Biological Control Research Articles

Mechanisms of Biocontrolling Action of Yeasts in Post-Harvest Fruit: A Review

Objective: The aim of the research is to address the biological control developed by yeasts in the post-harvest of fruits, based on a brief literature review on the subject. Theoretical Framework: The use of chemical control mechanisms and biocontrol is based on the increasing need for sustainable agricultural practices that ensure human health and environmental preservation. While synthetic fungicides are effective in combating fungal diseases, their excessive use raises concerns about pathogen resistance and public health risks. In this context, the development of biocontrol agents, such as yeasts, emerges as a viable and ecological alternative, promoting food safety and crop protection with a lower environmental impact. Method: A narrative literature review was conducted using major scientific databases to collect articles on the biological control of yeasts in the post-harvest of fruits. Key studies were evaluated to measure effectiveness and understand the mechanisms related to the biocontrol action of these yeasts. Results and Discussion: The predominant chemical control for fungal diseases is being replaced by sustainable alternatives, such as yeast-based biofungicides, which demonstrate effectiveness against pathogens in post-harvest settings. Mechanisms such as killer activity and the production of hydrolytic enzymes stand out in biocontrol. Although promising, further research is needed to deepen the understanding of biocontrol agents and their applications.

Biocontrol Efficacy of Trichoderma and Bacillus Isolates against Sclerotium rolfsii under in vitro Conditions

Background: Sclerotium rolfsii is a polyphagous pathogen which is uneconomical and difficult to control due to its broad host range and persistence due to its tough resting structures, i.e., sclerotia. Chemical control has been supplanted by biological phytopathogen control. Antibiotic microorganisms are regarded as one of the viable management techniques in an integrated approach for ecofriendly management. Methods: Twenty three Trichoderma spp. and twenty one Bacillus species were isolated at Groundnut Pathology Laboratory, ICRISAT, Patancheru from rhizospheric soils of Telangana during rabi 2022-23 and 2023-24 and examined for antagonistic activity against Sclerotium rolfsii in an effort to design an effective biocontrol system for the management of Sclerotium rolfsii in groundnut. Result: The highest antagonistic activity against Sclerotium rolfsii has been observed in Trichoderma viride and Bacillus cereus. In the dual culture assay, Trichoderma viride and Bacillus cereus inhibited Sclerotium rolfsii by up to 65.33 per cent and 58.22 per cent, respectively. In the metabolites assay, Trichoderma viride and Bacillus cereus inhibited Sclerotium rolfsii by 63.33 per cent and 55.40 per cent, respectively. Thus, Trichoderma viride and Bacillus cereus displayed promising biofungicidal capabilities against the stem rot pathogen. ​

Pioneering Innovations in Biological Weed Control: A Comprehensive Review

The biological method of weed control is an effective option. Before implementing bio-agents, there is a need for a better understanding of the mechanisms involved in interactions by multiple agents against weeds. This covers knowledge of how plants integrate and prioritize their responses to multiple attackers. Across the globe, terrestrial ecosystems are known to be characterized by a huge diversity of species and a corresponding diversity of interactions between these species. These include species of different trophic levels of habitats on the same food chain. Plants undoubtedly play significant role as intermediaries in interactions between the insect and microbial populations with which they are involved. Plant interactions brought forth by one species can have cascading impacts on other species, influencing their abundances and the composition of communities. Several research efforts are underway to develop highly effective biological control agents to reliably control a problematic broad spectrum of weeds. Sustainable and ecosystem-compatible weed management for controlling weeds by biological means, such as insects, bio-agents, myco-herbicides and harmful Rhizobacteria. Their interaction with cultural practices and allelochemicals are some biological components of sustainable agriculture. Hence, biological agents enhance efficiency and restrict the detrimental effect of weeds compared to weeds being left alone. The challenge is to identify appropriate microbe/bioagents, which reduce weed growth. Logically, biological weed management is the only way to control weeds in eco-friendly weed management.

Morphological and molecular characterization of Purpureocillium lilacinum along with its biopesticidal effect against fall armyworm (Spodoptera frugiperda) in Southern Taiwan

Abstract Background Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), a key agricultural pest, impacts a broad spectrum of crop species, such as cotton, maize, rice, sorghum, and a range of vegetables. Chemical pesticides and transgenic maize are commonly used to protect crops against this major pest. However, biological control offers a safer and more sustainable solution for long-term FAW management. Entomopathogenic fungi (EPF), a substitute for synthetic insecticides, have been proven to be an effective biocontrol agent for managing pest populations. The present study objective is to isolate and identify the EPF, Purpureocillium lilacinum from soil using morphological and molecular techniques and evaluate its pathogenicity against FAW eggs and various larval stages under different spore concentrations. Results The micro-morphological characteristics fluctuated in growth behavior, appearance, and color under diverse growth media and temperatures. Molecular analysis, which involved constructing a phylogenetic tree from ITS and TEF gene regions, confirmed that PT-02 was P. lilacinum. The pathogenicity of the fungus was tested on FAW eggs, neonates, and larvae at multiple concentrations (1 × 108, 1 × 107, and 1 × 106 spores/ml), resulting in variation mortality. The egg mortality rate at 1 × 108, 1 × 107, and 1 × 106 spores/ml was 98, 98 and 96%, respectively. The neonate mortality rate was 100%, while first and second instars larvae mortality ranged from 10–36% across three concentrations, seven days after treatment (DAT). The median lethal concentration (LC50) values of P. lilacinum PT-02 against FAW eggs, first and second instars, were 3.02 × 107, 1.38 × 108, and 2.56 × 108 spore/ml, respectively. Conclusions The findings revealed that the native strain of P. lilacinum exhibited strong virulence against FAW, suggesting its potential use as an effective biocontrol agent for managing field pest populations.

Understanding the Pathogenesis, Biocontrol Mechanisms, and Factors Influencing Biocontrol Effectiveness for Soil-Borne Diseases in Panax Plants

Panax plants are known for their significant medicinal and economic value. Being perennial, they are prone to soil-borne diseases during cultivation. However, there has been limited research on the pathogenesis of soil-borne diseases and the diversity of pathogens. While biological control has gained attention for its efficacy and environmental benefits, the factors affecting its efficiency still need thorough evaluation. This review summarizes the influence of biotic factors, such as pathogens and hosts, and environmental factors on the occurrence of soil-borne diseases and pathogen diversity. Additionally, we synthesized bacterial, actinobacterial, and fungal diversity for the biocontrol of soil-borne diseases and their functional mechanisms. Moreover, the review delves into the factors influencing the efficacy of biocontrol, including microbial species, the inoculation method and inoculation volume, and inoculant composition. This article serves as a valuable resource for enhancing the efficiency of biological control and optimizing strategies for managing soil-borne diseases in Panax cultivation in the future.

Characterization of a plant‐pathogenic T3SS‐lacking Xanthomonas strain isolated from common ragweed

AbstractCommon ragweed (Ambrosia artemisiifolia) is one of the leading causes of allergenic rhinitis, as well as a major weed of many crops. Biological control with plant pathogens, such as fungi and bacteria, represents an attractive alternative to the application of synthetic herbicides to control this noxious weed. In this study, we isolated a Xanthomonas strain (designated as 10‐10) from a diseased common ragweed plant collected in southern Quebec, Canada. We characterized the bioherbicidal potential of this strain against common ragweed, and determined whether it can infect other plant species. Its genome was sequenced using PacBio's SMRT technology, enabling us to gain insight into the phylogenetic placement of this strain within the genus Xanthomonas, and to study the repertoire of virulence‐associated genes and clusters. Xanthomonas sp. 10‐10 belongs to a clearly defined subclade within clade C (group 2), which includes X. vesicatoria, X. dyei and X. pisi. While this strain is closely related to X. pisi, it represents a new species within the genus Xanthomonas. Surprisingly, this strain lacks a type III secretion system, which is the main virulence determinant in pathogenic Xanthomonas spp., but harbours an arsenal of cell wall‐degrading enzymes. The addition of the organosilicone surfactant Silwet L‐77 drastically increased the disease symptoms caused by Xanthomonas sp. 10‐10 on common ragweed plants grown under controlled conditions, but the plants remained alive. This strain also caused disease symptoms on tomato, pepper and lettuce. More research is needed to develop Xanthomonas‐based bioherbicide specifically targeting common ragweed.

Using ecological niches to determine potential habitat suitability for Psacothea hilaris (Coleoptera: Cerambycidae) and its natural enemies in China under future climates.

Climate change impacts the distribution of pests and its natural enemies, prompting this study to investigate the dynamics and shifts in distribution under current and future climate conditions. The spatial pattern of Psacothea hilaris (Pascoe) (Coleoptera: Cerambycidae) in China was analyzed, and the MaxEnt model was optimized to predict the potential geographic distribution of P. hilaris and its two natural enemies (Dastarcus helophoroides (Fairmaire) (Coleoptera: Bothrideridae) and Dendrocopos major (Linnaeus) (Piciformes: Picidae)) in China, to further analyze the key environmental factors affecting the survival of P. hilaris and its natural enemies, and to determine the potential of using D. helophoroides and D. major as natural enemies to control P. hilaris. The results showed that the suitable ranges of P. hilaris and natural enemies are expanding under the influence of climate change, and both have migrated to higher latitudes. The potential ranges of D. helophoroides, D. major, and P. hilaris are highly similar. It is noteworthy that the potential range of D. helophoroides completely covers the potential range of P. hilaris. This indicates that D. helophoroides and D. major can be employed as biological control agents to manage P. hilaris populations. This study provides a theoretical framework and empirical evidence for the development of early warning and green control strategies for P. hilaris.

Soil nematode communities differ across long-term land-use intensities in relation to soil physical, chemical, and biological parameters

Soil disturbance, reduced crop diversity, and decreased residue in intensively managed systems can negatively impact soil biological communities and soil health. This study examined the impact of long-term (>20 years) low- (forest, grassland), medium- (diversified annual cropping), and high-intensity (annual cropping, frequently to potatoes) land-use on soil nematode communities and soil health in 59 sites across Prince Edward Island, Canada. Soil samples (0–15 cm) were collected at five locations per site and analysed for soil biological (nematode communities, respiration, soil organic matter, permanganate oxidizable carbon (POXc), soil protein), chemical (pH, N, soil N supply, extractable nutrients), and physical (bulk density, texture) properties. Soil pH and extractable nutrients were lowest in the low-intensity sites, while total C and C:N ratios were highest and decreased with increasing land-use intensity (low > medium > high). Soil respiration, POXc, and protein were lowest for high-intensity sites. Low-intensity sites had greater nematode Shannon diversity and richness, and higher maturity and structure indices than the medium- and high-intensity sites ( p < 0.05), signifying a more structured nematode community. Nematode communities from the high-intensity sites were more degraded and had significantly higher basal indices compared to the low- and medium-intensity sites. At the trophic level, the low-intensity system had higher numbers of omnivores and lower abundance of bacterivores. These differences in nematode trophic composition may result in differences in ecosystem function, including nutrient cycling and biological control.

Rising orthotospovirus incidence in India: Challenges and advances in management

Orthotospoviruses (OV) have emerged as a significant agricultural threat in India, posing a severe risk to critical crops, including tomato, chilli, watermelon and groundnut. This review explores the rising incidence of OV, including Groundnut Bud Necrosis Orthotospovirus (GBNV), Watermelon Bud Necrosis Orthotospovirus (WBNV), Capsicum Chlorosis Orthotospovirus (CaCV), Peanut Yellow Spot Orthotospovirus (PYSV), Iris yellow spot Orthotospovirus (IYSV) and Tomato Spotted Wilt Orthotospovirus (TSWV), along with the challenges in their management. These viruses have led to severe yield losses, sometimes causing complete crop failure due to their wide host range and the polyphagous nature of thrips. This further complicates control efforts by facilitating rapid spread across diverse crops and regions. The review highlights the multifaceted challenges in managing OV and thrips, including the lack of durable host resistance, limited diagnostic capabilities, and difficulties in controlling thrips populations. Current management strategies, including cultural practices, chemical control, biological control and resistant genotype development, have shown limited efficacy in providing long-term solutions. Recent advancements in biotechnological approaches, such as RNA interference, are discussed as promising pathways for improved virus management. The review underscores the need for genome editing techniques, such as CRISPR/Cas9, which offer the capacity to develop virus-resistant plants by targeting essential viral or vector genes to disrupt transmission cycles. Additionally, using nanoparticles for targeted delivery of antiviral compounds and novel detection tools presents another innovative solution to effectively mitigate the impact of OV on Indian agriculture.

PHENOMENON OF BACTERIAL RESISTANCE IN OIL PRODUCTION AND GATHERING SYSTEM

In this paper, the active substances of bactericides and the mechanisms of their action are considered. Information on the mechanism of bacterial adsorption to the metal surface, which forms the most corrosive form of bacterial colonies – the adhered one – is presented. Methods of biological contamination control, both physical and chemical, are also considered. The mechanism of bactericidal action of chemical compositions consisting of 3 stages (interaction with water, interaction of bactericide aqueous solutions with bacterial cell membranes, interaction of bactericide with cytoplasmic membrane) is also reviewed. The main types of bacterial resistance common in water circulation systems, reservoir pressure maintenance systems, oil production, transportation, gathering and storage systems are summarized. The mechanisms of occurrence of each type of manifestation and method of spreading resistance between colonies are considered. It is important to note that at the moment, methods to control each of the cases of resistance when using bactericides in oil production have been poorly studied, while constant and non-alternating dosing of reagents leads to bacteria mutation and a decrease in the effectiveness of bactericidal action, which, in turn, leads to significant technological problems and economic costs. Therefore, an important step in choosing bactericides, types and methods of treating an infected environment is to study bacterial resistance. The article accumulates and summarizes information on the methods currently used to prevent bacterial resistance.

Isolation and Evaluation of Indigenous Isolates of Beauveria bassiana and Synergistic Control of Spodoptera frugiperda with the Parasitoid Microplitis prodeniae

Entomopathogenic fungi (EPFs) are capable of infecting a variety of insect pests and are widely used as biopesticides worldwide. This study intended to isolate indigenous EPFs from cadavers of Protaetia brevitarsis and investigate their effects on the fall armyworm Spodoptera frugiperda (FAW), a globally widespread invasive pest. Morphological and molecular analyses confirmed four native EPF strains all belong to Beauveria bassiana. Pathogenicity tests showed they were virulent toward FAW 1st instar larvae. The application of EPFs either by dipping or spraying significantly increased the larval mortalities compared to the control group, with corrected mortalities ranging from 92% to 73% after dipping in a fungal suspension of 108 conidia/mL, and those ranging from 76% to 35% after spraying with a fungal suspension of 107 conidia/mL. Our findings revealed the infectivity of four strains to FAW larvae significantly changed in a dose- and time-dependent manner. In addition, the combination use of the local B. bassiana strain and parasitoid Microplitis prodeniae resulted in a significantly enhanced S. frugiperda 3rd instar larval mortality compared to a single inoculation with one of them, suggesting an apparent synergistic effect for the joint application of these two biological control agents. The mortality inflicted by B. bassiana was probably promoted by the release of parasitoids, since the parasitoids’ movements and attacks could strengthen the fungal distribution and infection processes. This study underscores the potential of the combination use of EPFs and parasitoids against S. frugiperda early-instar larvae, and provides insights into the consequences of integrating these EPFs into integrated pest management systems.

Virome of red imported fire ants by metagenomic analysis in Guangdong, southern China

The red imported fire ant (RIFA) has made China its habitat for approximately 25 years, but few reports have described the species and amount of virus circulating in it. Researchers are currently exploring viruses associated with RIFAs as potential biological control agents against invasive ants. The present meta-transcriptome analysis revealed the virome of red imported fire ants in Guangdong, southern China, which included 17 viruses, including Solenopsis invicta virus 4-GD (SINV-4) and Guangdong Polycipiviridae ant virus 1 (GPAV1) in the Polycipiviridae family; Solenopsis invicta virus 1-GD (SINV-1), and Guangdong Dicistroviridae ant virus 2-3 (GDAV2-3) in the Dicistroviridae family; Guangdong Iflaviridae ant virus 4-9 (GIAV4-9) in the Iflaviridae family; Guangdong Parvoviridae ant virus 10 (GPAV10) in the Parvoviridae family; and Guangdong ant virus 11-15 (GAV11-15). A total of 15 novel viruses and 2 known viruses were identified in this study. These findings reveal the virome of red imported fire ants in Guangdong Province and present a different result from that of a similar study reported in the United States, providing more choices for potential classical biological control agents against red imported fire ants in China.

Pleiotropic effects of Ebony on pigmentation and development in the Asian multi-coloured ladybird beetle, Harmonia axyridis (Coleoptera: Coccinellidae).

Melanin plays a pivotal role in insect body pigmentation, significantly contributing to their adaptation to diverse biotic and abiotic environmental challenges. Several genes involved in insect melanin synthesis showed pleiotropic effects on insect development and reproduction. Among these, the N-β-alanyl dopamine synthetase gene (Ebony) is integral to the pigmentation process. However, the full spectrum of its pleiotropic impacts is not yet thoroughly understood. In this study, we identified and characterised the HaEbony gene in the Asian multi-coloured ladybird beetle (Harmonia axyridis) and found that HaEbony gene is a conserved gene within the Coleoptera order. We aimed to further explore the multiple roles of HaEbony in the physiology and behaviour in H. axyridis. The CRISPR/Cas9 system was applied to generate multiple HaEbony knockout allele (HaEbony+/-), showing nucleotide deletion in the G0 and G1 generations. Remarkably, the resultant HaEbony+/- mutants consistently displayed darker pigmentation than their wild-type counterparts across larval, pupal and adult stages. Furthermore, these HaEbony+/- individuals (G0) demonstrated an enhanced predatory efficiency, evidenced by a higher number of aphids consumed compared to the wild type. A significant finding was the reduced egg hatchability in both G0 and G1 generations of the HaEbony+/- group, highlighting a potential reproductive fitness cost associated with HaEbony deficiency. In conclusion, our study not only sheds light on the multifaceted roles of HaEbony in H. axyridis but also highlights the potential of employing CRISPR/Cas9-targeted modifications of the Ebony gene. Such genetic interventions could enhance the environmental adaptability and predatory efficacy of ladybirds, presenting a novel strategy in biological control application.

Biocontrol Potential of a Native Trichoderma Collection Against Fusarium oxysporum f. sp. cubense Subtropical Race 4

The Canary Islands lead banana (Musa acuminata) production in the EU. Different fungal pathogens affect this crop in subtropical areas, with Fusarium oxysporum f. sp. cubense subtropical race 4 (Foc-STR4) being the most important in the Canary Islands. With the aim of developing environmentally sustainable techniques for disease control, this study presents the results of the evaluation of the antifungal capacity of a native Trichoderma collection (12 species, 109 isolates) obtained from banana soils. The results demonstrate the diversity of biocontrol genes and the in vitro antagonistic potential of different native Trichoderma species/isolates against two Foc-STR4 strains obtained from plants with Panama disease symptoms. Trichoderma virens (TF18), a dominant species in banana soils in the Canary Islands, showed a high capacity to inhibit the growth of Foc-STR4 in different in vitro assays. Trichoderma atrobrunneum (TF01) showed mycoparasitism capacity through the spiral coil around the hyphae of the pathogen. In addition, the genome analysis of T. atrobrunneum (TF03) showed 69 putative biosynthetic gene clusters, with the notable presence of the trichothecene tri5 gene. Finally, our work demonstrates that the soils of the Canary Islands banana crops are a potential source of environmentally adapted biological control agents to control or reduce the incidence of Foc-STR4.

A Brief Review of the Microweiseinae (Coleoptera: Coccinellidae) of the Indian Region, Including Description of a New Species

Indian species of Microweiseinae are reviewed, comprising eight species (five species of Serangium Blackburn, one species of Microserangium Miyatake, and two species of Scymnomorphus Weise, including one new species from the southern Indian state of Kerala, Scymnomorphus ochraceus sp. n.). Illustrated diagnostic accounts are given for all species with details of distribution, biology, and host insects, wherever they are known. Immature stages are illustrated for Serangium parcesetosum Sicard and Serangium chapini (Kapur). An updated checklist of the Microweiseinae of India is given. The need for focused collections and systematic studies to unearth the hidden diversity of Indian Microweiseinae is discussed, and comments on their poor utilization in applied biological control in India are made.

Metabolomics reveals altered biochemical phenotype of an invasive plant with potential to impair its biocontrol agent’s establishment and effectiveness

A plausible, but largely unexplored reason for many weed biocontrol agents failing to establish or being ineffective, could involve abiotically induced changes to an invasive plants’ biochemical phenotype and consequent enhanced herbivore resistance. Considerable literature demonstrates that chemically altered plant phenotypes can impair insect life history performance. Heather beetle, (Lochmaea suturalis), introduced to control invasive heather (Calluna vulgaris) in New Zealand (NZ) was difficult to establish and displays variable effectiveness. Using UHPLC-MS non-targeted metabolomics, we analysed primary and secondary metabolites of C. vulgaris from its native range (Scotland) and it’s introduced range (NZ), between which, differences in soil nutrients and ultraviolet light exist. We also explored secondary metabolite variation between sites within each range. New Zealand samples had the highest number of amplified metabolites, most notably defensive phenylpropanoids, supporting the concept of abiotically induced upregulation of key biosynthetic pathways. Analysis of secondary metabolite variation within each range revealed differences between sites but found little correlation of phenylpropanoid levels being influenced by variable soil nutrients. These results validate questions about the possibility of abiotically altered biochemical phenotypes in invasive plants, influencing weed biocontrol agent establishment and effectiveness, and show the potential for metabolomics in assisting future, or retrospectively analysing biological control programmes.

Biocontrol Agents Inhibit Banana Fusarium Wilt and Alter the Rooted Soil Bacterial Community in the Field

Banana is an important fruit and food crop in tropical and subtropical regions worldwide. Banana production is seriously threatened by Fusarium wilt of banana (FWB), a disease caused by Fusarium oxysporum f. sp. cubense, and biological control is an important means of curbing this soil-borne disease. To reveal the effects of biocontrol agents on inhibiting FWB and altering the soil bacterial community under natural ecosystems, we conducted experiments at a banana plantation. The control efficiency of a compound microbial agent (CM), Paenibacillus polymyxa (PP), Trichoderma harzianum (TH), and carbendazim (CA) on this disease were compared in the field. Meanwhile, the alterations in structure and function of the rooted soil bacterial community in different treatments during the vigorous growth and fruit development stages of banana were analyzed by microbiomics method. The results confirmed that the different biocontrol agents could effectively control FWB. In particular, CM significantly reduced the incidence of the disease and showed a field control efficiency of 60.53%. In terms of bacterial community, there were no significant differences in the richness and diversity of banana rooted soil bacteria among the different treatments at either growth stage, but their relative abundances differed substantially. CM treatment significantly increased the ratios of Bacillus, Bryobacter, Pseudomonas, Jatrophihabitans, Hathewaya, and Chujaibacter in the vigorous growth stage and Jatrophihabitans, Occallatibacter, Cupriavidus, and 1921-3 in the fruit development stage. Furthermore, bacterial community function in the banana rooted soil was affected differently by the various biocontrol agents. CM application increased the relative abundance of multiple soil bacterial functions, including carbohydrate metabolism, xenobiotic biodegradation and metabolism, terpenoid and polyketide metabolism, lipid metabolism, and metabolism of other amino acids. In summary, our results suggest that the tested biocontrol agents can effectively inhibit the occurrence of banana Fusarium wilt and alter the soil bacterial community in the field. They mainly modified the relative abundance of bacterial taxa and the metabolic functions rather than the richness and diversity. These findings provide a scientific basis for the use of biocontrol agents to control banana Fusarium wilt under field conditions, which serves as a reference for the study of the soil microbiological mechanisms of other biocontrol agents.

In vitro evaluation of the pathogenicity of fungi isolated from the Urabá region (Antioquia, Colombia) against Aedes aegypti larvae

Introduction. Aedes aegypti is an important vector of arboviral diseases like dengue among others. Traditional control strategies, such as the use of insecticides, have lost effectiveness due to the emergence of resistance in mosquito populations. Biological control and fungi applied for biocontrol are presented as viable and ecological alternatives. Objective. To evaluate in vitro pathogenicity of Trichoderma sp. isolates obtained from Urabá (Antioquia) on larvae of Ae. aegypti, and to determine the mean lethal concentration and mean lethal time of the most pathogenic isolate. Materials and methods. Using the sentinel larvae method of Ae. aegypti, fungi were isolated from water bodies in the Urabá region (Antioquia). The isolates were characterized morphologically and molecularly to determine their taxonomic identity. Pathogenicity tests were performed in vitro on Ae. aegypti larvae in the L2/L3 stages. Subsequently, a strain was selected to establish its mean lethal concentration and mean lethal time. Results. Trichoderma sp. strain AP-91 caused high mortality in larval populations of Ae. aegypti. We estimated a mean lethal concentration of 1.8 × 107 conidia/ml and a mean lethal time of 20.67 hours. Conclusion. The strain AP-91 showed potential for its use as biological control of Ae. aegypti, making it a suitable candidate for scale-up cultures applied to integrated vector management. This research suggests exploring compounds and enzymes produced by the AP-91 strain to understand better its pathogenicity.

Antibacterial, Herbicidal, and Plant Growth-Promoting Properties of Streptomyces sp. STD57 from the Rhizosphere of Adenophora stricta

Bacterial wilt triggered by the soil-borne pathogenic bacterium Ralstonia solanacearum is one of the most serious diseases in tomato plants, leading to huge economic losses worldwide. Biological control is considered an environmentally friendly and sustainable way to manage soil-borne diseases. In this study, Streptomyces sp. STD57 isolated from the rhizosphere of Adenophora stricta showed strong antibacterial activity against R. solanacearum. Pot experiments showed that strain STD57 exhibited a significant biocontrol effect (81.7%) on tomato bacterial wilt in the greenhouse environment. Furthermore, strain STD57 could inhibit the growth of weeds (Amaranthus retroflexus, Portulaca oleracea, and Echinochloa crusgalli) but promote the growth of crops (wheat, rice, and tomato). The plant growth-promoting substance was identified as indoleacetic acid (IAA) by high-pressure liquid chromatography–mass spectrometry and genome analysis. Coarse separation of the fermented extracts revealed that the antibacterial and herbicidal substances were mainly in the fermentation supernatant and belonged to different products. These findings suggested that strain STD57 may be a potential biocontrol and bioherbicide agent useful in agriculture.

Benefits of Crotalaria juncea L. as Green Manure in Fertility and Soil Microorganisms on the Peruvian Coast

The soils of the Barranca valley are among the best soils in Peru, but with so many years of application of agrochemicals and other agricultural practices, they are losing their productive capacity. Consequently, it was suggested to assess the impact of Crotalaria juncea L. as a green manure on soil fertility and the populations of bacteria and fungi present in the soil. Crotalaria was cultivated for 75 days and incorporated as green manure. After 90 days, the presence of bacteria and fungi was evaluated. Metabarcoding was employed, and the 16S rRNA and ITS2 amplicons were sequenced using the Illumina MiSeq platform. The sequences were processed using various bioinformatics tools. The results indicate that soils have a high diversity of bacteria and fungi. Likewise, in plots where the presence and action of natural biocontrol is suppressed (C0 and P0), pathogenic fungi increase their population in the fallow period (C1), while in P1, the addition of Crotalaria as a green manure promotes an increase in the population of bacteria and fungi, and at the same time it suppresses pathogenic fungi. The genera (bacterial and/or fungal) that increase due to the effect of Crotalaria are beneficial because they are involved as degraders of organic matter, promotion of plant growth and biological control of pathogens. Crotalaria is an alternative to improve soil fertility, increase the beneficial bacterial population, and reduce pathogenic fungi.