Abstract

Purple blotch of garlic caused by Alternaria porri is recognized as a prominent diseases posing threat to garlic cultivation throughout the world including Bangladesh. The experiments were conducted to determine the prevalence of purple blotch disease on garlic varieties in field condition, to test the pathogenicity of isolated causal organism and to find out the suitable management options of the disease. Eight garlic varieties viz. BAU Rashun-1, BAU Rashun-2, BARI Rashun-1, BARI Rashun-2, BARI Rashun-3, BARI Rashun-4, Local Deshi and Local Indian were explored in prevalence study and nine management option comprising a bio-agent Trichoderma harzianum (T₁), five botanicals viz.  Lantana camara (T₂), Spilanthes paniculata (T₃), Ocimum sanctum (T₄), Raphanas raphanistrum (T₅) and Azadirachta indica (T₆), two fungicides Mancozeb 80% WP (T₇) and Sulcox 50% WP (T₈) and, an untreated control (T₉) were explored in the experiments. BARI Rashun-3 showed the highest disease incidence (40.00%) and severity (92.00%) of purple blotch disease. Isolation, identification of pathogen and pathogenicity test was carried out as well. In case of management, all botanicals and bio-agent were tested significantly beneficial in lessening the disease incidence and severity of purple blotch disease. The results revealed that Lantana camara (T₂) was found most effective for minimizing the disease incidence (26.67, 26.67 and 33.33%) at 30, 45 and 60 DAS, respectively while maximum disease incidence was recorded in control (T₉) (86.67, 96.67 and 100.00%). T₂ also reduced disease severity at 30 DAS (11.00%) whereas, at 45 DAS (18.67%) and 60 DAS (19.33%) T₁ performed well against the disease.