Yadav_2026_Sci.Rep_16_

Environmental issues associated with the excessive use of chemical substances have received increasing attention globally, particularly regarding their effects on non-target/beneficial insects such as pollinators. To overcome such drawbacks, alternative control methods are being increasingly evaluated. A study was conducted to assess the effectiveness of two Indian biopesticidal isolates against the mustard aphid, Lipaphis erysimi, on rapeseed crops and to investigate their potential risks to the pollinator honeybee, Apis cerana. Laboratory bioassays showed that Beauveria bassiana AS-4220 was the most effective material against L. erysimi after 24 h (LC(50) = 95.5 ppm); however, neem seed oil was the most toxic to A. cerana after the same time interval (LC(50) = 185.4 ppm). The highest reduction in the aphid population under field conditions was observed with B. bassiana AS-4220 at 3 x 10(8) spores mL(- 1) ten days after field treatment (71.9%), followed by B. bassiana AS-4220 at 2 x 10(8) spores mL(-1) ten days after field treatment (70.7%). The highest PT (persistent toxicity index) and RPT (relative persistent toxicity) values were observed for B. bassiana at 3 x 10(8) spores mL(- 1) (799.98 and 1.06, respectively). The benefit: cost ratio among the treatments was highest for B. bassiana at 3 x 10(8) spores mL(- 1) (4.90:1). However, the highest honeybee mortality was observed following treatment with neem seed oil at 3 mL L(- 1) and B. bassiana at 3 x 10(8) spores mL(- 1) ten days of treatment (100%). No significant inhibition of acetylcholinesterase (AChE) activity was observed in honeybees 24 h after treatment. The study demonstrates that entomopathogenic fungi effectively control L. erysimi while posing some risk to A. cerana, particularly at higher concentrations, necessitating careful timing of application . Therefore, these treatments may be used to manage L. erysimi in rapeseed crops while minimizing effects on A. cerana bees, provided that application is scheduled during periods of low foraging activity.