MANAGEMENT OF PURPLE BLOTCH COMPLEX OF ONION (Allium cepa) FOR SEED PRODUCTION

Abstract

The study was carried out in the central farm of Sher-e-Bangla Agricultural University and in the Seed Health Laboratory, Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka with a view to evaluate the efficacy of different treatments against Alternaria porri and Stemphylium vesicarium causing purple blotch complex of onion for seed production. The onion variety, ‘Taherpuri’ was used in the experiment. The foliar spray experiment was laid out in a RCBD with three replications. Eight treatments, Viz. T 0 = Control (No spraying); T 1 = Foliar spraying with Alamanda leaf extract 1:2 (W/V); T 2 = Foliar spraying with Neem leaf extract 1:2 (W/V); T 3 = Foliar spraying with Score 250 EC @ 0.2%; T 4 = Foliar spraying with Rovral 50 WP @ 0.2%; T 5 = Foliar spraying with Dithane M-45 @ 0.45%; T 6 = Foliar spraying with Tricost 1 % WP- @ 0.3% (Trichoderma harzianum); T 7 = Foliar spraying with Micronutrients (ZnS0 4 + Borax) were explored in the experiments. A significant variations were observed in respect of disease incidence and severity of purple blotch complex, seed yield, yield contributing characters, seed germination and prevalence of seed borne pathogens of harvested seeds as influenced by the treatment of different selected spray. The highest seed yield 707.45 kg/ha was obtained in case of treatment T 4 where foliar spraying were applied with Rovral 50 WP @ 0.2%. The lowest percent leaf infection, percent disease index (PDI-leaf), percent infected seed stalk, percent Stalk Area Disease (%SAD) were recorded in foliar spray with Rovral 50 WP followed by Score 250 EC. The highest seed germination by 93.5 % and the lowest prevalence of Alternaria porri by 0.25 % & Stemphylium vesicarium by 0.75 % and also total pathogenic infection by 8.5 % were recorded on harvested onion seed from Rovral 50 WP treated experimental plot followed by Score 250 EC.