Nanoencapsulation of biopesticides is an important strategy to increase the efficiency of these compounds, reducing losses and adverse effects on non-target organisms. This study describes the ...preparation and characterisation of zein nanoparticles containing the botanical compounds limonene and carvacrol, responsive to proteolytic enzymes present in the insects guts. The spherical nanoparticles, prepared by the anti-solvent precipitation method, presented in the nanoparticle tracking analysis (NTA) a concentration of 4.7 × 1012 ± 1.3 × 1011 particles.mL−1 and an average size of 125 ± 2 nm. The formulations showed stability over time, in addition to not being phytotoxic to Phaseolus vulgaris plants. In vivo tests demonstrated that formulations of zein nanoparticles containing botanical compounds showed higher mortality to Spodoptera frugiperda larvae. In addition, the FTIC probe (fluorescein isothiocyanate) showed wide distribution in the larvae midgut, as well as being identified in the feces. The trypsin enzyme, as well as the enzymatic extract from insects midgut, was effective in the degradation of nanoparticles containing the mixture of botanical compounds, significantly reducing the concentration of nanoparticles and the changes in size distribution. The zein degradation was confirmed by the disappearance of the protein band in the electrophoresis gel, by the formation of the lower molecular weight fragments and also by the greater release of FTIC after enzymes incubation. In this context, the synthesis of responsive nanoparticles has great potential for application in pest management, increasing the selectivity and specificity of the system and contributing to a more sustainable agriculture.
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•A nanoformulation with the botanical compounds carvacrol and limonene was produced.•The trypsin enzyme and midgut content degraded the zein nanoparticles containing botanical compounds.•Proteolytic action is evidenced by the release of fluorescent probe.•Nanopesticide was effective in control Spodoptera frugiperda.
The nanoencapsulation of botanical compounds (such as geraniol) is an important strategy that can be used to increase the stability and efficiency of these substances in integrated pest management. ...In this study, chitosan/gum arabic nanoparticles containing geraniol were prepared and characterized. In addition, evaluation was made of the biological activity of geraniol encapsulated in chitosan/gum arabic nanoparticles toward whitefly (Bemisia tabaci). The optimized formulation showed a high encapsulation efficiency (>90%) and remained stable for about 120 days. The formulation protected the geraniol against degradation by UV radiation, and the in vitro release was according to a diffusion mechanism that was influenced by temperature. An attraction effect was observed for Bemisia tabaci, indicating the potential of this type of system for use in pest management, especially in trap devices.
Helicoverpa armigera is a polyphagous pest sensitive to Cry1Ac protein from Bacillus thuringiensis (Bt). The susceptibility of the different larval instars of H. armigera to Cry1Ac protoxin showed a ...significant 45-fold reduction in late instars compared to early instars. A possible hypothesis is that gut surface proteins that bind to Cry1Ac differ in both instars, although higher Cry toxin degradation in late instars could also explain the observed differences in susceptibility. Here we compared the Cry1Ac-binding proteins from second and fifth instars by pull-down assays and liquid chromatography coupled to mass spectrometry analysis (LC-MS/MS). The data show differential protein interaction patterns of Cry1Ac in the two instars analyzed. Alkaline phosphatase, and other membrane proteins, such as prohibitin and an anion selective channel protein were identified only in the second instar, suggesting that these proteins may be involved in the higher toxicity of Cry1Ac in early instars of H. armigera. Eleven Cry1Ac binindg proteins were identified exclusively in late instar larvae, like different proteases such as trypsin-like protease, azurocidin-like proteinase, and carboxypeptidase. Different aminopeptidase N isofroms were identified in both instar larvae. We compared the Cry1Ac protoxin degradation using midgut juice from late and early instars, showing that the midgut juice from late instars is more efficient to degrade Cry1Ac protoxin than that of early instars, suggesting that increased proteolytic activity on the toxin could also explain the low Cry1Ac toxicity in late instars.
Bioinsecticides based on
Bacillus thuringiensis
(Bt) Berliner, 1915 are widely used to control lepidopteran in several crops. However, surviving insects exposed to the sub-lethal concentration of ...Bt-based bioinsecticides can suffer a multitude of effects on the biological conditioning known as hormesis. Here, we aimed to provide a clearer understanding of the biological conditioning of
Anticarsia gemmatalis
(Hübner, 1818), exposed to different concentrations of a Bt-based bioinsecticide, by assessing life table parameters over three generations. We defined five sub-lethal concentrations (LC
5
, LC
10
, LC
15
, LC
20
, and LC
25
) from the response curve estimate of
A. gemmatalis
. Deionized water was used as a control. We assessed the parameters of eggs-viability and the duration of the stages, incubation, larval, pre-pupal, pupal, adult, pre-oviposition and total biological cycle. Data were used to construct the fertility life table using the two-sex program. The survival curves showed greater variation in the proportion of individuals at each development stage using the LC
25
. The sub-lethal concentrations did not influence the incubation-eggs period, pre-pupal and pupal. However, the larval and adult stages using LC
25
and LC
10
were the most affected. Changes in sex ratio were observed using LC
20
and LC
5
. The toxic effect of Bt-based bioinsecticide interfered mainly in the parameters of fertility, sex ratio, net reproduction rate (R0), and gross reproduction rate (GRR).
•Bt bioinsecticides have been important in suppressing pest outbreaks in Brazil.•Perspectives discussed for Bt adoption include tank mixture and product formulation.•Possible solutions are presented ...to the main limitations of Bt bioinsecticides.
Biopesticides based on the entomopathogenic bacteria Bacillus thuringiensis (Bt) are used worldwide on broad-extensions of different crops and vegetables, mainly against lepidopteran and coleopteran pests. The first attempts to use this microbial control agent as biopesticide date from 1938, but it was until 1970s that some quality constraints on the formulations were solved, and right now, multiple formulations are available in the market and are used in the field. The high selectivity of Bt pesticidal proteins, without harming natural enemies and non-target organisms, is the main factor involved in their reduced environmental risk, in contrast with the broad-spectrum chemical pesticides. Moreover, the high efficacy of Bt biopesticides has already played a significant role in suppressing some pests' outbreaks. Nevertheless, despite the improvements of Bt formulations over the past 50 years, abiotic factors such as temperature, ultraviolet radiation, rainfall, and other factors such as farmer practices are still considered the main obstacles to the broader adoption of Bt biopesticides. Here, we discuss the challenges of Bt biopesticides and the perspectives to improve their adoption, including tank mixtures, technology application, formulations, and insect resistance.
Nanomaterials composed of natural matrices associated with biopesticides have promising applications in sustainable agriculture. In this study, the biopesticide neem oil was encapsulated in zein ...nanoparticles in order to improve its stability and efficiency. Assays of phytotoxicity (using
Phaseolus vulgaris
) and biological activity against three pests (
Acanthoscelides obtectus
,
Bemisia tabaci
, and
Tetranychus urticae
) were also performed. The neem oil-loaded zein nanoparticles presented 198 ± 16 nm, polydispersity index of around 0.2, satisfactory physicochemical stability, together with high encapsulation efficiency (> 80%). Pre- and postemergence treatments using this new system did not cause any phytotoxic effects toward
P. vulgaris
. The neem oil nanobiopesticide exhibited mortality effects on
B. tabaci
and
T. urticae
, while the effect against
A. obtectus
was significantly increased, compared to plain neem oil. The results of the characterization, toxicity, and biological activity studies showed the promising potential of these neem oil-loaded zein nanoparticles for the use in pest management in sustainable agriculture after the required toxicological assessments.
Spodoptera frugiperda is a pest of economic importance for several crops with resistance reports to Bt crops and pesticides. Eco-friendly Bt biopesticides may be an alternative to chemical ...insecticides due to their selectivity and specificity. However, the efficacy of Bt biopesticides may be influenced by the association with other chemicals, such as adjuvants. This study evaluated the compatibility and toxicity of Bt biopesticides mixed with adjuvants for the control of S. frugiperda. The treatments included the association of Dipel SC and Dipel PM with adjuvants. Compatibility tests were used to evaluate the Bt mixture. Bt suspensions obtained from mixtures of Bt and adjuvants at 10
and 3 × 10
spores/mL
were used to evaluate S. frugiperda mortality and distilled water was used as the control. The addition of the adjuvant LI increased growth and sporulation, indicating compatibility with Bt biopesticides. The other adjuvants were toxic to reducing Bt growth and sporulation. Only the mixture of Bt with LI and Bt alone was effective to S. frugiperda. The addition of adjuvants to Bt biopesticide affect the Bt sporulation, growth and mortality.
Abstract
Bacillus thuringiensis
(Bt) isolates native to Maranhão (BtMA) that are highly toxic to
Aedes aegypti
larvae and seven standard subspecies of Bt were analyzed for genetic diversity using the ...rep-PRC technique with BOX, ERIC, REP, MB1, and GTG
5
markers. The rep-PCR technique is considered an extremely reliable, reproducible, fast and highly discriminatory technique that may be used even among populations of the same species. These five markers revealed a total of 38 polymorphic DNA fragments for 30 BtMA isolates. Eight groups were obtained with the dendrogram generated through Pearson's correlation analysis, with four groups formed only with BtMA isolates and four comprised of isolates of BtMA and the standard subspecies toxic to dipterans and lepidopterans. Despite the high genetic diversity of BtMA, a low correlation between the collection site, gene content and mortality against
A. aegypti
larvae was evidenced. The clustering of the standard subspecies of Bt that were toxic against dipterans with BtMA isolates confirm the mosquitocidal action of the native isolates from Maranhão, and they can be used as an alternative for
A. aegypti
control and other insects of medical importance and for the control of agricultural pests.
is a major insect pest of several crops worldwide. This insect is susceptible to some
(Bt) Cry insecticidal proteins expressed in transgenic crops or used in biopesticides. Previously, we identified
...prohibitin (HaPHB) as a Cry1Ac-binding protein. Here, we further analyzed the potential role of PHB as a Cry toxin receptor in comparison to cadherin (CAD), well recognized as a Cry1Ac receptor. HaPHB-2 midgut protein and HaCAD toxin-binding region (TBR) fragment from
were expressed in
cells, and binding assays with different Cry1 toxins were performed. We demonstrated that Cry1Ab, Cry1Ac, and Cry1Fa toxins bound to HaPHB-2 in a manner similar to that seen with HaCAD-TBR. Different Cry1Ab mutant toxins located in domain II (Cry1AbF371A and Cry1AbG439D) or domain III (Cry1AbL511A and Cry1AbN514A), which were previously characterized and found to be affected in receptor binding, were analyzed regarding their binding interaction with HaPHB-2 and toxicity against
One β-16 mutant (Cry1AbN514A) showed increased binding to HaPHB-2 that correlated with 6-fold-higher toxicity against
, whereas the other β-16 mutant (Cry1AbL511A) was affected in binding to HaPHB-2 and lost toxicity against
Our data indicate that β-16 from domain III of Cry1Ab is involved in interactions with HaPHB-2 and in toxicity. This report identifies a region of Cry1Ab involved in binding to HaPHB-2 from a Lepidoptera insect, suggesting that this protein may participate as a novel receptor in the mechanism of action of the Cry1 toxins in
is a polyphagous pest that feeds on important crops worldwide. This insect pest is sensitive to different Cry1 toxins from
In this study, we analyzed the potential role of PHB-2 as a Cry1 toxin receptor in comparison to CAD. We show that different Cry1 toxins bound to HaPHB-2 and HaCAD-TBR similarly and identify β-16 from domain III of Cry1Ab as a binding region involved in the interaction with HaPHB-2 and in toxicity. This report characterized HaPHB-Cry1 binding interaction, providing novel insights into potential target sites for improving Cry1 toxicity against
.
Bacillus thuringiensis (Bt) is the main bacterium used in the formulation of bioinsecticides because it produces toxins and spores that are toxic to several orders of insects. The efficacy of Bt ...bioinsecticide is influenced by the quality of its application. The association with other crop protection products, such as adjuvants, can affect the physical and chemical parameters of the mixture. This study evaluated the physical and chemical parameters, volume median diameter (VMD), uniformity coefficient of droplets (SPAN), percentage of volume in drift droplets (%V <100 µm), contact angle, surface tension, potential of hydrogen (pH) and electrical conductivity (E.C.) of Bt bioinsecticides in concentrated suspension (SC), and wettable powder (WP) formulations associated with adjuvants. The largest droplet diameter and smallest values of drift droplets were found in the WP formulation with lower drift potential. The addition of mineral oil and surfactant to the mixtures of bioinsecticide reduced contact angle values and surface tension of the droplets, resulting in greater spreading of droplets in leaves. The addition of lecithin and propionic-acid-based adjuvants lowered the pH in both formulations. The adjuvants used in this study affected the physical and chemical characteristics of the mixtures, improving or impairing the quality of Bt bioinsecticide applications.
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