First record of Aspergillus oryzae as an entomopathogenic fungus against the poultry red mite Dermanyssus gallinae

Entomopathogenic fungi in crops protection with an emphasis on bioactive metabolites and biological activities

Plant pathogens with their abundance are harmful and cause huge damage to different agricultural crops and economy of a country as well as lead towards the shortage of food for humans. For their management, the utilization of entomopathogenic fungi is an eco-friendly technique, sustainable to the environment, safe for humans and has promising effect over chemical-based pesticides. This process requires a biochemical mechanism, including the production of enzymes, toxins, and other metabolites that facilitate host infection and invasion. Essential enzymes such as chitinase, proteinase, and lipase play a direct role in breaking down the host cuticle, the primary barrier to EPF (Entomopathogenic Fungi) infection. Additionally, secondary metabolites such as destruxins in Metarhizium, beauvericin in Beauveria, hirsutellides in Hirsutella, isarolides in Isaria, cordyols in Cordyceps, and vertihemipterins in Verticillium, among others, act both directly and indirectly to disable the defense mechanisms of insect hosts, thereby accelerating the EPF infection process. The chemical composition of these secondary metabolites varies, ranging from simple non-peptide pigments such as oosporine to highly complex piperazine derivatives such as vertihemiptellides. The biocontrol efficacy of EPF is extensively studied, with numerous fungal strains commercially available on a large scale for managing arthropod pests. This review emphasizes the role of proteins and enzymes against crop pathogens, detailing their mode of action, and describing the metabolites from entomopathogenic fungi and their biological activities. In doing so, these findings contribute to establishing a symbiotic equilibrium between agricultural productivity and environmental conservation.

Acaricidal activity of bioactive compounds isolated from Aspergillus oryzae against poultry red mites, Dermanyssus gallinae (Acari: Dermanyssidae)

Dermanyssus gallinae, the poultry red mite (PRM), is an obligate ectoparasite feeding on poultry blood, seriously affecting the health of layers and egg production. The control of PRMs mainly relies on chemical drugs, which is facing several challenges such as the environment pollution and drug resistance. Using fungal metabolites is an environmentally friendly alternative for the control of pests. However, few studies have been conducted on the efficacy of fungal metabolites against D. gallinae. In this study, five strains of fungi were isolated from D. gallinae under laboratory conditions, and their extracts with ethyl acetate were tested for acaricidal activity on D. gallinae. The crude extract of Aspergillus oryzae caused 75.55 ± 6.94% mortality of mites at a concentration of 12.5 mg/mL, showing the highest acaricidal effect in all extracts. Subsequently, the extract of A. oryzae was isolated by bio-guided fractionation, and ten major compounds were identified by LC-MS/MS analysis. The results of bioassays indicated that five compounds exhibited acaricidal activity against D. gallinae. N, N-dimethyldecylamine N-oxide was the optimal acaricidal compound with LC₅₀ of 0.568 mg/mL. Additionally, palmitic acid, triethanolamine, cuminaldehyde, and 2,4-dimethylbenzaldehyde also showed acaricidal activity. These compounds have great application potential in the mite control, and the analysis of these fungal acaricidal substances provides a new idea and basis for the subsequent development of PRM control technology.

Characterization and transcriptomic analysis of a native fungal pathogen against the rice pest Nilaparvata lugens

The brown planthopper (BPH), Nilaparvata lugens, is one of the most destructive pests of rice. Given the threats posed by insecticide resistance to its control, eco-friendly strategies based on microbial pathogens emerged as a promising biocontrol alternative. In the present study, we isolated a native fungal pathogen against BPH from infected BPH cadavers and preliminarily identified as a strain of Aspergillus fumigatus based on morphological and molecular methods. Laboratory bioassay revealed that this fungal strain was highly virulent to BPH both at nymphal and adult stages, with the median lethal times (LT₅₀) of 7.5 and 5.8 days under high conidial concentration of 1 × 10⁹ conidia mL^-1. A genome-wide view of gene expressions in BPH against fungal attack was analyzed by transcriptomic sequencing and consequently a large number of differentially expressed genes that mainly involved in host immune defense and cell detoxification were found. RNAi-mediated knockdown of an upregulated gene encoding a serine protease (NlSPN) could cause a significant decrease in BPH survival. Combination of dsRNA injection and fungal infection showed an additive effect on BPH mortality, which provided clues to develop new pest management strategies against BPH.

Natural occurrence of fungal endophytes in cultivated cucumber plants in Syria, with emphasis on the entomopathogen Beauveria bassiana

A survey was conducted to investigate endophytic Beauveria spp. and associated fungi in the tissues of cucumber plants (Cucumis sativus L.) cultivated in open fields and greenhouses in some regions of Syria during 2018-2019. Cultures of fungal endophytes belonging to nine genera were obtained (frequency %): Aspergillus (87.1%), Penicillium (41.23%), Fusarium (38.15%), Beauveria (12.83%), Trichoderma (9.87%), Colletotrichum (4.36%), Cladosporium (3.54%), Alternaria (2.79%), and Chaetomium (2.2%). Only Beauveria and Trichoderma cultures were entomopathogenic. Beauveria bassiana isolates were identified morphologically and molecularly from the stems, leaves, petioles, and fruits of cucumber plants collected at seven agricultural sites. Their ability to artificially colonize all cucumber plant parts was confirmed in the laboratory using soil drench. In this study, the natural association between the endophytic entomopathogenic fungus B. bassiana and cucumber plants is newly reported. In addition, a checklist of plant species reported in the literature to harbor this fungus is also provided.

First Record of Aspergillus fijiensis as an Entomopathogenic Fungus against Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae)

The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) is the most widespread and devastating pest species in citrus orchards and is the natural vector of the phloem-limited bacterium that causes Huanglongbing (HLB) disease. Thus, reducing the population of D. citri is an important means to prevent the spread of HLB disease. Due to the long-term use of chemical control, biological control has become the most promising strategy. In this study, a novel highly pathogenic fungal strain was isolated from naturally infected cadavers of adult D. citri. The species was identified as Aspergillus fijiensis using morphological identification and phylogenetic analysis and assigned the strain name GDIZM-1. Tests to detect aflatoxin B1 demonstrated that A. fijiensis GDIZM-1 is a non-aflatoxin B1 producer. The pathogenicity of the strain against D. citri was determined under laboratory and greenhouse conditions. The results of the laboratory study indicated that nymphs from the 1st to 5th instar and adults of D. citri were infected by A. fijiensis GDIZM-1. The mortality of nymphs and adults of D. citri caused by infection with A. fijiensis increased with the concentration of the conidial suspension and exposure time, and the median lethal concentration (LC50) and median lethal time (LT50) values gradually decreased. The mortality of D. citri for all instars was higher than 70%, with high pathogenicity at the 7th day post treatment with 1 × 108 conidia/mL. The results of the greenhouse pathogenicity tests showed that the survival of D. citri adults was 3.33% on the 14th day post-treatment with 1 × 108 conidia/mL, which was significantly lower than that after treatment with the Metarhizium anisopliae GDIZMMa-3 strain and sterile water. The results of the present study revealed that the isolate of A. fijiensis GDIZM-1 was effective against D. citri and it provides a basis for the development of a new microbial pesticide against D. citri after validation of these results in the field.

Welfare issues and potential solutions for laying hens in free range and organic production systems: A review based on literature and interviews

In free-range and organic production systems, hens can make choices according to their needs and desires, which is in accordance with welfare definitions. Nonetheless, health and behavioral problems are also encountered in these systems. The aim of this article was to identify welfare challenges observed in these production systems in the EU and the most promising solutions to overcome these challenges. It is based on a review of published literature and research projects complemented by interviews with experts. We selected EU specific information for welfare problems, however, the selected literature regarding solutions is global. Free range use may increase the risk of infection by some bacteria, viruses and parasites. Preventive methods include avoiding contamination thanks to biosecurity measures and strengthening animals' natural defenses against these diseases which can be based on nutritional means with new diet components such as insect-derived products, probiotics and prebiotics. Phytotherapy and aromatherapy can be used as preventive and curative medicine and vaccines as alternatives to antibiotics and pesticides. Bone quality in pullets and hens prevents keel deviations and is favored by exercise in the outdoor range. Free range use also lead to higher exposure to variable weather conditions and predators, therefore shadow, fences and guard animals can be used to prevent heat stress and predation respectively. Granting a free range provides opportunities for the expression of many behaviors and yet many hens usually stay close to the house. Providing the birds with trees, shelters or attractive plants can increase range use. Small flock sizes, early experiences of enrichment and personality traits have also been found to enhance range use. Severe feather pecking can occur in free range production systems, although flocks using the outdoor area have better plumage than indoors. While many prevention strategies are facilitated in free range systems, the influence of genetics, prenatal and nutritional factors in free range hens still need to be investigated. This review provides information about practices that have been tested or still need to be explored and this information can be used by stakeholders and researchers to help them evaluate the applicability of these solutions for welfare improvement.

Evaluation of the in vitro acaricidal activity of ethanol extracts of seven Chinese medicinal herbs on Ornithonyssus sylviarum (Acari: Macronyssidae)

Ornithonyssus sylviarum (Acari: Macronyssidae) is a common ectoparasite that feeds on the blood of poultry. Following infestation, this mite will cause symptoms such as weight loss, anemia, and decreased egg production. To explore green and safe drugs for the prevention and treatment of O. sylviarum, this study evaluated the effects of ethanol extracts of seven Chinese medicinal herbs-Leonurus artemisia (motherwort), Illicium verum (star anise), Cinnamomum cassia (cinnamon), Hibiscus syriacus, Artemisia argyi (Chinese mugwort), Taraxacum sp. (dandelion), and Syzygium aromaticum (clove)-on O. sylviarum at different life stages. The results showed that different methods of administration affected the acaricidal efficacy of these plant extracts on O. sylviarum. After 6 h of administration with the fumigation method, the acaricidal efficacy of S. aromaticum on adults, nymphs and larvae of O. sylviarum reached 100%. 30 min after administration with the infiltration method, S. aromaticum, H. syriacus and L. artemisia showed acaricidal effects on adults and nymphs of O. sylviarum reaching 100%. In another experiment evaluating the inhibition of egg hatching of O. sylviarum with alcohol extracts of these seven herbs, at 48 h after treatment, A. argyi and C. cassia showed inhibition rates of 19.4%. The results of this study indicate that S. aromaticum induced mortality at all stages of O. sylviarum, whereas A. argyi was found to be the most effective at inhibiting the mite's egg hatching among the seven herbs. These herbs can therefore be used as potential substitutes for chemical pesticides to prevent and control O. sylviarum. These results provide practical knowledge for the control of O. sylviarum.

Evaluation of the activity of filamentous fungi isolated from soils of the Pampa biome applied in the biological control of Tetranychus urticae (Acari: Tetranychidae) and Polyphagotarsonemus latus (Acari: Tarsonemidae)

Tetranychus urticae Koch and Polyphagotarsonemus latus Banks are mite species considered capable of attaining pest levels, damaging a range of agricultural crops. The Pampa biome is characterized by the high biodiversity it houses, particularly microbial diversity, which highlights its potential for developing microorganisms that can provide biological control of arthropods. The aim of this study was to evaluate the activity of four fungal isolates from the soil of the Pampa biome in the biological control of T. urticae (females and eggs) and P. latus (females). Experiments consisted of isolating and identifying fungal isolates for spore quantification and aspersion at 10⁸, 10⁶, and 10⁴ spores/mL concentrations in arenas containing T. urticae females and eggs, and P. latus females, separately. Results indicated that only three isolates (Aspergillus brunneoviolaceus, Clonostachys chloroleuca, and Penicillium adametzii) showed high control of T. urticae females, yet they did not exhibit any control of T. urticae eggs and P. latus females. Therefore, the present study confirms the viability of some of these fungi as biological control agents of mites, which implies the importance of new prospects with other fungal species, considering the richness of resources in the Pampa biome, or even the need to test higher concentrations and other variables using the microorganisms of the present study.

Entomopathogenic Fungi and Bacteria in a Veterinary Perspective

Simple Summary

Several fungal species are well suited to control arthropods, being able to cause epizootic infection among them and most of them infect their host by direct penetration through the arthropod’s tegument. Most of organisms are related to the biological control of crop pests, but, more recently, have been applied to combat some livestock ectoparasites. Among the entomopathogenic bacteria, Bacillus thuringiensis, innocuous for humans, animals, and plants and isolated from different environments, showed the most relevant activity against arthropods. Its entomopathogenic property is related to the production of highly biodegradable proteins. Entomopathogenic fungi and bacteria are usually employed against agricultural pests, and some studies have focused on their use to control animal arthropods. However, risks of infections in animals and humans are possible; thus, further studies about their activity are necessary.

Abstract

The present study aimed to review the papers dealing with the biological activity of fungi and bacteria against some mites and ticks of veterinary interest. In particular, the attention was turned to the research regarding acarid species, Dermanyssus gallinae and Psoroptes sp., which are the cause of severe threat in farm animals and, regarding ticks, also pets. Their impact on animal and human health has been stressed, examining the weaknesses and strengths of conventional treatments. Bacillus thuringiensis, Beauveria bassiana and Metarhizium anisopliae are the most widely employed agents. Their activities have been reviewed, considering the feasibility of an in-field application and the effectiveness of the administration alone or combined with conventional and alternative drugs is reported.

Parasitic Mite Fauna in Asian Poultry Farming Systems

The ubiquitous presence of hematophagous avian mites threatens the poultry industry in Asia and worldwide, adversely affecting the quality and quantity of eggs and poultry meat produced by affected flocks. This leads to considerable economic loss and welfare-related issues. The role of these blood-feeding arthropods as disease vectors is increasingly recognized as they may carry important zoonotic and epizootic pathogens. The poultry mites, Dermanyssus gallinae (Poultry Red Mite-PRM), Ornithonysus sylviarum (Northern Fowl Mite-NFM), and Ornithonyssus bursa (Tropical Fowl Mite-TFM) are endemic species across the Asian continent. In less frequency, scaly leg mite, depluming mite, and fowl cyst mite were documented. Considering global climate change and the popularity of backyard farming, the incidence of avian mite infestation is expected to increase as Asian production expands. The TFM may start to colonize sub-tropical nations where the seasonal temperature is comparable to tropical regions. Pyrethroids, organophosphates, carbamates, and macrocyclic lactones are licensed acaricides for use in China, Japan, and India. In recent years, the development of acaricide resistance has compromised the efficacy of chemical control measures. Several botanical acaricides based on plant and fungal constituents are being investigated. Judicious integration of multiple approaches to manage poultry mite infestation is advised. In this article, we review the prevalence, geographical distribution, zoonotic potential, and control measures of avian mites in poultry farms in Asia.