Early-stage management of brown planthopper (Nilaparvata lugens stål) through seed treatment: A preventive strategy in rice cultivation

Early infestation by brown planthopper (BPH) is common in rice ecosystems. Foliar application of insecticides is normally practised but adversely affects natural enemies and the environment. This study evaluated the effects of insecticidal seed treatments using a randomised design with three replications at the Bangladesh Rice Research Institute from August 2024 to March 2025. Germination percentage varied significantly among treatments, with the highest germination in the untreated control (91.3%), while the lowest in cartap (65.0%). Neonicotinoid seed treatments maintained superior germination (>87%) and promoted seedling vigour. Seedling damage was highest in the untreated control (>81%) and cartap (>54%), whereas imidacloprid (9.00-12.33%) and thiamethoxam (2.67-5.33%) provided strong protection with < 12% damage under both no-choice and choice tests. The dynamics of the BPH population further confirmed consistent suppression by imidacloprid and thiamethoxam across 28 days after sowing, while the control plots sustained the highest densities. Sweep collections showed higher pest abundance in untreated and cartap plots, whereas imidacloprid- and thiamethoxam-treated plots recorded significantly lower populations from the seedbed. Natural enemy abundance also varied, with untreated and isoprocarb plots harbouring more green mirid bugs, while spider populations were highest under imidacloprid treatment, suggesting relatively lower non-target impacts on natural enemies among the treatments. Overall, imidacloprid and thiamethoxam were most effective in enhancing seedling vigour and suppressing BPH, while maintaining a relatively higher field abundance of spiders compared with other treatments. These findings highlight the potential of seed treatments for early-stage BPH management, reducing reliance on foliar sprays.