Onion suffers from many diseases and among them purple blotch complex is devastating for both bulb and seed production in Bangladesh. To formulate an integrated approach for its management, different IPM components viz. three fungicides viz. Rovral 50 WP (Iprodione), Dithan M-45 (Mancozeb) and Score 250 EC (Difenconazol); two botanicals viz. Alamanda leaf extract (Allamanda cathartica) and Neem leaf extracts (Azadiracta indica); four soil amendments viz. Poultry manure, bioagent, saw dusts and micronutrients (Zn @ 0.45/L +B @ 2.5g/L) were evaluated under field condition. The experiment was conducted at the farm of Sher-e-Bangla Agricultural University, Dhaka, during 2011-2012. Pathogeninicity test indicated that Alternaria porri and Stemphylium vesicarium were the pathogens where S. vesicarium initiated the infection and A. porri facilitated the subsequent infection and made a complex form of disease. Among the chemical fungicides, Score 250 EC was found promising followed by Rovral 50 WP against purple blotch complex in terms of reduction of disease incidence and severity ultimately contributing to increased yield (134% and 129%, respectively) over control. Among botanicals, Alamanda leaf extract produced better result compared to neem leaf extract (99.6% and 67.6% respectively). In terms of increasing yield, poultry manure showed better performance (72.3%) followed by micronutrient (69.5%) and bioagent (58.2%). Bangladesh J. Agri. 2019-2021, 44-46: 31-44

Onion (Allium cepa) is one of the most important spices in Bangladesh. It suffers from various diseases from seedbed to field. Purple blotch (Alternaria porri) and white blotch (Stemphylium vesicarium) simultaneously attack the crop, causing a purple blotch complex. To assess locally available onion cultivars for response to purple blotch complex and yield performance, a three-year experiment was conducted in the net house and research field of Sher-e-Bangla Agricultural University, Dhaka, during the winter of 2010-11, 2011-2012 and 2012-2013. Fourteen onion cultivars, namely BARI Piaz-1, BARI Piaz-2, BARI Piaz-3, BARI Piaz-4, BARI Piaz-5, Taherpuri, Indian hybrid, Lal Teer onion seed, Masud onion seed, Thakurgoan local, Faridpur local, Manikgong local, Indian big and Indian small were used in the experiment. Among the evaluated cultivars, BARI Piaz-3 showed the lowest disease incidence and severity and the maximum bulb yield, followed by BARI Piaz-2 and Indian big. The disease incidence, severity, and yield for BARI Piaz-3 were 54.45-36.33%, 5.75-12.01%, and 10.97-13.89 t/ha, while the corresponding values for BARI Piaz-2 were 41.49, 44.01, and 7.28-10.79 t/ha, respectively. In contrast, Indian big had disease incidence, severity, and yield values of 36.52-58.79%, 15.43-22.96%, and 8.41-10.60 t/ha, respectively. Therefore, the cultivar BARI Piaz -3 and 2 may be recommended for extension of cultivation.Ann. Bangladesh Agric. (2021) 25 (2) : 37-46