Entomopathogenic fungi based microbial insecticides and their physiological and biochemical effects on Spodoptera frugiperda (J.E. Smith)

Abstract

Background‘The fall armyworm, Spodoptera frugiperda’, represents a significant threat to maize production, a major staple crop in Asian countries.MethodsIn pursuit of more effective control of this insect pest, our study assessed the physiological and biochemical effects of the entomopathogenic fungus Metarhizium anisopliae against the larvae of S. frugiperda.ResultsResults revealed that, following nine days of treatment, a high concentration of conidia (1.5x107 conidia/mL-1) was toxic to all stages of larvae (second to fifth instar), resulting in 97% mortality of the second instar, 89% mortality of the third instar, 77% mortality of the fourth instar, and 72% mortality of fifth instar. All larval instars were found to have dose-dependent mortality effects. Treated S. frugiperda larvae further displayed significant physiological, morphological, and behavioral changes. Here, treated larvae displayed significantly lower levels of acetylcholinesterase, α-carboxylesterase, and β-carboxylesterase enzyme activity when compared to control groups. Treated larvae underwent an outward morphological change as the result of a decrease in the exterior cuticle of the anal papillae and a demelanization of the interior cuticle. Treated larvae also exhibited abnormal feeding behaviors as a consequence of the negative impact of conidia treatment on the neuromuscular system. Investigation into the effect of M. anisopliae on the non-target organism, the earthworm Eudrilus eugeniae, revealed that M. anisopliae conidia did not produce significant pathogenicity following three days of treatment. Furthermore, histological analysis revealed no significant effect of the entomopathogenic fungi on the gut tissue of the non-target organism.ConclusionThis study highlights the potential of M. anisopliae in the control of S. frugiperda.

Biocontrol effects of chemical molecules derived from Beauveria bassiana against larvae of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

“…We first confirmed the morphology of the fungi species by microscopic observations of the fungal colony, pigment production, mycelium structures, and spore shape, following the steps we described in Kumar et al (2023) and Vivekanandhan et al (2023) . On the clean slide, one drop of lactophenol cotton blue (LCB) stain (HiMedia, India) was mixed with one loop of fungal conidia and thoroughly blended.…”

“…Plates were kept at a relative humidity of 85% and a temperature of 26 ± 2°C for 7 to 10 days. The pure fungal cultures were isolated from the dead larval cadaver according to Balumahendhiran et al (2019) and Vivekanandhan et al (2023) and preserved in a biochemical oxygen demand incubator (BOD) (Smartscience, India) at 26 ± 2°C for future experiments.…”

“…Entomopathogenic fungi B. bassiana (GenBank: OM346715.1) were sub-cultured on sterilized PDA fungal culture medium with ampicillin (2.7 mg/100 mL) and incubated at 26 ± 2°C for 7–10 days. The liquid broth culture medium for mass culturing of fungi was prepared using our previously established method ( Vivekanandhan et al, 2023 ). Four 500-mL conical flasks were sterilized at 15 psi for 30 min, each containing 250 mL of potato dextrose broth (PDB), composed of 20 g of dextrose, 5 g of peptone, and 1,000 mL of deionized water.…”

“…Numerous studies have investigated entomopathogenic fungi, conidia, and their chemical components for controlling T. absoluta insect pests, demonstrating their high effectiveness ( Zekeya et al, 2019 ; Bali and Singla, 2022 ). The entomopathogenic fungi B. bassiana and Metarhizium anisopliae have shown greater virulence against a wide range of medical and agricultural insect pests ( Contreras et al, 2014 ; Gebremariam et al, 2021 ; Wang et al, 2021 ; Bapfubusa Niyibizi et al, 2023 ; Sharma et al, 2023 ; Swathy et al, 2023 ; Vivekanandhan et al, 2023 ). The cuticle-degrading enzyme chitinase, derived from the entomopathogenic fungi B. bassiana , exhibited remarkable insecticidal activity within 5 days against larvae of B. dorsalis ( Ullah et al, 2023 ).…”

Survival dynamics of stick insect and the impact of environmental factors on natural fungal infection during the rainy season

“…Entomopathogenic fungi have emerged as highly promising alternative biocontrol agents to chemical insecticides ( Erler and Ates, 2015 ; Perumal et al, 2023 ; Vivekanandhan et al, 2023 ; Perumal et al, 2024a , b ). Metarhizium and Beauveria species are two main generalist entomopathogenic fungi widely employed in pest control across various insect species, including agricultural pests ( Mascarin and Jaronski, 2016 ; Peng et al, 2021 ; Krutmuang et al, 2023 ; Vivekanandhan et al, 2024 ; Perumal et al, 2024a , b ).…”