Exploring the chemical characterization and insecticidal activities of Curcuma angustifolia roxb. leaf essential oils against three major stored product insects

Botanical pesticides are safe and widely used in pest management. Curcuma angustifolia belongs to the family Zingiberaceae and is a rhizomatous medicinal herb. Following rhizome harvesting, leaves are discarded as waste. However, they can be effectively utilized by extracting essential oils, which are potential biopesticides. The aim of the study is to evaluate the efficacy of the leaf essential oil of Curcuma angustifolia as a potential biopesticide against three stored grain pests, Lasioderma serricorne, Tribolium castaneum, and Callasobruchus chinensis, by their contact, fumigant, and repellent activities. The leaves yield 0.39 ± 0.02 % of oil by hydrodistillation. GC-MS/MS characterization identified curzerenone (18.37 %), geranyl-p-cymene (17.32 %), α-elemenone (13.59 %), eucalyptol (7.58 %) as the main constituents. When exposed to different concentrations of C. angustifolia oil, the test insect displayed noticeably high repellency rates. It also showed better contact toxicity at 24 h, LC50 = 0.22 mg/cm2 for cigarette beetle, LC50 = 0.64 mg/cm2 for red flour beetle, LC50 = 0.07 mg/cm2 for pulse beetle) and fumigation toxicities (LC50 = 10.8 mg/L air at 24 h, for cigarette, LC50 = 29.5 mg/L air for red flour beetle, LC50 = 7.9 mg/L air for pulse beetle). Additionally, a phytotoxicity study was done on paddy seeds, and the results showed no effect on seed germination or seedling growth. It was evident from this study that C. angustifolia oil from waste leaves can be utilized as a botanical pesticide to manage the adults of these storage pests.

N-terminal proteolysis determines the differential activity of Bacillus thuringiensis Cry2A toxins towards Aedes aegypti

It has long been known that while both the Bacillus thuringiensis pesticidal proteins Cry2Aa and Cry2Ab have wide-ranging activities against lepidopteran insects only the former has activity against the mosquito Aedes aegypti. We have previously shown that this differential specificity is influenced by the N-terminal region of these proteins and here demonstrate that this is due to these sections affecting proteolytic activation. Enzymes from the midgut of A. aegypti cleave Cry2Aa at the C-terminal side of amino acid 49 resulting in a 58 kDa fragment whereas these enzymes do not cleave Cry2Ab at this position. The 58 kDa, but not the protoxin, form of Cry2Aa is capable of interacting with brush border membrane vesicles from A. aegypti.

Biosynthetic pathway redesign in non-conventional yeast for enhanced production of cembratriene-ol

Cembratriene-ol (CBT-ol), a plant-derived macrocyclic diterpene with notable insecticidal activity, has attracted considerable attention with respect to the development of sustainable and green biopesticides. Currently, CBT-ol production is limited by an inefficient and costly plant extraction strategy. Herein, CBT-ol production was enhanced by redesigning the CBT-ol biosynthetic pathway in Candida tropicalis, with subsequent truncation of CBT-ol synthase further increasing CBT-ol production. Moreover, bottlenecks in the CBT-ol biosynthetic pathway were eliminated by adjusting the gene dosage of the rate-limiting enzymes. Ultimately, the resulting strain C. tropicalis CPPt-03D produced 129.17 mg/L CBT-ol in shaking flasks (a 144-fold increase relative to that of the initial strain C01-CD) with CBT-ol production reaching 1,425.76 mg/L in a 5-L bioreactor, representing the highest CBT-ol titer reported to date. These findings provide a green process and promising platform for the industrial production of CBT-ol and lays the foundation for organic farming.

Microsclerotia from Metarhizium robertsii: Production, ultrastructural analysis, robustness, and insecticidal activity

Microsclerotia (MS) are considered one of the most promising propagules for use as active ingredients in biopesticides due to their tolerance to abiotic factors and ability to produce infective conidia for the control of pests. Therefore, the objective of this research was to establish the conditions required to induce the formation of microsclerotia in Metarhizium robertsii Mt004 and to study its development process, tolerance to abiotic factors and insecticidal activity of MS-derived conidia. M. robertsii started to form hyphal aggregates after 2 days and looked more compact after 8 days. MS were mature and pigmented after 20 days. The final yield was 2.0 × 103 MS/mL and MS size varied between 356.9 and 1348.4 μm. Ultrastructure analysis revealed that mature MS contained only a few live cells embedded in an extracellular matrix. Mature MS were more tolerance to UV-B radiation, heat and storage trials than conidia from Solid State Fermentation. MS-derived conidia were as virulent as conidia against Diatraea saccharalis larvae. These results showed that MS are promising propagules for the development of more persistent and efficient biopesticides for harsh environmental conditions. Our findings provide a baseline for production and a better understanding of microsclerotia development in M. robertsii strains.

Antagonistic and additive effect when combining biopesticides against the fall armyworm, Spodoptera frugiperda

Fall armyworm, Spodoptera frugiperda (FAW) is a cosmopolitan crop pest species that has recently become established in sub-Saharan Africa and Southeast Asia. Current FAW control is almost entirely dependent on synthetic pesticides. Biopesticides offer a more sustainable alternative but have limitations. For example, pyrethrum is an effective botanical insecticide with low mammalian toxicity but is highly UV labile, resulting in a rapid loss of efficacy in the field. Beauveria bassiana is an entomopathogenic fungus that is more persistent, but there is a time lag of several days before it causes insect mortality and leads to effective control. The combination of these biopesticides could mitigate their drawbacks for FAW control. Here we evaluated the efficacy of pyrethrum and B. bassiana as individual treatments and in combination against 3rd instar FAW. Four different combinations of these two biopesticides were tested, resulting in an antagonistic relationship at the lowest concentrations of B. bassiana and pyrethrum (1 × 104 conidia mL-1 with 25 ppm) and an additive effect for the other 3 combined treatments (1 × 104 conidia mL-1 with 100 ppm and 1 × 105 conidia mL-1 with 25 ppm and 100 ppm pyrethrum). Additionally, a delay in efficacy from B. bassiana was observed when combined with pyrethrum as well as a general inhibition of growth on agar plates. These results appear to show that this particular combination of biopesticides is not universally beneficial or detrimental to pest control strategies and is dependent on the doses of each biopesticide applied. However, the additive effect shown here at specific concentrations does indicate that combining biopesticides could help overcome the challenges of persistence seen in botanical pesticides and the slow establishment of EPF, with the potential to improve effectiveness of biopesticides for IPM.

Biopesticide Turex®'s cytotoxicity, genotoxicity and cell cycle arrest on HepG2 cell line

Population growth leads to the need for more efficient techniques and compounds in agriculture, such as pesticides, to deal with the ever-growing demand. Pesticides may end up in the environment, often compromising the ecosystem affecting all organisms including humans. Therefore, the consequences of exposure to these compounds to biota and humans needs to be assessed. Bearing this in mind, the aim of this study was to examine the in vitro cytotoxicity and genotoxicity attributed to exposure to the biopesticide Turex® utilizing the liver cell line HepG2. Cells were incubated with biopesticide Turex® at 250, 500, 1000, 1500 or 2000 μg/L in both non-activated and activated forms for 24 and 48 h. Subsequent effects on cell viability were assessed using the MTT. The influence on cell cycle dynamics was determined by flow cytometry, while DNA damage was measured by the comet assay. Data demonstrated that activated Turex® induced cytotoxicity and DNA damage after 48 h in HepG2 cell line. The cell cycle progression was not markedly affected by Turex® at any concentration or duration of exposure. In conclusion, data demonstrated the potential adverse effects attributed to exposure to biopesticide Turex® in human cell line HepG2. Consequently, this type of biopesticide needs to be further investigated to determine the potential adverse in vivo effects on various non-target organisms.

In vitro Genotoxicity and In silico Docking Analyses of the Essential Oils of Thuja orientalis

Two main objectives were pursued to assess the reliability of Thuja orientalis essential oils (TOEO). The first objective was to extract TOEO, analyze them by GC-MS, and determine their in vitro genotoxicity against selected plants using the RAPD-PCR method. The second objective was to evaluate the in-silico toxicity of TOEO. The binding sites and energies of each content was calculated against B-DNA. In-silico analyses were performed using a simulation program, AutoDock Vina, and Toxicity Estimation Software Tools. 3-carene, cedrol, and 2-pinene were identified as the predominant components. In vitro studies showed that the TOEO had a more significant impact on reducing genomic stability in wheat compared to the amaranth. The lowest stability was determined as 39.78 % in wheat and 53.58 % in amaranth. Cedrol (-5,7 kcal/mol) and selinene (-5,6 kcal/mol) exhibited the highest binding affinity. The toxicity test indicated that components other than cyclohexene may have toxic effects, none of them were predicted to be mutagenic, and LD50 (mol/kg) values could vary between 1.33 and 1.55.

Diverse roles played by "Pseudomonas fluorescens complex" volatile compounds in their interaction with phytopathogenic microrganims, pests and plants

Pseudomonas fluorescens complex consists of environmental and some human opportunistic pathogenic bacteria. It includes mainly beneficial and few phytopathogenic species that are common inhabitants of soil and plant rhizosphere. Many members of the group are in fact known as effective biocontrol agents of plant pathogens and as plant growth promoters and for these attitudes they are of great interest for biotechnological applications. The antagonistic activity of fluorescent Pseudomonas is mainly related to the production of several antibiotic compounds, lytic enzymes, lipopeptides and siderophores. Several volatile organic compounds are also synthesized by fluorescent Pseudomonas including different kinds of molecules that are involved in antagonistic interactions with other organisms and in the induction of systemic responses in plants. This review will mainly focus on the volatile compounds emitted by some members of P. fluorescens complex so far identified, with the aim to highlight the role played by these molecules in the interaction of the bacteria with phytopathogenic micro and macro-organisms and plants.

Improved Expression of a Thermostable GH18 Bacterial Chitinase in Two Different Escherichia coli Strains and Its Potential Use in Plant Protection and Biocontrol of Phytopathogenic Fungi

Chitinases are enzymes that can break down chitin, a major component of the exoskeleton of insects and fungi. This feature makes them potential biopesticides in agriculture since they are considered a safe and environmentally friendly alternative to synthetic pesticides. In this work, we performed a comparative study between two different bacterial expression strains to produce a recombinant chitinase with improved stability. Escherichia coli strains Origami B and BL21 (DE3) were selected for their distinct cytosolic environment to express BhChitA chitinase of Bacillus halodurans C-125 and to investigate the role of disulfide bond formation and proper folding on its stability and activity. Expression of the recombinant BhChitA in bacterial strain containing oxidative cytosol (Origami B) improved its activity and stability. Although both expression systems have comparable biochemical properties (temperature range 20-80 °C and pH spectrum 3-10), BhChitA expressed in Origami strain seems more stable than expressed in BL21. Furthermore, the optimal expression conditions of the recombinant BhChitA has been carried out at 30 °C during 6 h for the Origami strain, against 20 °C during 2 h for BL21. On the other hand, no significant differences were detected between the two enzymes when the effect of metal ions was tested. These findings correlate with the analysis of the overall structure of BhChitA. The model structure permitted to localize disulfide bond, which form a stable connection between the substrate-binding residues and the hydrophobic core. This link is required for efficient binding of the chitin insertion domain to the substrate. BhChitA exhibited in vitro antifungal effect against phytopathogenic fungi and suppressed necrosis of Botrytis cinerea on detached tomato leaves. In vitro assays showed the influence of BhChitA on growth suppression of Botrytis cinerea (53%) Aspergillus niger (65%), Fusarium graminearum (25%), and Fusarium oxysporum (34%). Our results highlight the importance of the bacterial expression system with oxidative cytosol in producing promising biopesticides that can be applied for post-harvest processing and crop protection.

Aiming for a Better Tomorrow

How to cite this article: Kharbanda M. Aiming for a Better Tomorrow. Indian J Crit Care Med 2024;28(1):11-12.

Valorization of Chlorella thermophila biomass cultivated in dairy wastewater for biopesticide production against bacterial rice blight: a circular biorefinery approach

Biopesticides offer a sustainable and efficient alternative to synthetic pesticides, providing a safer and more eco-friendly solution to pest management. The present work proposes an innovative approach that integrates crop protection and wastewater treatment using thermophilic microalgal strain Chlorella thermophila (CT) cultivated in nutrient-rich dairy wastewater as a growth medium. The microalgae was cultivated mixotrophically and was able to reduce both organic carbon as well as nutrient load of the dairy wastewater efficiently. The integrated circular biorefinery approach combines biomass cultivation, extraction of biopesticide compounds, and conversion to biocrude. The antimicrobial activity of the biopesticidal extracts against Xanthomonas oryzae and Pantoea agglomerans, the causative agent of bacterial rice blight, is assessed through in vitro studies. The biomass extract obtained is able to inhibit the growth of both the above-mentioned plant pathogens successfully. Mass spectroscopy analysis indicates the presence of Neophytadiene that has previously been reported for the inhibition of several pathogenic bacteria and fungi. Several other value-added products such as linoleic acid and nervonic acids were also been detected in the microalgal biomass which have extremely high nutraceutical and medicinal values. Furthermore, the study investigates the potential for co-production of biocrude from the biorefinery process via hydrothermal liquefaction. Overall, the findings of this present work represent an innovative and sustainable approach that combines wastewater treatment and crop protection using microalgal biomass.

Eco-friendly biopesticides derived from CO2-Fixing cyanobacteria

There is currently an escalating global demand for the utilization of plant and natural extracts as pesticides due to their minimal health risks. Cyanobacteria are highly valuable organisms with significant potential in agriculture and are of great interest for the development of agrochemical agents as biopesticides. The flexibility and adaptability of Cyanobacteria to various environmental conditions are facilitated by the presence of specialized enzymes involved in the production of biologically active diverse secondary metabolites, including alkaloids, lipopolysaccharides, non-protein amino acids, non-ribosomal peptides, polyketides, terpenoids, and others. This review focuses on the metabolites synthesized from cyanobacteria that have demonstrated effectiveness as antibacterial, antiviral, antifungal agents, insecticides, herbicides, and more. The potential role of cyanobacteria as an alternative to chemical pesticides for environmental conservation is discussed.

Toxicity assessment of a novel biopesticide guvermectin and identification of its transformation products in soils

Guvermectin is a novel biopesticide often used as seed soaking to promote the rice yield. However, its biotoxicity and degradation behavior in soils were still not disclosed, which posed a knowledge gap to guide its rational application. Therefore, the degradation behaviors of guvermectin in four typical soils under aerobic and anaerobic conditions were investigated in the laboratory. The results showed that guvermectin was degraded fast with DT50 ranging from 0.95 to 10.10 d, and the degradation rate was higher in aerobic condition than that in anaerobic condition. Eight transformation products were screened using UPLC-QTOF/MS. The acute toxicities tests of guvermectin to Coturnix coturnix japonica and Apis mellifera were measured by biological laboratory experiments, and the acute and chronic toxicities of transformation products to Danio rerio, Daphnia magna Straus and Green algae were predicted by ECOSAR software. The results showed that guvermectin has low toxic to quail and honeybee (LD50 2000 mg a.i./kg body weight, LD50 ˃ 100 μg a.i./bee), and its transformation products were also low toxic class to Danio rerio, Daphnia magna Straus and Green algae (LC50/EC50 > 100 mg a.i./L). However, the nucleoside-like metabolites may pose a potential risk due to their similarity to genetic material, which should be concerned. The findings provided important environmental risk assessment data for the rational use of guvermectin.

Immunomodulatory, cyto-genotoxic, and growth regulatory effects of nerolidol on melon fruit fly, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae)

Insects have evolved a robust immune system consisting of humoral and cellular branches and their orchestrated response enables insect to defend against exogenous stressors. Exploration of underlying immune mechanisms of insect pest under allelochemical stress can give us new insights on insect pest management. In this study, nerolidol, a plant sesquiterpene was evaluated for its insecticidal, growth regulatory, immunomodulatory, and cyto-genotoxic effects against melon fruit fly, Zeugodacus cucurbitae (Coquillett). First, second, and third instar larvae of Z. cucurbitae were fed on artificial diet containing different concentrations (5, 25, 125, 625, and 3125 ppm) of nerolidol. Results revealed a significant reduction in pupation and adult emergence as well as prolongation of developmental duration of treated larvae. Decline in growth indices showed remarkable growth inhibitory effects of nerolidol. Pupal weight and nutritional parameters viz. Larval weight gain, food assimilated, and mean relative growth rate declined after treatment. Immunological studies on second instar larvae depicted a drop in total hemocyte count and variations in proportions of plasmatocytes and granulocytes of LC30 and LC50 treated larvae. Phenoloxidase activity in nerolidol treated larvae initially increased but was suppressed after 72 h of treatment. The frequency of viable hemocytes decreased and that of apoptotic and necrotic hemocytes increased with both the lethal concentrations of nerolidol. Comet assay revealed a significant damage to DNA of hemocytes. The findings of the current study indicate that nerolidol exerts its insecticidal action through growth regulation, immunomodulation, and cyto-genotoxicity thus revealing its potential to be used as biopesticide against Z. cucurbitae.

RNAi-based silencing of proteasome 20S subunit alpha 2 affected the survival and development of Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is a notorious pest of solanaceous plants in Asia, which is mainly managed by chemical pesticides. RNA interference (RNAi) technique is considered to be a promising and effective alternative for pest control. In this study, we selected the proteasome 20S subunit alpha 2 (Prosα2) gene, a cellular protein involved in many proteins regulatory processes, to explore the RNAi efficiency in H. vigintioctopunctata. The obtained results confirmed the significant lethal effects of HvProsα2 silencing on the H. vigintioctopunctata 1st instar larvae at concentrations of 100, 50, and 5 ng/μL. Ingestion of the bacterially expressed dsHvProsα2 caused high mortality in both larvae and adults. Moreover, silencing of HvProsα2 resulted in feeding disorders, growth delay, and abnormal intestinal development of the larvae. Overall, HvProsα2 acts as an important regulator for the growth and development of H. vigintioctopunctata, and can serve as a candidate target gene for the RNAi-based control of H. vigintioctopunctata.

Trichoderma as a biological control agent: mechanisms of action, benefits for crops and development of formulations

Currently, the food and economic losses generated by the attack of phytopathogens on the agricultural sector constitute a severe problem. Conventional crop protection techniques based on the application of synthetic pesticides to combat these undesirable microorganisms have also begun to represent an inconvenience since the excessive use of these substances is associated with contamination problems and severe damage to the health of farmers, consumers, and communities surrounding the fields, as well as the generation of resistance by the phytopathogens to be combated. Using biocontrol agents such as Trichoderma to mitigate the attack of phytopathogens represents an alternative to synthetic pesticides, safe for health and the environment. This work explains the mechanisms of action through which Trichoderma exerts biological control, some of the beneficial aspects that it confers to the development of crops through its symbiotic interaction with plants, and the bioremedial effects that it presents in fields contaminated by synthetic pesticides. Also, detail the production of spore-based biopesticides through fermentation processes and formulation development.

Biologically synthesized zinc and copper oxide nanoparticles using Cannabis sativa L. enhance soybean (Glycine max) defense against fusarium virguliforme

In this study, zinc and copper oxide nanoparticles (NPs) were synthesized using hemp (Cannabis sativa L.) leaves (ZnONP-HL and CuONP-HL), and their antifungal potential was assessed against Fusarium virguliforme in soybean (Glycine max L.). Hemp was selected because it is known to contain large quantities of secondary metabolites that can potentially enhance the reactivity of NPs through surface property modification. Synthesizing NPs with biologically derived materials allows to avoid the use of harsh and expensive synthetic reducing and capping agents. The ZnONP-HL and CuONP-HL showed average grain/crystallite size of 13.51 nm and 7.36 nm, respectively. The biologically synthesized NPs compared well with their chemically synthesized counterparts (ZnONP chem, and CuONP chem; 18.75 nm and 10.05 nm, respectively), confirming the stabilizing role of hemp-derived biomolecules. Analysis of the hemp leaf extract and functional groups that were associated with ZnONP-HL and CuONP-HL confirmed the presence of terpenes, flavonoids, and phenolic compounds. Biosynthesized NPs were applied on soybeans as bio-nano-fungicides against F. virguliforme via foliar treatments. ZnONP-HL and CuONP-HL at 200 μg/mL significantly (p < 0.05) increased (∼ 50%) soybean growth, compared to diseased controls. The NPs improved the nutrient (e.g., K, Ca, P) content and enhanced photosynthetic indicators of the plants by 100-200%. A 300% increase in the expression of soybean pathogenesis related GmPR genes encoding antifungal and defense proteins confirmed that the biosynthesized NPs enhanced disease resistance against the fungal phytopathogen. The findings from this study provide novel evidence of systemic suppression of fungal disease by nanobiopesticides, via promoting plant defense mechanisms.

Bacillus thuringiensis pesticidal toxins: A global analysis based on a scientometric study (1980-2021)

Several studies have been conducted on Bacillus thuringiensis (Bt) pesticidal toxins due to their successful environmentally friendly biopesticide activity against various insect pest orders, protozoa, mites, and nematodes. However, no existing study has systematically examined the trends and evolution of research on Bt pesticidal toxins from a scientometric perspective. This study aimed to analyze the trends and hotspots of global research in this field. 5757 publications on Bt pesticidal toxins were extracted from the Web of Science Core Collection (WoS) from 1980 to 2021. Statistical and scientometric analyses were performed using Excel, CiteSpace, and VOSviewer visualization tools to evaluate research evolution, journal contribution and subject categories, contributing countries and institutions, highly influential references, and most used author keywords. The 5757 publications featured in 917 journals spanning 116 subject categories. The top 5 subject categories ranked as Entomology, Biotechnology & Applied Microbiology, Microbiology, Biochemistry & Molecular Biology, and Agriculture. Out of these publications, the USA contributed the most, with 1562 publications, 72,754 citations, and 46.58 average citations per paper (ACPP); however, Belgium had the highest (106.43) ACPP among the top 20 contributing countries. The Chinese Academy of Agricultural Sciences is the leading institution with 298 publications and 21.20 ACPP. The Pasteur Institute is ranked first (90.04) in terms of ACPP. Keywords analyses revealed that recent studies are inclined toward the evolution of insect resistance against Bt toxins. In future, studies related to the development of resistance mechanisms by insects against Bt pesticidal toxins and ways to overcome them will likely receive more attention. This study highlights the past and current situations and prospective directions of Bt pesticidal toxins-related research.

Solid-state fermentation in an earthen vessel: Trichoderma viride spore-based biopesticide production using corn cobs

The present study reports the production of Trichoderma viride spores in an earthen vessel using corn cobs. Using 4 kg of corn cobs, spore-based biopesticide was produced after 21 d with a maximum spore count of 2.50 × 109 spores/g of substrate and a moisture reduction from 70.80% w/v to 8.10% w/v. The gas chromatography-mass spectrometry analysis of its ethyl acetate extract revealed that it had 20 secondary metabolites, of which 13 were known to be antimicrobial, one was plant growth-promoting, and one performed both functions. Dried extract dissolved in methanol showed the minimum fungicidal concentration of 5-10 mg/ml against Rhizoctonia solani on potato dextrose agar plate. Plate assays and pot experiments on Rhizoctonia solani-infected potato plants exhibited good antifungal and plant growth-promoting activities. The biopesticide showed 71.28% viability over 10 m of storage in the same earthen vessel at 30 ± 2 °C. Thus, a simple, robust technology was developed with good potential for farm deployment.

Aging, land fragmentation, and banana farmers' adoption of biopesticides in China

Encouraging farmers to adopt biopesticides is a crucial strategy for protecting the ecological environment and achieving sustainable agricultural development. This study utilizes data from a micro-survey of 454 banana farmers from Hainan Province of China and employs a logit model to analyze the effects of aging, land fragmentation, and their interactions on farmers' adoption of biopesticides, as well as the heterogeneity of farmers in different household life cycles. The findings reveal that aging and land fragmentation both hinder biopesticide adoption, with farmers experiencing higher levels of aging and more fragmented land holdings being less likely to utilize biopesticides in banana production. Mechanism analysis uncovers an interaction effect between aging and land fragmentation that hampers biopesticide adoption. Furthermore, the effects of aging, land fragmentation, and their interaction on biopesticide adoption behavior vary across farmers in different family life cycles. Specifically, aging negatively affects biopesticide adoption behavior for farmers in support households, while land fragmentation negatively influences farmers in dependency and burden households. The interaction between aging and land fragmentation adversely affects farmers in burden households. Our findings highlight the importance of aging agricultural labor and land fragmentation to promote green agriculture in China and call for more relevant policies to encourage farmers with different household life cycles to adopt biopesticides in farming practices.

Agricultural products from algal biomass grown in piggery wastewater: A techno-economic analysis

The intensification of livestock activities lead to an increase in waste generation with high content of nutrients, as is the case of piggery wastewater. However, this type of residue can be used as culture media for algae cultivation in thin-layer cascade photobioreactors to reduce its environment impact and produce a valorizable algal biomass. Biostimulants were produced by enzymatic hydrolysis and ultrasonication of microalgal biomass, using membranes (Scenario 1) or centrifugation (Scenario 2) as harvesting methods. The co-production of biopesticides by solvent extraction was also evaluated using membranes (Scenario 3) or centrifugation (Scenario 4). The four scenarios were analyzed by a technoeconomic assessment estimating the total annualized equivalent cost and the production cost, i.e., the minimum selling price. Centrifugation provided biostimulants approximately 4 times more concentrated than membranes, but with higher expense due to the cost of the centrifuge (contribution of 62.2 % in scenario 2) and the electricity requirements. The biopesticide production resulted the highest contribution to investment cost in scenarios 3 and 4 (34 % and 43 % respectively). The use of membranes was also more advantageous to produce biopesticides, although it was 5 times more diluted than using centrifuge. The biostimulant production cost was 65.5 €/m³ with membranes and 342.6 €/m³ by centrifugation and the biopesticide production cost was 353.7 €/m³ in scenario 3 and 2122.1 €/m³ in scenario 4. Comparing the treatment of 1 ha of land, the cost of the biostimulant produced in the four scenarios was lower than the commercial one (48.1 %, 22.1 %, 45.1 % and 24.2 % respectively). Finally, using membranes for biomass harvesting allowed economically viable plants with lower capacity and longer distance for biostimulant distribution (up to 300 km) than centrifuge (188 km). The algal biomass valorization for agricultural products production is an environmentally and economically feasible process with the adequate capacity of the plant and distribution distance.

Lutein Production by Halophilic Microalgae Using Anaerobic Digestate as the Substrate and Its Potential Application as a Biopesticide

Production of value-added products from waste anaerobic digestate is economically and environmentally important for sustainable development of industrial process and products. In this study halophilic microalgae, Chlorella vulgaris 92001, Chlorella vulgaris 50291, Chlorella vulgaris 10241 and Tetraselmis indica, were initially screened for lutein production using synthetic dairy digestate (DD), municipal digestate (MD) and poultry digestate (PD) as no-cost substrates. Screening and optimization of parameters, such as dilution, pH, MgCl₂, NaCl, NaHCO₃ and inoculum concentration for maximum lutein production were further performed employing statistically designed Plackett-Burman and response surface methodology. Cultivation of C. vulgaris 92001 in a split column photobioreactor under optimum culture condition showed increase in lutein production by 2.36-fold in batch mode. The influence of different hydraulic retention time (HRT) values of 150, 130, 100 and 90 h on lutein production was evaluated in continuous mode with the split column photobioreactor. Lutein produced using the synthetic poultry digestate showed good potential biopesticide activity against Spodoptera litura (fall armyworm). Overall, this study demonstrated bioprocess development to produce lutein using synthetic anaerobic digestate from marine algae and its potential application as a biopesticide.

Filling in the gaps in biowaste biorefineries: The use of the solid residue after enzymatic hydrolysis for the production of biopesticides through solid-state fermentation

Alternative production processes using waste are necessary to preserve non-renewable resources and prevent scarcity of materials for future generations. Biowaste, the organic fraction of municipal solid waste, is abundant and easily available. It can be fractionated into building blocks for which fermentative processes can be designed. By using solid-state fermentation, this paper proposes a method of valorizing biowaste's residual solid fraction after enzymatic hydrolysis. In a 22 L bioreactor, two digestates from anaerobic digestion processes were evaluated as cosubstrates to modify the acidic pH of the solid residue after enzymatic hydrolysis and promote the growth of the bacterial biopesticide producer Bacillus thuringiensis. Regardless of the cosubstrate used, the final microbial populations were similar indicating microbial specialization. The final product contained 4 × 10⁸ spores per gram of dry matter and also crystal proteins of Bacillus thuringiensis var israelensis, which have insecticidal activity against pests. This method allows for the sustainable use of all materials liberated during the enzymatic hydrolysis of biowaste, including residual solids.

KMC4 grown in simulated dairy wastewater

The present work aims on developing an eco-friendly strategy that couples the remediation of dairy wastewater with crop protection strategy using microalgal biomass for sustainable agriculture. In the present study, the microalgal strain Monoraphidium sp. KMC4 was cultivated in dairy wastewater. It was observed that the microalgal strain is able to tolerate up to as high as 2000 mg/L of COD and utilize the organic carbon and other nutrient component of the wastewater for biomass production. The biomass extract demonstrates excellent antimicrobial activity against the two phytopathogens (Xanthomonas oryzae and Pantoea agglomerans). GC-MS analysis of the microalgae extract revealed phytochemicals such as chloroacetic acid and 2, 4- di tert butylphenol that are responsible for the inhibition of the microbial growth. These preliminary results indicates that integration of microalgal cultivation and nutrient recycling from wastewaters for the production of biopesticides is a promising prospect for the replacement of synthetic pesticides.

Bacterial volatile organic compounds as biopesticides, growth promoters and plant-defense elicitors: Current understanding and future scope

Bacteria emit a large number of volatile organic compounds (VOCs) into the environment. VOCs are species-specific and their emission depends on environmental conditions, such as growth medium, pH, temperature, incubation time and interaction with other microorganisms. These VOCs can enhance plant growth, suppress pathogens and act as signaling molecules during plant-microorganism interactions. Some bacterial VOCs have been reported to show strong antimicrobial, nematicidal, pesticidal, plant defense, induced tolerance and plant-growth-promoting activities under controlled conditions. Commonly produced antifungal VOCs include dimethyl trisulfide, dimethyl disulfide, benzothiazole, nonane, decanone and 1-butanol. Species of Bacillus, Pseudomonas, Arthrobacter, Enterobacter and Burkholderia produce plant growth promoting VOCs, such as acetoin and 2,3-butenediol. These VOCs affect expression of genes involved in defense and development in plant species (i.e., Arabidopsis, tobacco, tomato, potato, millet and maize). VOCs are also implicated in altering pathogenesis-related genes, inducing systemic resistance, modulating plant metabolic pathways and acquiring nutrients. However, detailed mechanisms of action of VOCs need to be further explored. This review summarizes the bioactive VOCs produced by diverse bacterial species as an alternative to agrochemicals, their mechanism of action and challenges for employment of bacterial VOCs for sustainable agricultural practices. Future studies on technological improvements for bacterial VOCs application under greenhouse and open field conditions are warranted.

Pyroligneous acids from biomass charcoal by-product as a potential non-selective bioherbicide for organic farming: its chemical components, greenhouse phytotoxicity and field efficacy

Effective and environmentally friendly herbicides are urgently needed to meet consumer demand for organic products. To evaluate the weed control effect of four pyroligneous acid (PAs) mixtures, the byproducts of bamboo/wood/straw vinegar, two herbicide discovery tests were done: (1) the greenhouse tests by using four indicative plants: wheat (Triticum sativa), radish (Raphanus sativus), cucumber (Cucumus sativus), and Echinochloa crusgalli (L.) Beauv; (2) Field trials with four weeds: E. crusgalli, Eleusine indica (L.) Gaertn, Alternanthera philoxeroides (Mart.) Griseb, and Conyza canadensis (L.) Cronq. Greenhouse tests showed that the efficacy of PAs and acetic acid (AA) to control four test plants increased with the increasing of PAs concentration. The inhibition rates of four tested PAs (FBV (0.6-9.2% AA + (0.3-5.0% tar), HWV (0.2-1.8% AA + 0.3-4.3% tar), ASV (0.5-8.7% AA + 0.4-7.0% tar), and CWV (0.7-5.3% AA + 0.5-7.5% tar) gave inhibition rates of 56 ± 4-97 ± 2%, 21 ± 2-90 ± 6%, 29 ± 3-98 ± 5%, and 44 ± 6-86 ± 2%, respectively, and the field effects of PAs against four weeds were enhanced with the increasing of concentrations and time after spraying (1 to 14 days). Their control effects against E. crusgalli, E. indica, A. philoxeroides, and C. canadensis were 4 ± 1-93 ± 4%, 7 ± 3-90 ± 3%, 32 ± 2-95 ± 3%, and 31 ± 5-96 ± 4%, respectively. The mixed effect of the four PAs was higher than the same dose of AA. These results will help to determine the potential of PAs to be developed as non-selective herbicides to control weeds in organic farming.

Discovery of novel natural products for mosquito control

Vector control plays a key role in reducing the public health burden of mosquito-borne diseases. Today's vector control strategies largely rely on synthetic insecticides that can have a negative environmental impact when applied outdoors and often become inefficient because of the mosquitoes' ability to develop resistance. An alternative and promising approach to circumvent these challenges involves the implementation of insecticides derived from nature (biopesticides) for vector control. Biopesticides can constitute naturally occurring organisms or substances derived from them that have lifespan-shortening effects on disease vectors such as mosquitoes. Here we present the discovery and evaluation of natural product-based biological control agents that can potentially be developed into biopesticides for mosquito control. We screened a natural product collection comprising 390 compounds and initially identified 26 molecules with potential ability to kill the larval stages of the yellow fever mosquito Aedes aegypti, which is responsible for transmitting viruses such as dengue, Zika, chikungunya and yellow fever. Natural products identified as hits in the screen were further evaluated for their suitability for biopesticide development. We show that a selection of the natural product top hits, bactobolin, maytansine and ossamycin, also killed the larval stages of the malaria-transmitting mosquito Anopheles gambiae as well as the adult form of both species. We have further explored the usefulness of crude extracts and preparations from two of the best candidates' sources (organisms of origin) for mosquitocidal activity, that is extracts from the two bacteria Burkholderia thailandensis and Streptomyces hygroscopicus var. ossamyceticus.

You are what you eat: fungal metabolites and host plant affect the susceptibility of diamondback moth to entomopathogenic fungi

Background

Beauveria are entomopathogenic fungi of a broad range of arthropod pests. Many strains of Beauveria have been developed and marketed as biopesticides. Beauveria species are well-suited as the active ingredient within biopesticides because of their ease of mass production, ability to kill a wide range of pest species, consistency in different conditions, and safety with respect to human health. However, the efficacy of these biopesticides can be variable under field conditions. Two under-researched areas, which may limit the deployment of Beauveria-based biopesticides, are the type and amount of insecticidal compounds produced by these fungi and the influence of diet on the susceptibility of specific insect pests to these entomopathogens.

Methods

To understand and remedy this weakness, we investigated the effect of insect diet and Beauveria-derived toxins on the susceptibility of diamondback moth larvae to Beauveria infection. Two New Zealand-derived fungal isolates, B. pseudobassiana I12 Damo and B. bassiana CTL20, previously identified with high virulence towards diamondback moth larvae, were selected for this study. Larvae of diamondback moth were fed on four different plant diets, based on different types of Brassicaceae, namely broccoli, cabbage, cauliflower, and radish, before their susceptibility to the two isolates of Beauveria was assessed. A second experiment assessed secondary metabolites produced from three genetically diverse isolates of Beauveria for their virulence towards diamondback moth larvae.

Results

Diamondback moth larvae fed on broccoli were more susceptible to infection by B. pseudobassiana while larvae fed on radish were more susceptible to infection by B. bassiana. Furthermore, the supernatant from an isolate of B. pseudobassiana resulted in 55% and 65% mortality for half and full-strength culture filtrates, respectively, while the filtrates from two other Beauveria isolates, including a B. bassiana isolate, killed less than 50% of larvae. This study demonstrated different levels of susceptibility of the insects raised on different plant diets and the potential use of metabolites produced by Beauveria isolates in addition to their conidia.

Lantadene A and boswellic acid isolated from the leaves of Lantana camara L. have the potential to control phytopathogenic Fusarium species

Phytopathogenic Fusarium species are restricting factors causing diseases and yield loss in crop production. As part of exploration for pesticides from medicinal plants, this study aimed to isolate and characterize bioactive compounds from Lantana camara L. and evaluate their efficiency against Fusarium phytopathogens. Phytochemical investigation of ethyl acetate leaf extract led to separation of lantadene A (22-angeloyloxy-9-hydroxy-3-oxo-olean-12-en-28-oic acid) and boswellic acid (11-keto-β-boswellic acid). The chemical structures of the aforementioned compounds were confirmed using physical properties, spectroscopic analysis, and published data. Lantadene A exhibited significant antifungal activity against F. subglutinans, F. proliferatum, F. solani, F. graminearum, and F. semitectum with minimum inhibitory concentration (MIC) less than or equal to 0.63 mg/mL. Boswellic acid exhibited strong activity (MIC = 0.63 mg/mL) against F. subglutinans and F. semitectum. In terms of their toxicity towards Raw 264.7 cells, lantadene A and boswellic acid recorded half-maximal inhibitory concentration values of 84.2 μg/mL and 186.6 μg/mL, respectively. Both lantadene A and boswellic acid had no phytotoxic effect against seed germination and seedling root length. Lantadene A and boswellic acid have strong potential to be further investigated as lead natural fungicides (biopesticides) to control Fusarium crop diseases.

Cladophialophora bantiana metabolites are efficient in the larvicidal and ovicidal control of Aedes aegypti, and Culex quinquefasciatus and have low toxicity in zebrafish embryo

Mosquitoes' current insecticide resistance status in available public health insecticides is a serious threat to mosquito control initiatives. Microbe-based control agents provide an alternative to conventional pesticides and insecticides, as they can be more targeted than synthetic insecticides. The present study was focused on identifying and investigating the mosquitocidal potential of Cladophialophora bantiana, an endophytic fungus isolated from Opuntia ficus-indica. The Cladophialophora species was identified through phylogenetic analysis of the rDNA sequence. The isolated fungus was first evaluated for its potential to produce metabolites against Aedes aegpti and Culex quinquefasciatus larvae in the 1-4th instar. The secondary metabolites of mycelium extract were assessed at various test doses (100, 200, 300, 400, and 500 μg/mL) in independent bioassays for each instar of selected mosquito larvae. After 48 h of exposure, A. aegypti expressed LC₅₀ values of 13.069, 18.085, 9.554, and 11.717 μg/mL and LC₉₀ = 25.702, 30.860, 17.275, and 19.601 μg/mL; followed by C. quinquefasciatus LC₅₀ = 14.467, 11.766, 5.934, and 7.589 μg/mL, and LC₉₀ = 29.529, 20.767, 11.192, and 13.296 μg/mL. The mean % of ovicidal bioassay was recorded 120 h after exposure. The hatchability (%) was proportional to mycelia metabolite concentration. The enzymatic level of acetylcholinesterase in fungal mycelial metabolite treated 4th instar larvae indicated a dose-dependent pattern. The GC-MS profile of C. bantiana extracts identified five of the most abundant compounds, namely cyclobutane, trans-3-undecene-1,5-diyne, 1-bromo-2-chloro, propane, 1,2,3-trichloro-2-methyl-, 5,5,10,10-tetrachlorotricyclo, and phenol, which had the killing effect in mosquitoes. Furthermore, the C. bantiana fungus ethyl acetate extracts had a strong larvicidal action on A. aegypti and C. quinquefasciatus. Finally, the toxicity test on zebrafish embryos revealed the induction of malformations only at concentrations above 1 mg/mL. Therefore, our study pioneered evidence that C. bantiana fungal metabolites effectively control A. aegypti and C. qunquefasciastus and show less lethality in zebrafish embryos at concentrations up to 500 μg/mL.

Cooperative game theory approach to develop an incentive mechanism for biopesticide adoption through farmer producer organizations

Biopesticides have been recognized as viable alternatives to chemical pesticides in controlling agricultural pests for plants and reducing harmful chemical residues. However, small and marginal farmers are facing challenges while adopting biopesticides, namely, high cost and complicated application techniques, resulting in a low level of farmer acceptance. Accordingly, Farmer Producer Organizations (FPOs), voluntarily formed by farmers, develop mutual technical assistance among their members to solve the technical problems of biopesticide adoption. This study assumes that as a new form of farmer cooperative, FPOs have the potential to promote biopesticide adoption through the implementation of collective pesticide adoption (CPA). Along this line, this paper uses a cooperative game-based hybrid method to develop an incentive mechanism of biopesticide adoption for FPOs to implement CPAs. First, we construct a CPA decision model for mixed pesticides (i.e., biopesticides and chemical pesticides) based on multichoice goal programming (MCGP) to compromise the conflicting objectives regarding cost efficiency and chemical residue reduction, thereby obtaining the optimal total cost of pesticide adoption. Second, recognizing the optimal total adoption cost as a baseline, we devise a cooperative game-based cost allocation scheme to maintain farmers' voluntary participation in FPOs. This study demonstrates that the CPA implemented based on our proposed models can at least match if not surpass the economic and environmental performance of farmers' independent pesticide adoption (IPA). We further demonstrate that the proposed cooperative game solution is more suitable for the FPO's cost allocation issue than the eminent solutions, such as the Shapley value.

The genotoxic, cytotoxic and growth regulatory effects of plant secondary metabolite β-caryophyllene on polyphagous pest Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

Use of secondary metabolites as an alternative to organic pesticides is an eco-friendly and safe strategy in pest management. β-caryophyllene [(1R,4E,9S)-4,11,11-trimethyl-8-methylene bicyclo [7.2.0]undec-4-ene], a natural sesquiterpene is found as an essential oil in many plants like Syzygium aromaticum, Piper nigrum, Cannabis sativa. The present study aims at exploring the insecticidal, genotoxic and cytotoxic potential of β-caryophyllene against common cutworm Spodoptera litura (Fab.), a major polyphagous pest. S. litura larvae were fed on different concentrations (5, 25, 125, 625 and 3125 ppm) of β-caryophyllene. Results revealed delay in larval and pupal period with increase in concentration. Larval mortality increased and adult emergence declined significantly with increase in concentration. Higher concentrations of β-caryophyllene caused pupal and adult deformities. A negative impact of β-caryophyllene was also seen on the nutritional physiology of S. litura. Parameters such as relative growth rate, relative consumption rate, efficiency of conversion of ingested food, efficiency of conversion of digested food and approximate digestibility showed a significant reduction in a dose dependent manner. DNA damage assessed using comet assay revealed significant genotoxic effects at LC₃₀ and LC₅₀ concentrations. There was an increase in tail length, percent tail DNA, tail moment and olive tail moment. Phenol oxidase activity was suppressed at LC₅₀ concentration with respect to control. Total hemocyte count also declined significantly at LC₃₀ and LC₅₀ concentrations as compared to control. β-caryophyllene induced genotoxic and cytotoxic damage affecting the growth and survival of S. litura larvae. Our findings suggest that β-caryophyllene has the potential to be used for the management of insect pests.

Compatibility of the bacterial entomopathogen Pseudomonas protegens with the natural predator Chrysoperla carnea (Neuroptera: Chrysopidae)

The susceptibility of the green lacewing Chrysoperla carnea to the soil-dwelling bacterial entomopathogen Pseudomonas protegens CHA0 was investigated in this study. Laboratory bioassays were conducted on larval instars exposed to different bacterial concentrations by both direct feeding and indirectly by offering a pre-treated insect prey. Potential toxicity was assessed through dose-response bioassays, while possible sublethal effects were evaluated on immature development time and the reproductive performance (fecundity) of adults emerging from treated juveniles. As a result, no significant effects were observed on larval survival and development in a comparison between treated and untreated (control) groups. No significant impact on adult emergence and no detrimental effects on female fecundity were detected. Everything considered, the use of P. protegens in the agroecosystem appears to be compatible with chrysopids.

Isolation of a Novel Alphabaculovirus (Baculoviridae) from Automeris liberia (Cramer, 1780) (Lepidoptera: Saturniidae) in African Oil Palms in Brazil

A novel baculovirus observed to infect Automeris liberia (Cramer) (bullseye moth) is here described. Caterpillars of A. liberia with symptoms of viral infection were collected from African oil palm plantations in Tailândia, PA, Brazil. Macerated caterpillars were then offered to caterpillars of Automeris cinctistriga (Felder & Rogenhoper), leading to viral symptoms and death before pupation. A transmission electron microscope was used for virus ultrastructural identification. The presence of viral occlusion bodies (OBs) containing multiple nucleocapsids was observed and such features are compatible with Alphabaculovirus (Baculoviridae). Molecular detection by PCR with primers for polyhedrin gene (polh) and for late expression factor-8 gene (lef-8), confirmed that this isolate belonged to Alphabaculovirus genus. To our knowledge, this is the first record of a baculovirus isolated from or associated to Automeris. The name Automeris liberia nucleopolyhedrovirus (AuliNPV) is proposed for the new virus.

Biocontrol competence of Beauveria bassiana, Metarhizium anisopliae and Bacillus thuringiensis against tomato leaf miner, Tuta absoluta Meyrick 1917 under greenhouse and field conditions

Tomato is one of the most important crops grown under both greenhouse and field conditions throughout the world. Its production is highly challenged by infestation of leaf miner insect, Tuta absoluta Meyrick regardless of excessive insecticide application. The chemical insecticides results insect resistance, environmental pollution, and health problems and there is urgent need for management options such as integrated pest management (IPM) to obviate these problems. Thus, the present study aims to evaluate the effectiveness of single and combination treatments of entomopathogens; Beauveria bassiana, Metarhizium anisopliae, Bacillus thuringeinsis, and an insecticide against T. absoluta under greenhouse and field conditions. Two varieties (Awash and Venes) of tomato for greenhouse experiment and one (Gellila) variety for field experiment were used with Tutan36%SC (insecticide with active ingredient of Chlorphenapyr 36%SC) and untreated plots as positive and negative controls, respectively. The results showed significant leaf and fruit damage reduction in all the treatments. B. bassiana-AAUB03, M. anisopliae-AAUM78, and B. thuringiensis-AAUF6 showed the highest (93.4%, 89.7% and 90.1%) leaf and (93.5%, 94.4% and 95%) fruit protection under greenhouse condition. The combined treatments improved leaf protection efficacy up to 95.3% under field condition. When the entomopathogens were combined with half or quarter reduced concentrations of Tutan36% SC, it showed 94.4% of pest protection. In all the treatments, 72–96% of marketable fruit was obtained as par insecticide treatment scored 85–93%. All the entomopathogens did not cause any adverse effect on the growth of tomato rather improved shoot length, shoot branching, leaf and fruit numbers. Therefore, application of entomopathogens in single, consortium or in combination reduced the recommended concentration of Tutan36%SC to control T. absoluta.

Toxicity assessment of emamectin benzoate and its commercially available formulations in Pakistan by in vivo and in vitro assays

Emamectin benzoate (EMB) is generally considered a safe insecticide in agriculture and veterinary practices, yet, it can cause cytotoxic and genotoxic effects. Hence, the aim of this study was to evaluate toxic effects of 80% EMB and its commercially used formulations (Tycon 1.9% EC and Tycon plus 5% EW) in Pakistan and tested for acute toxicity in albino rats, rabbits and fish (Labeo rohita). Genotoxicity was investigated by in vivo comet assay and bone marrow micronucleues test in the rats. In vitro mutagenicity was tested in Salmonella typhimurium TA98 and TA100. The tested EMB formulations were found moderately toxic (oral LD₅₀: 122-168 mg/kg), causing severe eye irritation in rabbits, highly toxic to fish (LC₅₀: 9-43 μg/L) and found non mutagenic. Oral administrations of EMB (80% and 5%) at 100 mg/kg of body weight to male rats reduced red blood cells, hemoglobin, and slightly increased the blood glucose, urea and liver enzymes levels but had no significant damage to DNA. EMB induced bone marrow toxicity was observed as reduction of polychromatic erythrocytes. Overall, EMB exposure was highly toxic to fish, and caused hemo- and hepatotoxicity in rats. These findings warrant cautious use of EMB formulations in agrochemicals and veterinary medicine.

Streptomyces derivatives as an insecticide: Current perspectives, challenges and future research needs for mosquito control

The pervasiveness of arboviruses in wreaking havoc on public health has lingered on international health agendas. A scarcity of mosquito-borne disease vaccines and therapies demands prompt attention, as billions of people worldwide are at risk of infections. It is widely known that vector control continues, and in some diseases, remains the only resort in suppressing disease transmissions we presently possess at its disposal. But the use of commercial insecticides is being crippled by the widespread insecticide resistance, which greatly menaces their efficacies, toxicological repercussions such as environmental pollution and human health risk. Rather, an environmentally benign technique of employing Streptomyces isolates from settings such as terrestrial soils, marine sediments, and mangrove soils for Culicidae management has recently received a lot of positive attention. Streptomyces' capacities to produce a wide range of bioactive secondary metabolites that contribute to pharmaceutical, agricultural and veterinarian, Streptomyces-derived bioactive compounds are increasingly being considered for use in vector control. Herein, we compiled all of the available datasets on the effectiveness of Streptomyces-derived compounds against major mosquito vectors of medical importance. Aedes, Anopheles, and Culex are used to assess the toxicity of crude extracts or fractions. This paper reviewed the promising ovicidal, larvicidal, and pupacidal effects of different Streptomyces strains. Notably, no research into the adulticidal effect of Streptomyces-derived compounds has yet been done. Aside from the genetic makeup, the production of secondary metabolites from Streptomyces depends on the growing conditions. And that, to optimise the maximum yield of highly potent bioactive compounds being extracted, solvents' choice is of paramount importance. Thus, both cultivation parameters and the choice of organic solvents for secondary metabolites extraction will be discussed. Furthermore, biases derived from different studies have implied the need for standardizing experimental procedures. While entomological data should be collected consistently across all studies to expedite evidence-based policymaking of bioinsecticides, the quality of data from vector control interventions - particularly the experimental design, execution, analysis, and presentation of results of vector control studies - will be thoroughly reviewed. Lastly, to promote consistency and reliability, these knowledge gaps are identified, along with a discussion of current perspectives on vector control, global bioinsecticide trends, challenges on commercializing bioinsecticides and future research needs.

Plant immunity inducers: from discovery to agricultural application

While conventional chemical fungicides directly eliminate pathogens, plant immunity inducers activate or prime plant immunity. In recent years, considerable progress has been made in understanding the mechanisms of immune regulation in plants. The development and application of plant immunity inducers based on the principles of plant immunity represent a new field in plant protection research. In this review, we describe the mechanisms of plant immunity inducers in terms of plant immune system activation, summarize the various classes of reported plant immunity inducers (proteins, oligosaccharides, chemicals, and lipids), and review methods for the identification or synthesis of plant immunity inducers. The current situation, new strategies, and future prospects in the development and application of plant immunity inducers are also discussed.

Enzymatic hydrolysis of the organic fraction of municipal solid waste: Optimization and valorization of the solid fraction for Bacillus thuringiensis biopesticide production through solid-state fermentation

To reach a more sustainable society, the implementation of a circular economy perspective in municipal waste management becomes essential. In this work, the enzymatic hydrolysis of source-separated organic fraction of municipal solid waste (OFMSW) has been optimized as a sugar-releasing step. A liquid sugar concentrate, with a maximum reducing sugar concentration of 50.56 g L^-1, and a solid hydrolyzed fraction were obtained. The effect of the harshness of the hydrolysis conditions was evaluated on the performance of the resulting solid fraction as a substrate for Bacillus thuringiensis biopesticide production through solid-state fermentation. A production of 3.9 × 10⁸ viable cells g^-1 dry matter with a 33% sporulation ratio was achieved for milder hydrolysis conditions, highlighting the potential of the solid fraction of hydrolysis as a substrate of SSF processes. The proposed valorization pathway for the OFMSW results in a sugar concentrate with potential for fermentative processes and a fermented solid containing biopesticides from Bacillus thuringiensis.

Effects of Chitosan and Silica Nanoparticles Against the Development and Growth of Red Chilli Anthracnose Disease Colletotrichum sp

<b>Background and Objective:</b> <i>Colletotrichum</i> sp., is a pathogen that causes anthracnose disease that can reduce chilli production. One environmentally for controlling plant disease can be done using chitosan and silica nanotechnology. This study aimed to test the ability of chitosan and silica nanoparticles to inhibit the growth of <i>Colletotrichum</i> sp. and suppress the development of the diseases on chilli seeds. <b>Materials and Methods:</b> This research consisted of the pathogenicity test of chitosan and silica nanoparticles and chilli seed germination inhibition test to control the development of <i>Colletotrichum</i> sp., using a completely randomized design within 10 treatments and 3 replications. <b>Results:</b> The results showed that 100 ppm chitosan nanoparticles inhibited the growth of <i>Colletotrichum</i> sp. and conidia germination with inhibition percentages of 92.20 and 99.4%, respectively. In addition, the development of anthracnose on chilli seed germination has been suppressed by 93% at a 100 ppm concentration of silica nanoparticles. <b>Conclusion:</b> In conclusion, both single or mixed formulations of chitosan and silica nanoparticles were able to inhibit the growth and development of <i>Colletotrichum </i>sp. and increase the chilli seed viability.

Production, characterization and pesticidal potential of Bacillus species metabolites against sugar ant (Camponotus consobrinus)

The use of biopesticides in pest management and pre-harvest disease and crop pest control have been advocated in recent years. This is because of their eco-friendliness and suitability for pest control in the agricultural industry. The objective of this study was to determine the antibacterial and pesticidal potential against sugar ant of metabolites produced by Bacillus species. The species were B. proteolyticus, B. thuringensis, B. cereus and B. subtilis. Metabolite production was carried out in batch experimental setup. The inoculated flasks were incubated in an incubator shaker for 120 h at temperature of 37 °C ± 2 °C. Metabolite extraction was carried out using the acid precipitation method. The crude metabolites were characterized using Fourier Transform Infrared (FTIR) and Gas Chromatography Mass Spectroscopy (GC-MS). Antibacterial activity of the metabolites was carried out both in agar and broth media while pesticidal potential was carried out using the diet-fed approach. All the metabolites showed antibacterial activity against the test pathogens used for investigation. This was irrespective of whether they were used singly or in combination. Generally, the rate of kill of the sugar ants by the respective metabolites was directly proportional to metabolite concentration in the diet. In the control diet setup with no added metabolite, no mortality was recorded throughout the period of incubation. The study findings gave an indication of the potential of these metabolites for possible control of phytopathogens.

Oral toxicity of various Stemona collinsiae crude extracts against nymph and adult stages of American cockroach, Periplaneta americana (Dictyoptera: Blattodea)

Stemona collinsiae exhibits insecticidal resistance against various pests and insect vectors. However, insecticidal activity of S. collinsiae roots has not been tested for some insect vectors, including the American cockroach, Periplaneta americana. The synanthropic insect P. americana is a reservoir of pathogenic and non-pathogenic microorganisms and a cause of infectious diseases and cockroach allergy. This important vector transmits microorganisms to animals and humans to cause vector-borne diseases. This research involved detection of the nymphicidal and adulticidal activities of S. collinsiae root extracts against P. americana through oral administration. The effects of hexane, dichloromethane, ethanol, and water crude extracts were tested on final instar nymphs and adult P. americana. After P. americana ingested bait containing hexane and dichloromethane crude extracts, signs of toxicity occurred, such as hind leg shaking, whole-body tremor, immobility, abdomen swelling, and death. At 48 h, the nymphs and adult P. americana that ingested dichloromethane crude extract-containing bait showed corrected mortality of 65%-100% and 20%-100%, respectively. Whereas none of the nymphs and adult P. americana that ingested the water crude extract-containing bait died (0% corrected mortality). When we dissected alimentary canals of the dead P. americana that had ingested dichloromethane and hexane crude extract-containing baits, the foreguts were found to be swollen. TLC analysis showed the dichloromethane and hexane crude extracts contained the alkaloid didehydrostemofoline and unknown fluorescent substances. Phytochemicals from crude extracts were detected in extracts of dissected alimentary canals using thin-layer chromatography, and didehydrostemofoline alkaloid and unknown fluorescent substances were found in cockroaches that ingested dichloromethane- and hexane-containing baits. The cause of death of P. americana may be attributed to alkaloids and synergistic effects of other substances in S. collinsiae root extract. Mechanisms of action might include several pathways involved in nervous system function. Thus, dichloromethane and hexane crude extracts can be developed as alternative active ingredients in a natural insecticide for cockroach control.

Commercialization, Diffusion and Adoption of Bioformulations for Sustainable Disease Management in Indian Arid Agriculture: Prospects and Challenges

Trichoderma spp. is one of the most popular genus of fungi commercially available as a plant growth promoting fungus (PGPF) and biological control agent. More than 80 species of Trichoderma are reported in the literature. However T. asperellum, T. harzianum, T. viride, and T. virens are most commonly utilized as biocontrol agents. Studies were initiated to explore the potential of biocontrol agents in order to develop a cost effective and practical management strategy. Analysis of large number of soil samples collected from western parts of the region led to isolation of native biocontrol agents viz., Trichoderma harzianum, Aspergillus versicolor, and Bacillus firmus from different agricultural systems. These biocontrol agents have proved their antagonistic ability in laboratory tests and field trials. In India, two species of Trichoderma i.e., T. viride and T. harzianum are commercially registered for usage against soil borne plant pathogens mostly as a seed treatment or soil application. There are published scientific papers on the efficacy of T. asperellum and T. virens in India for suppressing pathogens but these are not yet registered under Central Insecticide Board and Registration Committee (CIB & RC). This review article focuses on the uses, commercialization and adoption issues of various fungal and bacterial consortium products in sustainable disease management.

Microbial chitinases: properties, enhancement and potential applications

Chitinases are a category of hydrolytic enzymes that catalyze chitin and are formed by a wide variety of microorganisms. In nature, microbial chitinases are primarily responsible for chitin decomposition and play a vital role in the balance of carbon and nitrogen ratio in the ecosystem. The physicochemical attributes and the source of chitinase are the main bases that determine their functional characteristics and hydrolyzed products. Several chitinases have been reported and characterized, and they obtain a wider consideration for their utilization in a large number of uses such as in agriculture, food, environment, medicine and pharmaceutical companies. The antifungal and insecticidal impacts of several chitinases have been extensively studied, aiming to protect crops from phytopathogenic fungi and insects. Chitooligosaccharides synthesized by chitin degradation have been shown to improve human health through their antimicrobial, antioxidant, anti-inflammatory and antitumor properties. This review aims at investigating chitinase production, properties and their potential applications in various biotechnological fields.

Evaluating the biocontrol potential of Canadian strain Bacillus velezensis 1B-23 via its surfactin production at various pHs and temperatures

BACKGROUND

Microorganisms, including Bacillus species are used to help control plant pathogens, thereby reducing reliance on synthetic pesticides in agriculture. Bacillus velezensis strain 1B-23 has been shown to reduce symptoms of bacterial disease caused by Clavibacter michiganensis subsp. michiganensis in greenhouse-grown tomatoes, with in vitro studies implicating the lipopeptide surfactin as a key antimicrobial. While surfactin is known to be effective against many bacterial pathogens, it is inhibitory to a smaller proportion of fungi which nonetheless cause the majority of crop diseases. In addition, knowledge of optimal conditions for surfactin production in B. velezensis is lacking.

RESULTS

Here, B. velezensis 1B-23 was shown to inhibit in vitro growth of 10 fungal strains including Candida albicans, Cochliobolus carbonum, Cryptococcus neoformans, Cylindrocarpon destructans Fusarium oxysporum, Fusarium solani, Monilinia fructicola, and Rhizoctonia solani, as well as two strains of C. michiganensis michiganensis. Three of the fungal strains (C. carbonum, C. neoformans, and M. fructicola) and the bacterial strains were also inhibited by purified surfactin (surfactin C, or [Leu7] surfactin C15) from B. velezensis 1B-23. Optimal surfactin production occurred in vitro at a relatively low temperature (16 °C) and a slightly acidic pH of 6.0. In addition to surfactin, B. velenzensis also produced macrolactins, cyclic dipeptides and minor amounts of iturins which could be responsible for the bioactivity against fungal strains which were not inhibited by purified surfactin C.

CONCLUSIONS

Our study indicates that B. velezensis 1B-23 has potential as a biocontrol agent against both bacterial and fungal pathogens, and may be particularly useful in slightly acidic soils of cooler climates.

Rhamnolipids inhibit aflatoxins production in Aspergillus flavus by causing structural damages in the fungal hyphae and down-regulating the expression of their biosynthetic genes

Aflatoxins are hepatotoxic and carcinogenic fungal secondary metabolites that usually contaminate crops and represent a serious health hazard for humans and animals worldwide. In this work, the effect of rhamnolipids (RLs) produced by Pseudomonas aeruginosa #112 on the growth and aflatoxins production by Aspergillus flavus MUM 17.14 was studied in vitro. At concentrations between 45 and 1500 mg/L, RLs reduced the mycelial growth of A. flavus by 23-40% and the production of aflatoxins by 93.9-99.5%. Purified mono-RLs and di-RLs exhibited a similar inhibitory activity on fungal growth. However, the RL mixture had a stronger inhibitory effect on aflatoxins production at concentrations up to 190 mg/L, probably due to a synergistic effect resulting from the combination of both congeners. Using transmission electron microscopy, it was demonstrated that RLs damaged the cell wall and the cytoplasmic membrane of the fungus, leading to the loss of intracellular content. This disruptive phenomenon explains the growth inhibition observed. Furthermore, RLs down-regulated the expression of genes aflC, aflE, aflP and aflQ involved in the aflatoxins biosynthetic pathway (6.4, 44.3, 38.1 and 2.0-fold, respectively), which is in agreement with the almost complete inhibition of aflatoxins production. Overall, the results herein gathered demonstrate for the first time that RLs could be used against aflatoxigenic fungi to attenuate the production of aflatoxins, and unraveled some of their mechanisms of action.

Efficacy of Ocimum tenuiflorum essential oil as grain protectant against coleopteran beetle, infesting stored pulses

In the present investigation, essential oil (EO) of Ocimum tenuiflorum and its principal constituent (eugenol) was evaluated for its toxicity and mode of action against Callosobruchus maculatus. Furthermore, fumigant toxicity and germination studies on the application of O. tenuiflorum EO and eugenol against C. maculatus on different pulses was also studied. Fumigant activity studies revealed that EO toxicity was significantly (p < 0.05) influenced by concentration and exposure time. In fumigant toxicity assay without food, O. tenuiflorum EO and eugenol showed LC50 value of 278.6 and 256.5 µL/L air, respectively, at one hour exposure. Further, O. tenuiflorum EO displayed fumigant toxicity via inhibiting acetylcholinesterase activity. Pulses treated with O. tenuiflorum EO showed 70% of C. maculatus mortality at 250 µL/L air concentration after 24 h. Furthermore, these treatments didn't affect the seed viability of the pulses tested. Hence, the application of O. tenuiflorum EO has potential scope as a botanical insecticide.

Comparing the efficacy of nutmeg essential oil and a chemical pesticide against Musca domestica and Chrysomya albiceps for selecting a new insecticide agent against synantropic vectors

The insecticidal activity of Myristica fragrans (Houtt) essential seed oil, (Nutmeg) was evaluated against Musca domestica (Linnaeus) and Chrysomya albiceps (Wiedemann); both important infectious pathogenic disease vectors. The oil was extracted by distillation, and 21 components were identified during chemical analysis; principally β-pinene (26%), α-pinene (10.5%), Sabinene (9.1%) and γ-terpinen (8.5%). Insecticidal properties were identified through larvicide and adulticide tests. Using the immersion method, the oil at 5% was found to be very effective (90 ± 1%) against M. domestica larvae. The results for adulticide activity varied by fly species, dosage, time, and method of exposure. Topical application (on the insect thorax) was more toxic to C. albiceps, where the lethal concentration at 50% (LC₅₀) was 2.02 ± 0.56, and 8.57 ± 2.41 for the common flies. When the insects were exposed to oil impregnated paper, the results were similar for M. domestica and C. albiceps adults with respective LC₅₀ values of 2.74 ± 0.24, and 3.65 ± 0.48. Thus, the results demonstrated that M. fragrans oil presents insecticidal activity and can be used for control of Musca domestica and Chrysomya albiceps.

Karanjin

Karanjin [IUPAC: 3-methoxy-2-phenylfuro-(2,3-h-chrome-4-ol)], a bioactive furanoflavonoid and a potent biomolecule, was first isolated from Pongamia pinnata (L.). The crude extracts from root, leaf and seed having active constituent karanjin is highly valued in both traditional and modern knowledge systems. This review highlights, critically assesses, and presents the probable biosynthetic pathways of karanjin and its isolation methodologies with a view to actualizing its full potential. Karanjin exhibits multiple health benefits and applications, with evident anti-diabetic, anti-cancer, anti-inflammatory, anti-hyperglycemic, antioxidant, anti-colitis, anti-ulcer, and anti-Alzheimer properties. Consequently, the physiochemical properties and biological effects of karanjin have been detailed and analyzed. The efficacy of karanjin has been attenuated by toxicological studies that have proven karanjin to be non-toxic at physiological conditions as substantiated by in vitro and in vivo studies. In addition, the multiple insect repellent/insecticidal properties of karanjin and its availability as an acaricide/bio-insecticide have been reviewed. This review article underscores and endorses the immense potential for novel drug leads in various medicinal and industrial applications, suggesting a deeper insight into its metabolic fate, bioavailability, and cellular effects that await further investigations.

Multifaceted interactions between the pseudomonads and insects: mechanisms and prospects

Insects and bacteria are the most widespread groups of organisms found in nearly all habitats on earth, establishing diverse interactions that encompass the entire range of possible symbiotic associations from strict parasitism to obligate mutualism. The complexity of their interactions is instrumental in shaping the roles of insects in the environment, meanwhile ensuring the survival and persistence of the associated bacteria. This review aims to provide detailed insight on the multifaceted symbiosis between one of the most versatile bacterial genera, Pseudomonas (Gammaproteobacteria: Pseudomonadaceae) and a diverse group of insect species. The Pseudomonas engages with varied interactions with insects, being either a pathogen or beneficial endosymbiont, as well as using insects as vectors. In addition, this review also provides updates on existing and potential applications of Pseudomonas and their numerous insecticidal metabolites as biocontrol agents against pest insects for the improvement of integrated pest management strategies. Here, we have summarized several known modes of action and the virulence factors of entomopathogenic Pseudomonas strains essential for their pathogenicity against insects. Meanwhile, the beneficial interactions between pseudomonads and insects are currently limited to a few known insect taxa, despite numerous studies reporting identification of pseudomonads in the guts and haemocoel of various insect species. The vector-symbiont association between pseudomonads and insects can be diverse from strict phoresy to a role switch from commensalism to parasitism following a dose-dependent response. Overall, the pseudomonads appeared to have evolved independently to be either exclusively pathogenic or beneficial towards insects.