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Scientific Article • Rev. Caatinga 38 • 2025 • https://doi.org/10.1590/1983-21252025v3812910rc linkcopy

Open-access Effectiveness of Baits Containing Entomopathogenic Fungi Against Gryllus assimilis

Eficácia de iscas contendo fungos entomopatogênicos no controle de Gryllus assimilis

AuthorshipSCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The use of entomopathogens, including entomopathogenic fungi, for biological control provides a viable alternative to chemical pesticides for pest management. Entomopathogenic fungi infect and cause epizootics in a wide range of insect orders, including Hemiptera, Lepidoptera, Coleoptera, Diptera, Hymenoptera, and Orthoptera. This study aimed to assess the insecticidal efficacy of the entomopathogenic fungi Metarhizium anisopliae, Beauveria bassiana, and Isaria fumosorosea against Gryllus assimilis (Orthoptera: Gryllidae) under laboratory conditions. The experiments were conducted using a completely randomized design with four replications. Two strains of B. bassiana (IBCB 66 and PL 63), one strain of M. anisopliae (E9), and one strain of I. fumosorosea (ESALQ 1296) were evaluated. The highest mortality of G. assimilis was observed seven days post-treatment with M. anisopliae at 0.15 g, resulting in resulting in over 50% insect mortality.

Keywords:
Biological control; Bioformulations; Insects; Cricket.

RESUMO

O controle biológico usando entomopatógenos, incluindo os fungos entomopatogênicos, oferece uma alternativa relativamente adequada para o manejo de pragas. Sabe-se que os fungos entomopatogênicos infetam e causam epizootias em uma ampla gama de ordens de insetos, incluindo Hemiptera, Lepidoptera, Coleoptera, Diptera, Hymenoptera e Orthoptera.. O objetivo do presente estudo foi avaliar a eficácia dos fungos entomopatogênicos Metarhizium anisopliae, Beauveria bassiana e Isaria fumosorosea sobre a mortalidade de Gryllus assimilis (Orthoptera: Gryllidae) em ambiente de laboratório. Os testes foram realizados em delineamento inteiramente casualizado, com 4 repetições. Foram avaliadas duas cepas de B. bassiana e uma cepa de M. anisopliae e I. fumosorosea. 7 dias após o tratamento com M. anisopliae 0,15g, foi observada a maior mortalidade de G. assimilis, tendo causado mortalidade de mais da metade dos insetos.

Palavras-chave:
Biocontrole; Bioformulações; Insetos; Microbiológicos.

INTRODUCTION

Crickets are omnivorous insects that feed on a wide variety of plant and animal material. Gryllus assimilis (Orthoptera: Gryllidae), for example, is known to damage eucalyptus plantations, plant nurseries, and seedlings during the first two years after planting, often necessitating replanting.

Pest management in agricultural production areas currently relies primarily on synthetic pesticides, which are widely recognized for controlling agricultural pests and enhancing crop yields (ANANI et al., 2020). However, these pesticides adversely affect soil microbial activity, reducing ecosystem services and the production of plant growth-promoting compounds such as siderophores, nitrogen, and indole-3-acetic acid. Moreover, synthetic pesticides contribute to environmental contamination through various pathways, including volatilization, improper disposal, spray drift, erosion, and leaching. Consequently, non-target plant species may be affected, reducing their photosynthetic capacity and seed production (HASHIMI; HASHIMI; RYAN, 2020). Furthermore, pesticide residues accumulating in water bodies can bioaccumulate in aquatic organisms and then in animals and humans through biomagnification, resulting in severe diseases, including cancer, kidney disease, skin rashes, and diabetes (MANFO et al., 2020). This highlights the importance of developing and implementing alternative pest management strategies that are environmentally friendly, costeffective, reliable, and sustainable (TUPE et al., 2017).

Entomopathogenic fungi are important biological control agents that have been studied globally for over a century. The earliest experiments were conducted in the nineteenth century by the Russian zoologist Metschnikoff, who investigated the efficacy of Metarhizium anisopliae for controlling a beetle species (VEGA et al., 2012).

Biological control using entomopathogenic fungi provides a viable alternative to chemical insecticides for pest management (TUPE et al., 2017). Entomopathogenic fungi infect and cause epizootics across a diverse range of insect orders, including Hemiptera, Lepidoptera, Coleoptera, Diptera, Hymenoptera, and Orthoptera (SHAH; PELL, 2019; ISLAM, 2021).

Entomopathogenic fungi exhibit parasitic behavior that can be utilized for the biological control of pests and diseases, representing the primary cause of microbial diseases in invertebrates. They comprise a diverse group of nearly 1,000 species, serving as natural mortality factors for insects and arachnids, including ticks and mites (HUMBER, 2008; BOOMSMA et al., 2014; STONE; BIDOCHKA, 2020). Unlike viruses, protozoa, and bacteria, which typically require specific infection pathways such as ingestion, most entomopathogenic fungi infect arthropods by directly penetrating the host's cuticle, primarily functioning as contact pathogens (MASCARIN et al., 2016).

Although the primary mode of infection is through the integument, evidence suggests that B. bassiana can also infect insects via ingestion, particularly those with chewing mouthparts (FENG; POPRAWSKI; KHACHATOURIANS, 1994). Metarhizium anisopliae (Metsch) Sorokin (Ascomycota: Clavicipitaceae) is a naturally occurring entomopathogen, parasitizing insects across diverse habitats, and its use as a biological control agent in pest-infested areas has become widespread in Brazil (ALMEIDA, 2020).

Entomopathogenic fungi are important biological pest control agents capable of colonizing a diverse range of pests and causing epizootic diseases that lead to mortality or disrupt feeding and reproduction in insects and mites (SHARMA; SHARMA; YADAV, 2023; ROHRIG, 2021). These fungi typically infect insects by penetrating their cuticle, regardless of the insect's feeding habits. As the insect cuticle serves as the primary barrier to fungal infection, entomopathogenic fungi produce several extracellular enzymes that degrade proteins, chitin, and lipids, which are the main components of the cuticle (PEDRINI; CRESPO; JUÁREZ, 2007; VEGA et al., 2012).

This study aimed to assess the insecticidal efficacy of the entomopathogenic fungi Metarhizium anisopliae, Beauveria bassiana, and Isaria fumosorosea against Gryllus assimilis (Orthoptera: Gryllidae) under laboratory conditions. The efficacy of the tested fungi in causing infections by contact and ingestion was evaluated using different pathogen concentrations and post-treatment times.

MATERIAL AND METHODS

Gryllus assimilis rearing

The Gryllus assimilis population, reared at the Federal University of Pelotas (UFPEL), in Pelotas, RS, Brazil, was sourced from the Terrestrial Invertebrate Vivarium, Institute of Biological Sciences, Federal University of Rio Grande (FURG). The G. assimilis population was maintained at the Insect Biology Laboratory, Department of Ecology, Zoology and Genetics, Biology Institute (DEZG/IB/UFPEL), following the protocols of Limberger, Nery and Fonseca (2021), under controlled temperature of 25 ± 2 °C, relative humidity of 65 ± 10%, and a 12-hour photoperiod. Crickets were provided ad libitum access to commercial cat feed (Golden, PremieRpet® São Paulo, Brazil) from egg hatching and supplied with water on wet cotton, which was replaced daily.

Bioinsecticide product formulations and treatments

Microbiological insecticides, formulated as emulsifiable concentrates (EC) or wettable powders (WP), were supplied by Koppert do Brasil Holding Ltd., Piracicaba, SP, Brazil. The products included: (i) Boveril Cana®, containing 30 g kg-1 of the active ingredient (AI) Beauveria bassiana (Bals.) Vuill. strain IBCB 66 (1.5 × 109 CFU g-1); (ii) Boveril® WP, containing 50 g kg-1 of the AI B. bassiana strain PL63 (1 × 108 viable conidia g-1; (iii) Metarril® WP E9, containing 50 g kg-1 of the AI Metarhizium anisopliae (Metsch.) Sorokin strain E9 (1.39 × 108 viable conidia g-1); and (iv) Challenger® EC, containing 85 g L-1 of the AI Isaria fumosorosea Wize strain ESALQ 1296 (2.5 × 109 viable conidia mL-1) (Table 1).

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Table 1
Microbiological insecticides used in laboratory bioassays against Gryllus assimilis.

Bioassay

Effect of entomopathogenic fungi on mortality of Gryllus assimilis adults through ingestion

The experiment was conducted at the Insect Biology Laboratory (DEZG/IB/UFPEL). The four microbiological insecticides (Table 1) were tested at concentrations of 5%, 10%, and 15%, with distilled water serving as a negative control. A completely randomized design with 13 treatments and four replications was used, resulting in 52 experimental units. Each experimental unit consisted of a 700 mL plastic container with a 1 cm diameter hole on the side, covered with a lid. The container held a plastic cup (4 cm height and 4 cm diameter) containing 5 g of commercial feed mixed with the entomopathogenic fungi product. Four unsexed adult G. assimilis, aged seven to ten days after preimaginal molting, were placed in each container, totaling 208 individuals. Adults were fasted for 24 hours to encourage rapid feeding.

Solutions were prepared using the microbiological insecticides at the concentrations tested, with 0.05, 0.10, or 0.15 g (WP), or 0.05, 0.10, or 0.15 mL (EC) diluted in 50 mL of distilled water. The solutions were applied to the feed surface by spraying 2 mL of the solution per 5 g of feed, which was then offered to the insects. Mortality due to fungal infection was assessed daily for eight days, with the dead insects collected and incubated in a biochemical oxygen demand (BOD) chamber at 25 °C, 60% relative humidity, and a 12-hour photoperiod for seven days to confirm mycelium growth.

Effect of entomopathogenic fungi on mortality of Gryllus assimilis nymphs and adults through contact

This experiment was conducted using a completely randomized design with 18 treatments and four replicates, resulting in 72 experimental units. Each experimental unit consisted of a 700 mL plastic container with a perforated lid to ensure ventilation. Four insects were placed in each container, totaling 256 individuals, comprising 128 pre-adult nymphs and 128 adults. The four microbiological insecticides (Table 1) were tested. Solutions were prepared with 20 g and 30 g of each product, using the same method as that described for the previous experiment. The applications consisted of spraying 2 mL of the solution onto the insects in each experimental unit.

Insect mortality due to fungal infection was assessed daily for 6 days, with dead insects incubated as described for the previous experiment. Mortality percentages (M%) were calculated relative to the control, using the formula of Schneider-Orelli (1947: M% = 100 × (Mt - Mc) ÷ (100 - Mc), where Mt is the mortality in the insecticide treatment and Mc is the mortality in the control treatment.

Data analysis

Mortality data for G. assimilis, collected over eight days post-treatment in the first experiment and six days posttreatment in the second experiment, were tested for normality using the Shapiro-Wilk test and for homogeneity of variances using the Bartlett test. When the data did not meet normality criteria, they were transformed using the formula √x + 0.5 to satisfy the assumptions of analysis of variance (ANOVA), for each post-treatment evaluation period. Cumulative mortality data were analyzed using ANOVA, with the F-test to evaluate interactions between factors (products and concentrations). The data were then analyzed using polynomial regression in R software (R DEVELOPMENT CORE TEAM, 2023).

RESULTS AND DISCUSSION

Effect of entomopathogenic fungi on mortality of Gryllus assimilis adults through ingestion

Mortality rates over time for G. assimilis adults, resulting from the application of four entomopathogenic fungal insecticides at different concentrations, generally followed a polynomial distribution. The results indicate that these fungal products are promising biological insecticides against crickets, as incorporation of fungal conidia into feed caused high mortality in G. assimilis adults under laboratory conditions.

One day after treatment (DAT), the interaction between factors (product and concentration) was not significant for Boveril Cana® (F = 1.14, Fstat = 1.10, p = 0.3034). Significant interactions were observed for Boveril® (F = 6.47, Fstat = 13.08, p = 0.0244), Metarril® (F = 8.34, Fstat = 4.53, p = 0.0127), and Challenger® (F = 11.29, Fstat = 6.99, p = 0.0051). The highest mortality for G. assimilis (18.75%) was observed with Challenger® at a 10% concentration (Figure 1A). These results align with those of Meikle et al. (2005), who evaluated three B. bassiana isolates and one I. fumosorosea isolate against Coptotermes formosanus in Hong Kong, China, under laboratory conditions. In preliminary bioassays, I. fumosorosea Pfu02031 was the most effective, achieving 100% mortality of C. formosanus, followed by I. fumosorosea Pfu02031 combined with a commercial M. anisopliae isolate (Bioblast®). Although no significant difference was observed among the fungi tested against C. formosanus, when infected and uninfected termites were grouped, I. fumosorosea Pfu02031 was significantly more pathogenic, resulting in the lowest mean survival of insects.

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Figure 1
Daily mortality of Gryllus assimilis adults subjected to different concentrations (5%, 10%, and 15%) of entomopathogenic fungibased products (Boveril Cana®, Boveril®, Metarril®, and Challenger®), under laboratory conditions, assessed at 1 (A), 2 (B), 3 (C), 4 (D), 5 (E), 6 (F), and 7 (G) days after treatment.

At two DAT, the interaction between factors (product and concentration) was not significant for Boveril Cana® (F = 1.16, Fstat = 1.12, p = 0.3000). Significant interactions were observed for Boveril® (F = 154.84, Fstat = 84.39, p = 0.0001), Metarril® (F = 5.22, Fstat = 15.82, p = 0.0398), and Challenger® (F =9.28, Fstat = 5.04, p = 0.0094). The highest mortality rate for G. assimilis (25%) was observed with Metarril® and Challenger® at 5% and 10% concentrations, respectively (Figure 1B). Similar results were reported by Lacey et al. (2011), who evaluated Metarhizium anisopliae, Isaria fumosorosea, and the insecticide abamectin against the potato psyllid (Bactericera cockerelli Sulc) under field conditions, observing reductions in egg production and nymph survival compared to the control, which only mitigated plant damage.

At three DAT, the interaction between factors (product and concentration) was not significant for Boveril Cana® (F = 3.44, Fstat = 2.50, p = 0.0861). Significant interactions were observed for Boveril® (F = 0.82, Fstat = 72.29, p = 0.0381), Metarril® (F = 9.77, Fstat = 18.94, p = 0.0080), and Challenger® (F = 53.56, Fstat = 29.18, p = 0.0001). The highest mortality rate for G. assimilis (37.5%) was observed with Boveril® at a 5% concentration. Challenger® at 5% and Metarril® at 15% also caused significant mortality rates of approximately 31.25% (Figure 1C).

At four DAT, significant interactions between factors (product and concentration) were observed for Boveril Cana® (F = 4.75, Fstat = 4.75, p = 0.0210), Metarril® (F = 20.20, Fstat = 16.88, p = 0.0012), and Challenger (F = 35.56, Fstat = 65.29, p < 0.0001). The highest mortality rate for G. assimilis (approximately 37.5%) was observed with Boveril Cana® at a 10% concentration. In contrast, no interaction was observed for Boveril® (F = 0.51, Fstat = 44.95, p = 0.4876) (Figure 1D).

At five DAT, significant interactions between factors (product and concentration) were observed for Boveril Cana® (F = 9.86, Fstat = 6.27, p = 0.0078), Metarril® (F = 9.75, Fstat = 8.57, p = 0.0085), and Challenger® (F = 51.83, Fstat = 28.23, p < 0.0001). In contrast, no significant interaction was observed for Boveril® (F = 0.56, Fstat = 49.13, p = 0.4684). The highest mortality rate for G. assimilis (43.75%) was observed with Boveril Cana® at a 10% concentration, followed by Boveril® at 15%, with 37.5% mortality (Figure 1E). Similar results were reported by Pelizza et al. (2019), who evaluated B. bassiana using various baits against the locust Dichroplus maculipennis under field conditions, in cages. They observed that bait containing wheat bran and B. bassiana conidia caused significant mortality in locusts, and mixtures of Boveril Cana®, Boveril®, Metarril®, and Challenger® with feed acted as toxic baits, leading to death of G. assimilis individuals.

At six DAT, significant interactions between factors (product and concentration) were observed for Boveril Cana® (F = 9.74, Fstat = 6.20, p = 0.0081), Metarril® (F = 24.55, Fstat = 16.73, p = 0.0003), and Challenger® (F = 24.27, Fstat = 47.28, p < 0.0001). In contrast, no significant interaction was observed for Boveril® (F = 0.49, Fstat = 58.59, p = 0.4962). The highest mortality rate for G. assimilis (43.75%) was observed with Boveril® at a 15% concentration, followed by Metarril® and Challenger® at 5%, each with 37.5% mortality (Figure 1F). These results align with those reported by Konar and Santanu Paul (2005), who evaluated the efficacy of granular insecticides and biopesticides against the mole cricket Gryllotalpa spp. (Orthoptera: Gryllotalpidae) in potato cultivars under field conditions. They reported the highest control efficacy for the biopesticides M. anisopliae at 1.8 × 109 spores mL-1 at 50 g ha-1 and B. bassiana at 108 spores applied at 1,000 g ha-1.

At seven DAT, significant interactions between factors (product and concentration) were observed for Boveril Cana® (F = 26.52, Fstat = 15.68, p = 0.0002), Boveril® (F = 6.67, Fstat = 31.10, p = 0.0227), Metarril® (F = 10.55, Fstat = 24.43, p = 0.0058), and Challenger® (F = 46.42, Fstat = 27.35, p < 0.0001). The highest mortality rate for G. assimilis (56.25%) was observed with Metarril® at a 15% concentration (Figure 1G). These results align with those reported by Hanel (1982), who evaluated the insecticidal efficacy of M. anisopliae against the termite Nasutitermes exitiosus (Hill), using a concentration of 1.29 × 107 conidia mL-1 and observed over 95% mortality after 11 days.

At eight DAT, significant interactions between factors (product and concentration) were observed for Boveril Cana® (F = 23.85, Fstat = 12.83, p = 0.0003), Boveril® (F = 11.95, Fstat = 16.50, p = 0.0042), Metarril® (F = 10.85, Fstat = 24.43, p = 0.0048), and Challenger®. The highest mortality rate for G. assimilis (37.33%) was observed with Metarril® at a 10% concentration (Figure 2).

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Figure 2
Cumulative mortality of Gryllus assimilis adults subjected to different concentrations (5%, 10%, and 15%) of entomopathogenic fungi-based products (Boveril Cana®, Boveril®, Metarril®, and Challenger®), under laboratory conditions, assessed up to eight days after treatment.

Treatments with Metarril® and Challenger® resulted in a gradual reduction in the number of live G. assimilis insects. Treatments with Metarril® and Boveril® achieved the highest mortality rates, exceeding 50%, by the end of the experiment. Additionally, the treatment with Challenger® resulted in the third highest mortality rate (43.75%). Reductions in the number of live insects were approximately 43.75% for Metarril® and 68.75% for Boveril Cana®, each applied at 15% concentration (Figure 2).

Dead insects that were collected and incubated in a BOD chamber under controlled conditions exhibited no mycelial growth, regardless of the fungal treatment applied. This may be attributed to mechanisms involved in adhesion, which are not yet fully elucidated. Certain enzymes may be associated with the aggressiveness of specific fungi, and insect mortality results from a complex series of events, making it challenging to correlate fungal treatment with mortality (ALVES, 1986).

Effect of entomopathogenic fungi on mortality of Gryllus assimilis nymphs and adults through contact

Nymphs

At one day after treatment (DAT), nymph mortality differed significantly among treatments (F = 15.10, p = 0.0001). The highest mortality rate for G. assimilis nymphs (88%) was observed with Boveril® at 30 g, followed by Boveril Cana® at 30 g (57%) and Challenger® at 20 g (51%). The lowest mortality rates were observed with Boveril® at 20 g (39%) and Challenger® at 30 g (48%). Boveril Cana® at 20 g and Metarril® at 20 g and 30 g resulted in no mortality (Table 2).

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Table 2
Mean mortality and percentage mortality (M%) of Gryllus assimilis nymphs treated with entomopathogenic fungi-based products [Boveril Cana® (BC), Boveril® (BO), Metarril® (ME), and Challenger® (CH)] in contact bioassays using 20 g (20) and 30 g (30) of each product, under laboratory conditions, assessed up to six days after treatment (DAT).

At two DAT, nymph mortality differed significantly among treatments (F = 4.51, p = 0.0010). However, only Boveril® at 20 g resulted in a significant mortality rate (13%) compared to the control, while the other treatments resulted in no mortality (Table 2). At three DAT, nymph mortality did notdiffersignificantlyamongtreatments(F=3.38, p = 0.2993) (Table 2).

At four DAT, nymph mortality differed significantly among treatments (F = 5.66, p = 0.0002). The highest mortality rate for nymphs (42%) was observed with Metarril® at 20 g (Table 2). At five DAT, nymph mortality did not differ significantly among treatments (F = 0.75, p = 0.6479) (Table 2).

At six DAT, nymph mortality differed significantly among treatments (F = 3.54, p = 0.0060). The highest mortality rate for nymphs (22%) was observed with Challenger® at 20 g, followed by Metarril® at 20 g and Challenger® at 30 g, each with 13% (Table 2).

Adults

At one day after treatment (DAT), adult mortality 3). At five DAT, adult mortality differed significantly among treatments (F = 7.05, p = 0.0010). The highest mortality rate for G. assimilis adults (26%) was observed with Challenger® differed significantly among treatments (F = 4.89, p = 0.0008). The highest mortality rate for G. assimilis adults (57%) was observed with Boveril® at 30 g, followed by Boveril® at 20 g (26%) and Boveril Cana® at 30 g (22%). A mortality rate of 13% was observed with Challenger® at 20 g and 30 g. Boveril Cana® at 20 g and Metarril® resulted in no mortality (Table 3).

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Table 3
Mean mortality and percentage mortality (M%) of Gryllus assimilis adults treated with entomopathogenic fungi-based products [Boveril Cana® (BC), Boveril® (BO), Metarril® (ME), and Challenger® (CH)] in contact bioassays using 20 g (20) and 30 g (30) of each product, under laboratory conditions, assessed up to six days after treatment (DAT).

At two DAT, adult mortality differed significantly among treatments (F = 3.54, p = 0.0060). The highest mortality rate for adults (22%) was observed with Metarril® at 20 g, whereas a mortality rate of 13% was observed with Boveril® at 20 g and Challenger® at 20 g. At three DAT, adult mortality differed significantly among treatments (F = 4.51, p = 0.001. However, only Boveril® at 20 g resulted in a significantly different mortality rate (13%), whereas the other treatments resulted in no mortality (Table 3).

At four DAT, adult mortality differed significantly among treatments (F = 4.39, p = 0.0010). The highest mortality rate for adults (51%) was observed with Boveril Cana® at 30 g, followed by Boveril Cana® at 20 g and Metarril® 20 g, each with 26%. Boveril® at 20 g and 30 g, as well as Challenger® at 20 g, resulted in 13% mortality (Table at 20 g, whereas Metarril® at 20 g resulted in 22% mortality (Table 3).

At six DAT, adult mortality differed significantly among treatments (F = 3.10, p = 0.013. The highest mortality rate for adults (35%) was observed with Challenger® at 30 g, followed by Metarril® at 30 g and Boveril® at 20 g, each with 26% mortality. Challenger® at 20 g, Metarril® at 20 g, and Boveril Cana® at 30 g resulted in 13% mortality (Table 3).

Dead insects that were collected and incubated in a BOD chamber for seven days exhibited reduced mycelial growth, confirming mortality caused by fungal infection. Microbiological insecticides based on the fungi M. anisopliae and B. bassiana are effective in controlling insect pests. These fungi are among the most promising microbial control agents, particularly for soil-dwelling insects. According to Feng Poprawski and Khachatourians. (1994), B. bassiana is a natural soil-dwelling microbiological agent pathogenic to over 200 insect species. The efficacy of these entomopathogenic fungi depends on their persistence in the pest's microenvironment and the selection of specific strains for suitable hosts (EL-GARHY, 2011).

The strains of entomopathogenic fungi evaluated (B. bassiana IBCB 66, B. bassiana PL 63, M. anisopliae E9, and Isaria fumosorosea ESALQ 1296) infect insects across nearly all orders, particularly Hemiptera, Coleoptera, Lepidoptera, Orthoptera, and Hymenoptera (RAMANUJAM et al., 2024; MAINA et al., 2018). They have demonstrated entomopathogenic activity against various arthropods, including Cosmopolites sordidus Germar (Coleoptera: Curculionidae), Dalbulus maidis (Hemiptera: Cicadellidae), Gonipterus scutellatus (Coleoptera: Curculionidae), Mahanarva fimbriolata (Hemiptera: Cercopidae), Diatraea saccharalis (Lepidoptera: Pyralidae), Amblyomma cajennense (Acari: Ixodidae), and Helicoverpa armigera (Lepidoptera: Noctuidae) (LOPES et al., 2007).

Overall, mortality rates increased with higher concentrations of the applied products, but average feed consumption varied significantly among treatments and concentrations. Conidia of M. anisopliae E9 (Metarril®) were not repellent to G. assimilis, and reductions in the number of insects were associated with bait feeding and product concentrations, causing over 50% mortality of G. assimilis. Thus, products based on B. bassiana and M. anisopliae conidia were not repellent and can be incorporated into baits for controlling G. assimilis.

CONCLUSION

The results demonstrate that the entomopathogenic fungi Metarhizium anisopliae, Beauveria bassiana, and Isaria fumosorosea cause mortality in Gryllus assimilis. The pathogenicity of these fungi, applied at different concentrations, varied over time after application. In contact assays, Boveril® and Challenger® caused the highest mortality rates in G. assimilis (88% and 51%, respectively) one day after application. In ingestion assays, Metarril® at 15% resulted in a mortality rate of 56% in insects. Among the evaluated entomopathogenic fungal insecticides, Boveril®, Challenger®, and Metarril® were the most effective. Notably, Metarril® achieved the highest cumulative mortality when applied through ingestion, making it suitable for incorporation into toxic baits for controlling G assimilis. Therefore, the use of these entomopathogenic fungi offers an effective and environmentally friendly alternative for controlling G assimilis, particularly given the nocturnal habit of crickets, remaining hidden during the day under trunks, tree bark, and soil mulch.

ACKNOWLEDGEMENTS

The authors thank the Brazilian Coordination for the Improvement of Higher Education Personnel (CAPES), for granting a master's scholarship to ADS; the Brazilian National Council for Scientific and Technological Development (CNPq) for providing a productivity scholarship to FRMG; the Koppert company and the Federal University of Rio Grande (FURG) for supplying experiment materials; and Daniel Soares Duarte and Lúcia Maciel for their translation assistance.

Data Availability:

The data that support the findings of this study can be made available, upon reasonable request, from the corresponding author .

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Edited by

  • Editor in Chief:
    Aurélio Paes Barros Júnior
  • Section Editor:
    Carlos Henrique Brito

Publication Dates

  • Publication in this collection
    25 Aug 2025
  • Date of issue
    2025

History

  • Received
    27 Aug 2024
  • Accepted
    31 Mar 2025
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This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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