Mango stem-end rot (Lasiodiplodia theobromae) is a devastating post-harvest disease that can cause substantial fruit losses during storage and transit. Effective disease management relies on an accurate understanding of its prevalence. This study assessed SER incidence and severity across major mango-growing districts of Bangladesh and investigated the potential of fungal antagonists as biological alternatives to chemical fungicides. Therefore, SER assessments were carried out on 1,600 mango fruits sampled from 16 orchards spanning Chapainawabganj, Rajshahi, Rangpur, and Natore districts. At the district level, SER incidence fluctuated between 13% and 19%, while corresponding severity values ranged from 8% to 13%. Trichoderma harzianum and three isolates of Clonostachys rosea were subsequently screened against L. theobromae through dual culture confrontation and cell-free culture filtration assays. Among the agents evaluated, T. harzianum filtrates exhibited the strongest anti-fungal activity, achieving complete suppression of L. theobromae under both in vitro and in vivo conditions while preserving acceptable fruit quality. These findings present a viable and environmentally responsible biocontrol
strategy for managing postharvest SER in mango. To the best of the authors’ knowledge, this study first reported the biocontrol effect of T. harzianum metabolites on postharvest mango stem-end rot and maintained the quality of mango fruit.