Microbial Biopesticides Research Articles

Modeling and Optimization of Gas Sparging-Assisted Bacterial Cultivation Broth Microfiltration by Response Surface Methodology and Genetic Algorithm.

Production of highly efficient biomass-based microbial biopesticides significantly depends on downstream processing in terms of obtaining as high concentration of viable cells as possible. Microfiltration is one of the recommended operations for microbial biomass separation, but its main limitation is permeate flux decrease due to the membrane fouling. The effect of air sparging as a hydrodynamic technique for improvement of permeate flux during microfiltration of Bacillus velezensis cultivation broth was investigated. Modeling of the microfiltration was performed using the response surface methodology, while desirability function approach and genetic algorithm were applied for optimization, i.e., maximization of permeate flux and minimization of specific energy consumption. The results have revealed antagonistic relationship between the investigated dependent variables. The optimized values of superficial feed velocity and transmembrane pressure were close to the mean values of the investigated value ranges (0.68 bar and 0.96 m/s, respectively), while the optimized value of superficial air velocity had a more narrow distribution around 0.25 m/s. The results of this study have revealed a significant improvement of microfiltration performance by applying air sparging, thus this flux improvement method should be further investigated in downstream processing of different bacterial cultivation broths.

Characterisation of the Antibiotic Profile of Lysobacter capsici AZ78, an Effective Biological Control Agent of Plant Pathogenic Microorganisms.

Determining the mode of action of microbial biocontrol agents plays a key role in their development and registration as commercial biopesticides. The biocontrol rhizobacterium Lysobacter capsici AZ78 (AZ78) is able to inhibit a vast array of plant pathogenic oomycetes and Gram-positive bacteria due to the release of antimicrobial secondary metabolites. A combination of MALDI-qTOF-MSI and UHPLC-HRMS/M was applied to finely dissect the AZ78 metabolome and identify the main secondary metabolites involved in the inhibition of plant pathogenic microorganisms. Under nutritionally limited conditions, MALDI-qTOF-MSI revealed that AZ78 is able to release a relevant number of antimicrobial secondary metabolites belonging to the families of 2,5-diketopiperazines, cyclic lipodepsipeptides, macrolactones and macrolides. In vitro tests confirmed the presence of secondary metabolites toxic against Pythium ultimum and Rhodococcus fascians in AZ78 cell-free extracts. Subsequently, UHPLC-HRMS/MS was used to confirm the results achieved with MALDI-qTOF-MSI and investigate for further putative antimicrobial secondary metabolites known to be produced by Lysobacter spp. This technique confirmed the presence of several 2,5-diketopiperazines in AZ78 cell-free extracts and provided the first evidence of the production of the cyclic depsipeptide WAP-8294A2 in a member of L. capsici species. Moreover, UHPLC-HRMS/MS confirmed the presence of dihydromaltophilin/Heat Stable Antifungal Factor (HSAF) in AZ78 cell-free extracts. Due to the production of HSAF by AZ78, cell-free supernatants were effective in controlling Plasmopara viticola on grapevine leaf disks after exposure to high temperatures. Overall, our work determined the main secondary metabolites involved in the biocontrol activity of AZ78 against plant pathogenic oomycetes and Gram-positive bacteria. These results might be useful for the future development of this bacterial strain as the active ingredient of a microbial biopesticide that might contribute to a reduction in the chemical input in agriculture.

PESTICIDES AND INDIAN AGRICULTURE- A REVIEW

Globally more than half of the pesticides are utilized in Asia. India stands 12th in pesticide use globally and 3rd in Asia after China and Turkey. In present study, the data of different types of pesticides, pesticide use pattern and detailed pesticide consumption of the India and world were collected, organized and summarized. Agriculture is the most important sector of the Indian economy providing employment and livelihood to nearly 70% of the total population. And pesticides are an integral part of modern agriculture. Insecticides, fungicides and herbicides are commonly used for pest control in agriculture. However, insecticides form the highest share in total pesticide use in India. India share only1% of the global pesticide use. India has utilized around 58160 tonnes of pesticide in 2018. Per hectare application rate of pesticide was 0.31 kg in 2017. Despite a low per hectare use of pesticides in India, their injudicious use has led to the presence of residues in both biotic and abiotic sections of the environment. The advance research and development in the field of bio-pesticides applications greatly reduce the environmental pollution caused by the chemical synthetic insecticides residues and promotes sustainable development of agriculture. In India numerous bio-pesticides presently being developed may be exceptional replacements to chemical pesticides. There are many eco-friendly plant based and microbial bio-pesticides available in the market. Bio-pesticides consumption is only 8% in India. For sustainable agricultural development and to protect environment from adverse effect of chemical pesticides, formulation and utilization of bio-pesticides should be prompted.

ANALYSIS OF INDIAN AND CANADIAN LAWS REGULATING THE BIOPESTICIDES: A COMPARISON

An excessive use of toxic plant protection chemicals has irreversibly damaged the soil biology of agroecosystems, resulting in a substantial decline of productivity. Biocontrol agents, especially microbial biopesticides, are seen as one of the key solutions to overcome toxicity and pest resistance issues. Biopesticides are defined as mass-produced agents manufactured from living microorganisms or natural products used for the control of pests. Laws to regulate biopesticides both in India and Canada need to be analysed from the perspectives of trade facilitation, ease of business, proliferation of green technologies and products, and the sustainability and revitalization of soil biology. Registration of new biopesticides for its manufacturing, trade, import, storage, transport, disposal and safety is discussed from the point of view of the legal barriers imposed on the production process and trade. Having compared laws of both countries, authors offer recommendations for legal reform.

Efficacy of biopesticides against the whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), on parthenocarpic cucumber grown under protected environment in India

BackgroundThe whitefly, Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae), is one of the most damaging pests of crops grown in open field and under protected conditions. Owing to the indiscriminate use of insecticides, whitefly has developed resistance against various insecticides belonging to different chemical groups. Use of microbial biopesticides (entomopathogenic fungi) can be an effective alternate to chemical insecticides.ResultsThis study was planned for the evaluation of entomopathogenic fungi (EPF) formulations, namely, Beauveria bassiana Balsamo (Vuillemin), Lecanicillium lecanii (Zimmerman) Viegas and Metarhizium anisopliae (Metschnikoff) Sorokin and botanical pesticide, Neem Baan, for the management of different life stages of B. tabaci on parthenocarpic cucumber grown under protected conditions. The liquid formulations of Neem Baan at 10 and 15 ml/l were the most effective (90.7 to 93.3% in eggs, 93.3 to 97.1% in nymphs, and 92.4 to 94.2% reduction in whitefly adults after 3rd spray, respectively) as compared to EPF. Among the EPF, L. lecanii and B. bassiana at 10 and 15 ml/l (80.6 to 86.5% in eggs, 85.7 to 91.5% in nymphs, and 58.5 to 69.2% in whitefly adults after 3rd spray, respectively) were found to be more effective than M. anisopliae at 10 and 15 ml/l (78.4 to 82.8% in eggs, 82.5 to 85.9% in nymphs, and 57.7 to 62.8% in whitefly adults after third spray, respectively) in reducing different life stages of B. tabaci on cucumber. Significantly high yield of cucumber fruits was obtained from the plot where Neem Baan at 10 and 15 ml/l (2337.5 to 2420.8 g/plant) was used. Minimum fruit yield were recorded in untreated control plots.ConclusionsThe integration of these biopesticides in the management schedule of the whitefly under protected conditions will enhance the quality and market value of parthenocarpic cucumbers.

Characterization of Bacillus velezensis AK-0 as a biocontrol agent against apple bitter rot caused by Colletotrichum gloeosporioides

Bacillus genus produces several secondary metabolites with biocontrol ability against various phytopathogens. Bacillus velezensis AK-0 (AK-0), an antagonistic strain isolated from Korean ginseng rhizospheric soil, was found to exhibit antagonistic activity against several phytopathogens. To further display the genetic mechanism of the biocontrol traits of AK-0, we report the complete genome sequence of AK-0 and compared it with complete genome sequences of closely related strains. We report the biocontrol activity of AK-0 against apple bitter rot caused by Colletotrichum gloeosporioides, which could lead to commercialization of this strain as a microbial biopesticide in Korea. To retain its biocontrol efficacy for a longer period, AK-0 has been formulated with ingredients for commercialization, named AK-0 product formulation (AK-0PF). AK-0PF played a role in the suppression of the mycelial growth of the fungicide-resistant pathogen C. gloeosporioides YCHH4 at a greater level than the non-treated control. Moreover, AK-0PF exhibited greater disease suppression of bitter rot in matured under field conditions. Here, we report the complete genome sequence of the AK-0 strain, which has a 3,969,429 bp circular chromosome with 3808 genes and a G+C content of 46.5%. The genome sequence of AK-0 provides a greater understanding of the Bacillus species, which displays biocontrol activity via secondary metabolites. The genome has eight potential secondary metabolite biosynthetic clusters, among which, ituD and bacD genes were expressed at a greater level than other genes. This work provides a better understanding of the strain AK-0, as an effective biocontrol agent (BCA) against phytopathogens, including bitter rot in apple.

Green Technology Kills Nasty Fleas: Scientists are Getting Closer to Manufacturing New Forms of Highly Contagious Microbial Biopesticides to Exterminate Nasty Pests

The biology and genetic engineering experts are getting closer to the technological advancements for creating a safe and clean planet for our family. Biopesticides are extremely safer than chemical pesticides. Yearly, hundreds types of different humankind diseases getting transmitted to the other people through insect bites. A new form of biopesticide engineering shall be different from the other well known methods since this particular method mainly focuses on the mass widespread of the killer virus. Fleas are biological carriers of bacteria and viruses. And they attack the planet's population, the nature, and plants. These pests get seek, transmit the disease to a lot of other pests, and then die. Application of biopesticides at garbage sites, jungles, around populous and potential areas, and around the fleas living environment shall help the humanity to get rid of fleas bites and therefore a variety of dangerous diseases.

Tea Pest Management: A Microbiological Approach

Tea crop damage is caused by mites and insect pests, and each year a significant amount of crop loss is occurring due to their damage. The efficiency of synthetic pesticides has permitted for their widespread usage as a control tool over several decades. Synthetic pesticides, on the other hand, have resulted in the development of insect pest resistance, pollution, and pesticide residues in the finished product, etc, forcing the planting community to look for the development of an alternate strategy. Microbial pesticides have been employed to counter the mite and insect pest-damaging tendencies while a significant portion of scientific data suggests that their actions are both desirable and environmentally beneficial. The efficiency of entomopathogenic microorganisms against several tea pests was examined and the microbial biopesticides were found to be successful and demonstrated promising effects against tea pests. In this mini-review, we have combined fundamental and integrated pest management information into an easy-to-follow method for control the tea pests.

Integrated pest management options for the fall armyworm Spodoptera frugiperda in West Africa: Challenges and opportunities. A review

Introduction. The fall armyworm Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) is a voracious and generalist insect pest native to America. It was first detected in West Africa in 2016 and rapidly spread across the continent. The indiscriminate use of chemical insecticides poses risks to human health and threatens the few natural enemies present in these environments. Despite the existence of alternative control measures in America (e.g. genetically modified maize), efforts are needed to develop environmentally friendly approaches that are affordable for smallholder farmers and compatible with the African context. Literature. In this literature review, we describe the potential of the available alternative controls methods which include cultural, physical, biological and semiochemical strategies. The potential of their association is discussed considering their cost-benefice balance and local economic and agricultural context. Conclusions. Several affordable mitigation options could be implemented rapidly, pending proper communication efforts, including (i) the promotion of indigenous natural enemies by promoting refuges and training smallholder farmers on their identification; (ii) cultural methods, mainly by planting directly after the main rainfalls, as well as performing intercropping and crop rotation; and (iii) the use of microbial biopesticides, and avoiding some of the already identified ineffective chemical insecticides.

Advances in Entomopathogen Isolation: A Case of Bacteria and Fungi.

Entomopathogenic bacteria and fungi are quite frequently found in soils and insect cadavers. The first step in utilizing these microbes as biopesticides is to isolate them, and several culture media and insect baiting procedures have been tested in this direction. In this work, the authors review the current techniques that have been developed so far, in the last five decades, and display brief protocols which can be adopted for the isolations of these entomopathogens. Among bacteria, this review focuses on Serratia spp. and bacteria from the class Bacilli. Among fungi, the review focuses those from the order Hypocreales, for example, genera Beauveria, Clonostachys, Lecanicillium, Metarhizium, and Purpureocillium. The authors chose these groups of entomopathogenic bacteria and fungi based on their importance in the microbial biopesticide market.

Comparative Advantage of Using Biopesticides in Ukrainian Agroecosystems

The use of unsustainable levels of chemical fertilizers and plant protection chemicals has resulted in a steady decline in soil and crop productivity the world over. Soil biology has undergone irreversible damage, coupled with a high concentration of toxic chemical residues in plant tissues and human bodies. Agricultural practices must evolve to sustainably meet the growing global demand for food without irreversibly damaging soil. Microbial biocontrol agents have tremendous potential to bring sustainability to agriculture in a way that is safe for the environment. Biopesticides do not kill non-target insects, and biosafety is ensured because biopesticides act as antidotes and do not lead to chemical contamination in the soil. This article is part of a larger study conducted in Ukraine by researchers at the Université de Montréal with the support of Mitacs and Earth Alive Clean Technologies. The responses of farmers who use biofertilizers (“user farmers”) and those who do not (“non-user farmers”), along with the responses of manufacturers or suppliers of biofertilizers, and research and development (R&D) scientists are captured to demonstrate the advantages of applying microbial biopesticides to field crops. Participants reported a 15-30% increase in yields and crop production after the application of biopesticides. With the use of biopesticides, farmers cultivated better quality fruits, grains, and tubers with a longer shelf life. Moreover, while the risk of crop loss remains high (60-70%) with chemically grown crops, this risk is reduced to 33% on average if crops are grown using biopesticides. The findings indicate that a large proportion of farmers would prefer to use biopesticides if they are effective and high quality products. In this context, the quality and effectiveness of products is therefore very important. Despite their benefits to soil, human health, and ecosystems, biopesticides face significant challenges and competition vis-à-vis synthetic pesticides for a variety of reasons. Therefore, the development of biopesticides must overcome the problems of poor quality products, short shelf life, delayed action, high market costs, and legal/registration issues.

The Tripartite Interaction of Host Immunity-Bacillus thuringiensis Infection-Gut Microbiota.

Bacillus thuringiensis (Bt) is an important cosmopolitan bacterial entomopathogen, which produces various protein toxins that have been expressed in transgenic crops. The evolved molecular interaction between the insect immune system and gut microbiota is changed during the Bt infection process. The host immune response, such as the expression of induced antimicrobial peptides (AMPs), the melanization response, and the production of reactive oxygen species (ROS), varies with different doses of Bt infection. Moreover, B. thuringiensis infection changes the abundance and structural composition of the intestinal bacteria community. The activated immune response, together with dysbiosis of the gut microbiota, also has an important effect on Bt pathogenicity and insect resistance to Bt. In this review, we attempt to clarify this tripartite interaction of host immunity, Bt infection, and gut microbiota, especially the important role of key immune regulators and symbiotic bacteria in the Bt killing activity. Increasing the effectiveness of biocontrol agents by interfering with insect resistance and controlling symbiotic bacteria can be important steps for the successful application of microbial biopesticides.

ITRAQ-Based Comparative Proteomic Analysis of Larval Midgut From the Beet Armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) Challenged With the Entomopathogenic Bacteria Serratia marcescens.

Entomopathogenic bacteria Serratia marcescens is widely used as an environmentally friendly biocontrol agent against various pests, including Spodoptera exigua. Understanding the immune defense mechanism of S. exigua through comparative proteomic analysis can identify the key proteins expressed in response to the microbial infection. Here, we employed the as isobaric tags for relative and absolute quantification (iTRAQ) technique to investigate the effects of S. marcescens on the proteomic expression of S. exigua. Based on the molecular functional analysis, the differentially expressed proteins (DEPs) were mainly involved in the binding process and catalytic activities. Further bioinformatics analysis revealed important DEPs that played a crucial role in innate immunity of S. exigua with recognition (C-type lectin), melanization (propanol oxidase 3, serine protease, Serine-type carboxypeptidase activity, clip domain serine protease 4), antimicrobial activity (lysozyme, lysozyme-like, gloverin, cecropin B), detoxification (acetyl-CoA C-acetyltransferase, 3-dehydroecdysone 3-alpha-reductase, glucuronosyltransferase, glutathione S-transferase) and others. The Quantitative real-time PCR (qRT-PCR) results further indicated the significant upregulation of the immune-related genes in Spodoptera exigua following S. marcescens infection. To the best of our knowledge, this is the first iTRAQ based study to characterize S. marcescens mediated proteomic changes in S. exigua and identified important immune-related DEPs. The results of this study will provide an essential resource for understanding the host-pathogen interactions and the development of novel microbial biopesticides against various pests.

Microbial biopesticides in agroecosystems

Microbial biopesticides include several microorganisms like bacteria, fungi, baculoviruses, and nematode-associated bacteria acting against invertebrate pests in agro-ecosystems. The biopesticide sector is experiencing a significant growth and many discoveries are being developed into new biopesticidal products that are fueling a growing global market offer. Following a few decades of successful use of the entomopathogenic bacterium Bacillus thuringiensis and a few other microbial species, recent academic and industrial efforts have led to the discovery of new microbial species and strains, and of their specific toxins and virulence factors. Many of these have, therefore, been developed into commercial products. Bacterial entomopathogens include several Bacillaceae, Serratia, Pseudomonas, Yersinia, Burkholderia, Chromobacterium, Streptomyces, and Saccharopolyspora species, while fungi comprise different strains of Beauveria bassiana, B. brongniartii, Metarhizium anisopliae, Verticillium, Lecanicillium, Hirsutella, Paecilomyces, and Isaria species. Baculoviruses are species-specific and refer to niche products active against chewing insects, especially Lepidopteran caterpillars. Entomopathogenic nematodes (EPNs) mainly include species in the genera Heterorhabditis and Steinernema associated with mutualistic symbiotic bacteria belonging to the genera Photorhabdus and Xenorhabdus. An updated representation of the current knowledge on microbial biopesticides and of the availability of active substances that can be used in integrated pest management programs in agro-ecosystems is reported her.

Biological control of Monacha cartusiana “glassy clover land snails” by microbial biopesticides Biozed and Biogard, using bait technique

Abstract The effectiveness of microbial derived insecticides (Biozed and Biogard) were tested for controlling the subversive clover snails causing wastage of economic plants at Sharkia Governorate, Egypt, using poisonous baits technique. The toxicity index, LC50 and relative potency values reveals the potential activity of Biozed (fungal) than Biogard (bacterial) against M. cartusiana snails. Biogard caused no mortalities among treated clover snails at all at the first day of exposure. Mortality percentages appeared after one week and increased gradually with increasing concentrations and time of treatments. The highest concentrations of Biozed (0.75%) and Biogard (3.9%) caused 66.6% and 40% mortalities respectively after 28 days of exposure. From the biochemical parameters, an increment of total proteins, AST, ALT, α-esterase levels while a strong reduction on the total lipids, β-esterase and Phenoloxidase levels were observed after treatments with LC25 of biocides for three weeks. Histopathological investigations on the digestive and hermaphrodite glands revealed that sublethal concentration of Biozed produced tubular disruptions, vacuolation, excessive luminal secretions in digestive gland tissues. Malformed sperms and oocytes were spotted in ovotestis acini treated with Biozed. Biogard caused extensive luminal secretions, hemocytes infiltration and lysis of peripheral cells of digestive tubules while hermaphroditic acini showed disrupted sperms and oocytes.

Managing Fusarium oxysporum f. sp. vasinfectum Race 4 with beneficial microorganisms including entomopathogenic fungi

Fusarium spp. are dangerous pathogens of several commercially important crops around the world. Among non-chemical alternatives, beneficial microorganisms offer a potential control option for Fusarium and other soilborne pathogens. A greenhouse study was conducted using cotton as a model plant and F. oxysporum f. sp. vasinfectum Race 4 (FOV Race 4) as the pathogen to evaluate the efficacy of commercial formulations of microbial and botanical biopesticides. Streptomyces lydicus (Actinovate® AG), Bacillus amyloliquefaciens (Stargus®), giant knotweed extract (Regalia®), entomopathogenic fungi - Beauveria bassiana (BotaniGard® ES), Isaria fumosorosea (PFR-97™ 20% WDG), and Metarhizium brunneum (M. anisopliae; Met52® EC) were applied to FOV Race 4 infested soil in three treatment regimens, and the growth of susceptible Pima cotton seedling growth and health was monitored for 5 weeks. Treatments were generally effective against antagonizing FOV Race 4 especially when applied multiple times at a lower rate or once at a higher rate. Entomopathogenic fungi were as effective as other products that are exclusively used for disease management. Beauveria bassiana provided superior control for a long period compared to other treatments. This study reports the efficacy of non-chemical alternatives against FOV Race 4 and the potential of using entomopathogenic fungi for disease management in addition to their normal role of arthropod pest management.

Microbial Bio-Pesticides and Their Use in Integrated Pest Management

Crop pest management in agriculture is important to safeguard crop yield and increase productivity. The need for sustainable and eco-friendly pest management practices is strongly felt with the increasing awareness of the harmful effects of the synthetic insecticides on the non- target organisms, humans and the environment. The demand for bio-pesticides is rising steadily in all parts of the world. Therefore, the current study was carried out with the objectives to review, note and have the know-how all about microbial bio-pesticides and their use in pest management program. When used in integrated pest management systems, bio-pesticides efficacy can be equal to or better than conventional products, especially for crops like fruits, vegetables, nuts and flowers. Microbial bio-pesticides can be smart inputs and components in integrated pest management program. By combining performance and safety, they perform efficaciously while providing the flexibility of minimum application restrictions, superior residue and resistance management potential, and human and environmental safety benefits. It is very likely that in future their role will be more significant in agriculture and forestry. Bio-pesticides clearly have a potential role to play in development of future integrated pest management strategies hopefully, more rational approach will be gradually adopted towards bio-pesticides including microbial bio-pesticides in the near future and short-term profits from chemical pesticides will not determine the fate of bio-pesticides.

Improving energy efficiency of Bacillus velezensis broth microfiltration in tubular ceramic membrane by air sparging and turbulence promoter

AbstractBACKGROUNDPopularity of biocontrol has increased due to the growing environmental concerns and the demand for organic products. It is considered as a sustainable practice for efficient agricultural production. Microbial biopesticides offer environment‐friendly biotechnological alternative to chemical control of plant diseases and pests. Due to its advantages in cell separation cross‐flow microfiltration has emerged as a powerful alternative to the conventional separation methods. However, the flux enhancement remains to be addressed. This study has estimated the use of flux improvement techniques for biomass harvesting by microfiltration using tubular ceramic membranes. Investigated methods for flux enhancement were turbulence promoter, i.e. Kenics static mixer, two‐phase flow (air sparging) and the combination of these two methods.RESULTSSignificant flux improvement coincides with a reduction in specific energy consumption, while at the same time Bacillus velezensis cells have retained viability and antibacterial activity. The highest values of flux and corresponding improvement, compared to the microfiltration without enhancement techniques, are obtained in the case of combining Kenics static mixer and two‐phase flow (133.4 L m−2 h−1 and 502%). Flux improvement for air sparging was 134%, for turbulence promoter alone flux increase was 434%.CONCLUSIONThe methods proposed herein have achieved effective flux enhancement for cell harvesting. The obtained results also suggest encouraging basis to promote large‐scale economical production of biomass for biocontrol application. © 2019 Society of Chemical Industry

A Bacillus thuringiensis kurstaki Biopesticide Does Not Reduce Hatching Success or Tadpole Survival at Environmentally Relevant Concentrations in Southern Leopard Frogs (Lithobates sphenocephalus).

Amphibians are in global decline, and anthropogenic activities are known leading causes of their demise. Thus the interaction between agriculture and amphibian health has been examined for decades. Many facets of amphibian physiology and ecology place them at high risk among the nontarget organisms affected by agricultural byproducts. Research has shown that many chemicals and fertilizers affect amphibian growth, reproduction, and survival. The impacts differ based on the type of agricultural byproduct (e.g., chemical pesticide or nutrient-heavy fertilizer) and amphibian species, but the effects are usually negative. However, minimal research exists on how organic biopesticides interact with amphibian populations. Biopesticides utilize insecticidal bacteria as the active ingredient in lieu of synthetic chemicals. The inert ingredients present in biopesticide commercial products are considered safe to nontarget organisms. The present study tested the impacts of a commercial biopesticide on the survival of amphibian embryos and larvae. We found that expected environmental concentrations of the microbial biopesticide Monterrey B.t. did not significantly reduce survival in embryos or larvae. However, the higher doses used to assess threshold toxicity levels caused significant mortality. Our data suggest that biopesticides are not directly harmful to amphibian embryos or larvae in concentrations regularly applied for pest control. Environ Toxicol Chem 2019;39:155-161. © 2019 SETAC.

Novel combination of a biosurfactant with entomopathogenic fungi enhances efficacy against Bemisia whitefly.

Microbial surfactants are multifunctional surface-active molecules that have been overlooked in formulating microbial biopesticides. We report a novel approach using the biosurfactant rhamnolipid (RML) against the destructive cosmopolitan insect pest Bemisia tabaci, as well as the combined action of RML with aerial conidia of two entomopathogenic fungi, Cordyceps javanica and Beauveria bassiana. RML was also tested as a suspension agent to improve the recovery rate of conidia from solid substrate for fungal preparations. The recovery rate of conidia increased dramatically (two to five times) with RML compared with a standard surfactant (Tween 80). Spraying solutions of 0.075% and 0.1% (w/v) RML on B. tabaci third instar nymphs induced 100% mortality within 4days. Conidial suspensions at 5 × 106 conidia/mL amended with RML at 0.01% or 0.05% markedly increased nymphal mortalities and considerably reduced LC50 . Conidial suspensions of B. bassiana with 0.05% RML added were more effective against whitefly nymphs (87.3% mortality) than C. javanica + RML (51.4% mortality). Our results show that this bacterium-based RML improved the recovery rate of hydrophobic conidia, and that mixtures of RML with fungal spore suspensions increased their insecticidal activity. © 2019 Society of Chemical Industry.