Impacts of fungal entomopathogens on survival and immune responses of Aedes albopictus and Culex pipiens mosquitoes in the context of native Wolbachia infections

Microbial control of mosquitoes via the use of symbiotic or pathogenic microbes, such as Wolbachia and entomopathogenic fungi, are promising alternatives to synthetic insecticides to tackle the rapid increase in insecticide resistance and vector-borne disease outbreaks. This study evaluated the susceptibility and host responses of two important mosquito vectors, Ae. albopictus and Cx. pipiens, that naturally carry Wolbachia, to infections by entomopathogenic fungi. Our study indicated that while Wolbachia presence did not provide a protective advantage against entomopathogenic fungal infection, it nevertheless influenced the bacterial / fungal load and the expression of select anti-microbial effectors and phenoloxidase cascade genes in mosquitoes. Furthermore, although host responses from Ae. albopictus and Cx. pipiens were mostly similar, we observed contrasting phenotypes with regards to susceptibility and immune responses to fungal entomopathogenic infection in these two mosquitoes. This study provides new insights into the intricate multipartite interaction between the mosquito host, its native symbiont and pathogenic microbes that might be employed to control mosquito populations.

Colonzation of Tobacco Plants by Fungal Entomopathogens and the Effect on Consumption over Diabrotica speciosa (Coleoptera: Chrysomelidae)

Entomopathogenic fungi are naturally occurring microorganisms that attack insect pests, making them exceptional allies when developing biocontrol strategies. A particular aspect of the ecology of these fungi is that they interact not only with insects but also with plants, being able to colonize them endophytically without causing symptoms of disease. The objectives of this study were to determine the endophytic capacity of different species of entomopathogenic fungi in tobacco plants by means of foliar spraying, to evaluate the persistence in planta of the entomopathogens and the effect of endophytes on consumption by coleopteran pests. A total of 24 strains were analyzed to test endophytic capacity at 7, 14, 21 and 28 days post inoculation. A significant effect of the strains was found. On days 7, 14 and 21, the strain that showed the highest colonization percentages was B. bassiana LPSc 1215, and at day 28 B. bassiana strains LPSc 1215 and LPSc 1212 exhibited the best endophytic capacity, maintaining elevated colonization percentages. Choice test results indicated that D. speciosa fed indiscriminately on colonized and non-colonized leaves. The results indicate that B. bassiana LPSc 1215 constitutes a strain that would merit further investigation for the purpose of pest management in tobacco cultivation.

General Limitations to Endophytic Entomopathogenic Fungi Use as Plant Growth Promoters, Pests and Pathogens Biocontrol Agents

The multiple roles of fungal entomopathogens in host plants’ growth promotion, pest and pathogen management have drawn huge attention for investigation. Endophytic species are known to influence various activities of their associated host plants, and the endophyte-colonized plants have been demonstrated to gain huge benefits from these symbiotic associations. The potential application of fungal endophytes as alternative to inorganic fertilizers for crop improvement has often been proposed. Similarly, various strains of insect pathogenic fungi have been formulated for use as mycopesticides and have been suggested as long-term replacement for the synthetic pesticides that are commonly in use. The numerous concerns about the negative effects of synthetic chemical pesticides have also driven attention towards developing eco-friendly pest management techniques. However, several factors have been underlined to be militating the successful adoption of entomopathogenic fungi and fungal endophytes as plant promoting, pests and diseases control bio-agents. The difficulties in isolation and characterization of novel strains, negative effects of geographical location, vegetation type and human disturbance on fungal entomopathogens, are among the numerous setbacks that have been documented. Although, the latest advances in biotechnology and microbial studies have provided means of overcoming many of these problems. For instance, studies have suggested measures for mitigating the negative effects of biotic and abiotic stressors on entomopathogenic fungi in inundative application on the field, or when applied in the form of fungal endophytes. In spite of these efforts, more studies are needed to be done to achieve the goal of improving the overall effectiveness and increase in the level of acceptance of entomopathogenic fungi and their products as an integral part of the integrated pest management programs, as well as potential adoption as an alternative to inorganic fertilizers and pesticides.

Mechanisms behind the Madness: How Do Zombie-Making Fungal Entomopathogens Affect Host Behavior To Increase Transmission?

Transmission is a crucial step in all pathogen life cycles. As such, certain species have evolved complex traits that increase their chances to find and invade new hosts.

Identifying and detecting Entomopathogenic fungi using Surface-enhanced Raman spectroscopy / Identificação e detecção de fungos entomopatogênicos utilizando Superficie-enhanced Raman espalhamento

In the natural ecosystem, fungal entomopathogens are the most efficient biocontrol agents against insect pests. In this study we offer an alternative for conventional fungal diagnostic, Surface-enhanced Raman spectroscopy (SERS) technique combine with principal component analysis (PCA) for detection and identification three entomopathogenic fungi, namely, IBCB 66 Beauveria bassiana, IBCB 130 Isaria fumosorosea, and IBCB 425 Metarhizium anisopliae. Using a simple preparation approach, highly active silver nanoparticles suitable for detecting complex biomolecules were produced for application in the SERS technique. Entomopathogens fungi produced highly enhanced and reproducible Raman signals based on their biochemical composition due to the high density of hot spots at the confluence of silver nano-aggregates, allowing the three entomopathogens species to be differentiated in the SERS spectrum fingerprint region, 550-1700 cm-1. The SERS method, along with PCA analysis, accounted for over 99 % of total variance and allowed for very high probability discrimination between the three entomopathogens, allowing taxonomic affiliation to be determined in a short period of time. These findings suggest that the SERS methodology can be used to develop a new, fast, accurate, and cost-effective diagnostic method for fungal entomopathogens.

Host-Environment Interplay Shapes Fungal Diversity in Mosquitoes

The Asian tiger mosquito, Aedes albopictus , is the dominant mosquito species in the United States and an important vector of arboviruses of major public health concern. One aspect of mosquito control to curb mosquito-borne diseases has been the use of biological control agents such as fungal entomopathogens.

Alkane-priming of Beauveria bassiana strains to improve biocontrol of the redbanded stink bug Piezodorus guildinii and the bronze bug Thaumastocoris peregrinus

Insect Epicuticle hydrocarbons (CHC) are known to be important determinants in the susceptibility degree of insects to fungal entomopathogens. Five Beauveria bassiana isolates were phenotypically analyzed regarding their response to CHC nutrition and their pathogenicity and virulence towards high fungal-susceptible Thaumastocoris peregrinus and low fungal-susceptible Piezodorus guildinii, which are important hemipteran pests in eucalyptus and soybean plantations, respectively. Two of these isolates, resulting the most (ILBB308) and the least (ILBB299) virulent to P. guildinii, were also evaluated at gene expression level after growth on n-pentadecane. B. bassiana most virulent isolate ILBB308 showed the lowest growth on most evaluated CHC media. However, this isolate distinctively induced most of the analyzed genes involved in CHC assimilation, cuticle degradation and stress tolerance. Virulence towards low susceptibility P. guildinii was enhanced in both hypervirulent ILB308 and hypovirulent ILBB299 isolates after growth on n-pentadecane as the sole carbon source, whereas virulence enhancement towards high susceptibility T. peregrinus was not observed in alkane-grown fungi. Virulence enhancement towards P. guildinii could be mostly explained by a priming effect produced by CHC on the induction of some genes related to hydrocarbon assimilation in ILB 205 and ILB 308, such as hydrophobin (Bbhyd2) and cytochrome P450 genes (BbCyp52g11 and BbCyp52x1), and partially by the induction of genes related to cuticle degradation (Bbchit and Bbcdep1) and stress tolerance (Bbsod1) observed only in ILB308.

Evaluation of indigenous fungal entomopathogens and aqueous leaf extract of Annona muricata against Polyphagotarsonemus latus infesting Jatropha curcas in Indonesia

Puspitarini RD, Afandhi A, Fernando I. 2021. Evaluation of indigenous fungal entomopathogens and aqueous leaf extract of Annona muricata against Polyphagotarsonemus latus infesting Jatropha curcas in Indonesia. Biodiversitas 22: 2648-2655. The broad mite Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) has been known to cause a great deal of injury on Jatropha curcas (L.) plantation in Indonesia. Isolation of indigenous fungal entomopathogens from rhizosphere soils, followed by pathogenicity assay was conducted to find an effective isolate for controlling P. latus. Additionally, the potential combination of the selected isolate and soursop (Annona muricata L.) aqueous leaf extract (SLE) was investigated. A total of 24 isolates were obtained by using the insect bait method. Four fungal isolates, namely Paecilomyces sp. 1., Lecanicillium sp., Beauveria sp., and Fusarium sp. 1, showed high conidial viability and were chosen as representatives to assess their pathogenicity against P. latus. Among the tested isolates, Beauveria sp. which had the highest conidial viability among the tested isolates, needed a shorter period to completely kill the tested mites. However, the compatibility test revealed the deleterious effect of SLE on Beauveria sp. SLE at all concentrations showed a very toxic effect on the fungus, therefore the two must be applied separately. Our results provide useful information on the effectiveness of indigenous entomopathogenic fungi Beauveria sp. and aqueous leaf extract of A. muricata as an alternative tool to control the broad mite P. latus on the J. curcas plantation.

Empirical Support for the Pattern of Competitive Exclusion between Insect Parasitic Fungi

Fungal entomopathogens are largely facultative parasites and play an important role in controlling the density of insect populations in nature. A few species of these fungi have been used for biocontrol of insect pests. The pattern of the entomopathogen competition for insect individuals is still elusive. Here, we report the empirical competition for hosts or niches between the inter- and intra-species of the entomopathogens Metarhizium robertsii and Beauveria bassiana. It was found that the synergistic effect of coinfection on virulence increase was not evident, and the insects were largely killed and mycosed by M. robertsii independent of its initial co-inoculation dosage and infection order. For example, >90% dead insects were mycosed by M. robertsii even after immersion in a spore suspension with a mixture ratio of 9:1 for B. bassiana versus M. robertsii. The results thus support the pattern of competitive exclusion between insect pathogenic fungi that occurred from outside to inside the insect hosts. Even being inferior to compete for insects, B. bassiana could outcompete M. robertsii during co-culturing in liquid medium. It was also found that the one-sided mycosis of insects occurred during coinfection with different genotypic strains of either fungi. However, parasexual recombination was evident to take place between the compatible strains after coinfection. The data of this study can help explain the phenomena of the exclusive mycosis of insect individuals, but co-occurrence of entomopathogens in the fields, and suggest that the synergistic effect is questionable regarding the mixed use of fungal parasites for insect pest control.

Fungal entomopathogens: a systematic review

Background Apprehensions about the safety and the environment regarding the insecticidal application against insect infestations have directed our attention toward advancement of biological mediators so that they are assimilated into the concept of integrated pest management stratagems to develop a more practical approach for the management of insect pests. Management of insect pests by making use of biological approaches (such as fungal entomopathogens (EPF) or others which are antagonistic to insect population) provides a substitute approach which reduces the continuous use of chemical amalgams against insect pests. Main body The present review provides a framework of the present status of information on EPF as it identifies with their current use as biological control of pest infestations. To utilize a variety of biological control methodologies against insect hosts, it is essential to improve our comprehension of the ecology of EPF and also their role in nature. This article may assist us with understanding the virulence and the virulence factors related with EPF and present the latest developments and accomplishments in the significant field. We focus on recent instances of studies that show the overall patterns in interactions among insect pests and EPF prompting the advancement of epizootics. Also, we sum up the topical discoveries on current status of mycoinsecticides and propose future research needs. Conclusions As the current mechanism of fungal pathogenesis on insects is moderately slow and needs improvement, there is likewise the requirement for additional comprehension of the interactions among entomopathogens and insect pests so as to grow soundly planned procedures by identifying potential targets and via the improvement of fungal strains for improving the adequacy of these organisms in field applications.