioassays alone and in combination with bacterial spores. This study confirmed a central role of spores in bacterial pathogenicity to insects but also detected a significant virulence associated with fractions containing released cell wall multilayer proteins. Taken together, S-layer proteins appear to be part of the toxins and virulence factors complex of this microbial control agent of invertebrate pests
Safety of the Entomopathogenic Fungus Beauveria bassiana for Wild and Laboratory-Reared Chrysoperla lucasina Strains
No full textThe need to reduce the impact of plant protection products on agroecosystems fosters the use of augmentative biological control involving the release of beneficial species into the field, the employment of entomopathogenic microbials, and the protection of naturally occurring biocontrol agents. This study aimed to investigate the compatibility of the entomopathogenic fungus Beauveria bassiana with the generalist insect predator Chrysoperla lucasina, in comparative experiments involving a laboratory-reared and a wild chrysopid strain. The larvae of the predators were exposed to different concentrations of fungal conidia up to a concentration of 107 conidia/mL by contact and ingestion. The treated insects showed only slight differences in terms of survival and immature development time compared to the untreated control insects. A significant decrease in the proportion of the male adults of C. lucasina that emerged from the laboratory-reared larvae that were exposed to higher concentrations of the fungus suggested a potentially different susceptibility between the sexes. A slightly lower adult emergence rate was observed in the wild strain, while no significant differences were recorded in the adult reproductive performance. These findings indicate that the B. bassiana strain ATCC 74040, at concentrations commonly used in the field, did not pose a significant risk to C. lucasina and can be safely used in combination with this predator for sustainable pest management
ENTOMOPATHOGENIC NEMATODES ASSOCIATION WITH SOIL-DWELLING BACTERIA: THE CASE OF STEINERNEMA FELTIAE
No full textThe symbiosis of entomopathogenic nematodes (EPNs) with bacteria in the genera Photorhabdus and Xenorhabdus is well known. However, other soil-dwelling bacteria can occasionally be isolated from EPNs collected from diseased larvae. Accordingly, through several studies, we have detected the presence of diverse bacterial species including isolates of Pseudomonas protegens and Serratia spp., in the body of different strains of the entomopathogenic nematode Steinernema feltiae. After documenting the presence of such bacteria inside the nematodes, both nematodes and EPN-associated bacteria were cultured, and bioassays were conducted to determine their potential against different insect targets. An isolate of P. protegens caused over 60% and 90% mortality of house fly and corn earworm larvae, respectively. These insecticidal effects were dose-dependent. The presence of the bacterium confers virulence to the nematode. According to our studies, it appears that these non-core bacteria can establish occasional or stable associations with S. feltiae
Susceptibility of Environmentally Friendly Sheep Wool Insulation Panels to the Common Clothes Moth Tineola bisselliella in Laboratory Assays
No full textIn this study the resistance opposed to Tineola bisselliella larvae by a commercial sheep-wool panel incorporating borate salts was determined under laboratory conditions. The susceptibility of clothes moth larvae to different concentrations of disodium octaborate tetrahydrate (DOT) incorporated in pure wool was also determined. The commercial wool panel showed a remarkable resistance to moth attack compared with pure untreated wool, and the damage to panel samples was limited to their surface. As a result of bioassays exposing larvae to pure wool treated with DOT, a concentration dependent effect was observed, achieving a good efficacy at an application rate between 40–100 mg/mL. This study highlights the need to protect wool-based construction material with appropriate insecticidal (antifeedant or repellent) substances and supports the development of eco-sustainable solutions
Sustainable Silage Maize Integrated Protection against the European Corn Borer <i>Ostrinia nubilalis</i> and the Corn Earworm <i>Helicoverpa armigera</i> Employing the Farm Irrigation System
No full textSilage corn is an important source of feed in animal husbandry, often affected by the feeding action of diverse corn borers that can compromise harvest quality and quantity. According to the need to reduce the use of chemical insecticides, the main purpose of this study was to evaluate the efficacy of different IPM programs comparing microbial (Btk and baculovirus) and chemical control methods, alone or combined, against O. nubilalis and H. armigera. Assessments were based on counting the number of larvae, inspecting plants superficially and inside the stem, and estimating the derived damages. All tested products proved to be effective in containing the density of these lepidopteran species, with microbial control agents having comparable efficacy in respect to the reference chemical substances (lambda-cialotrina and chlorantraniliprole), even if periodic treatment repetition was required to ensure over-time protection until harvest. Both Btk and HaNPV were successfully applied by the irrigation system during flowering and fruit development periods, when plant height did not allow the use of a tractor-mounted spray bar. This biocontainment approach appears to be sustainable and technically compatible with farm needs
Comparative laboratory and field study of biorational insecticides for Culicoides biting midge management in larval developmental sites
No full textAn appropriate management strategy of bluetongue vectors should include larvicidal treatments in their larval development sites utilizing active substances with low environmental impact. A selection of biorational insecticides with potential against dipteran larvae was assayed in the laboratory against field collected Culicoides larvae including C. cataneii, C. circumscriptus, and C. imicola, determining their median lethal concentrations in water and mud/water substrate. The efficacy of formulations containing the insect growth regulators pyriproxyfen and cyromazine, the botanical insecticide azadirachtin, and the entomopathogenic bacteria Bacillus thuringiensis israelensis and Brevibacillus laterosporus, was also assessed in field conditions in a comparative study conducted in sheep farm larval development sites, including treatments with the organophosphate temephos. Significant larvicidal properties were associated with the various insecticides evaluated in the laboratory assays and in field trials, although with different levels of effectiveness. While temephos was confirmed to be an effective broad spectrum larvicidal substance, B. laterosporus appeared to be the most effective among entomopathogens, while insect growth regulators combined a good efficacy to a long-lasting residual effect in the field. Everything considered, the use of these biorational insecticides alone or in combination with larval habitat manipulation techniques appears to be a promising method to complement integrated biting midge management programs
Interazioni tra funghi entomopatogeni e nematodi entomopatogeni nel controllo microbiologico
No full textI funghi entomopatogeni (EPF) e i nematodi entomopatogeni (EPN, con i batteri a essi associati) sono
organismi del suolo distribuiti a livello globale in grado di infettare e uccidere una grande varietà di insetti.
Per questa ragione questi organismi sono spesso utilizzati come agenti di controllo microbiologico nella
gestione dei parassiti degli insetti. Sia i funghi entomopatogeni che i nematodi entomopatogeni con i loro
batteri simbionti, condividono l'ambiente “suolo” e quindi possono infestare e competere per lo stesso
insetto ospite, tuttavia raramente si incontrano co-infezioni naturali e le nostre attuali conoscenze sulle loro
interazioni all'interno dell'ospite provengono principalmente da esperimenti di laboratorio. Per una recente
tendenza a combinare agenti di biocontrollo al fine di aumentarne l'efficacia, molti studi si sono concentrati
sulla co-applicazione di diverse specie e/o ceppi di EPF ed EPN contro vari insetti nocivi con esiti variabili che
vanno dall'effetto sinergico, all'effetto additivo o all'antagonismo. Gli effetti sul loro sviluppo variano dalla
normale riproduzione all'esclusione e, in generale, i risultati delle interazioni dipendono dai ceppi di
entomopatogeno, dalla specie ospite, dalle dosi utilizzate e dai tempi d’infezione. Il presente lavoro mira a
riassumere le attuali conoscenze sulle interazioni di EPF e EPN all'interno di un insetto ospite e stimare i
possibili effetti delle interazioni sulle popolazioni di entomopatogeni naturali e sul loro utilizzo nel controllo
microbiologico
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