Harnessing the potential of indigenous entomopathogenic fungi isolated from the soils of Tamil Nadu, India, for the management of the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae)

Abstract Background Cotton ( Gossypium spp.) is an important commercial crop being cultivated worldwide, but its production is hampered by many insect pests. The cotton aphid, Aphis gossypii Glover, is a key pest with increasing resistance to chemical insecticides. To explore eco-friendly management alternatives, this study evaluates the pathogenic potential of indigenous entomopathogenic fungi, isolated from cotton-growing regions of Tamil Nadu, India, via the ‘ Galleria bait method’. Results Five entomopathogenic fungi were isolated and identified as Beauveria spp. based on cultural and morphological features. Molecular characterization by amplification of internal transcribed spacer-ribosomal DNA (ITS-rDNA) regions confirmed the isolates as B. bassiana . Among them, isolate B5 (accession number: PP503009) exhibited the highest virulence, inducing 96.67% mortality at 7 days after treatment (DAT) with the concentration of 1 × 10 8 spores·mL −1 . The median lethal concentration (LC 50 ) and median lethal time (LT 50 ) values were 9.75 × 10 4 spores·mL −1 at 7 DAT and 72.31 h at 1 × 10 8 spores·mL −1 , respectively. Scanning electron microscopy (SEM) images highlighted a progression of infection stages of B5, including spore attachment (24 h post infection (hpi)), hyphal penetration (48 hpi), and conidiogenesis (72 hpi). Conclusion The isolate B5 proved to be a promising candidate for the development of biopesticides for sustainable cotton aphid management in Tamil Nadu, India.