CONTROL OF PURPLE BLOTCH COMPLEX OF ONION THROUGH FERTILIZER AND FUNGICIDE APPLICATION

Abstract

An investigation was carried out in the seed health laboratory of the Department of Plant Pathology and in the farm of Sher-e-Bangla Agricultural University to evaluate the effect of selected fungicides and micronutrients against Alternaria porri and Stemphylium vesicarium causing purple blotch complex of onion. Four chemical fungicides, viz. Rovral 50 WP, Dithane M-45, Ridomil gold and Cupravit and micronutrients (ZnSO + Borax) were assayed alone and in combination in the investigation. In in vitro test Rovral 50 WP (0.2%) showed the promising result against mycelial growth of Alternaria porri and Stemphylium vesicarium that reduced the mycelial growth by 69.00% and 76.56% respectively followed by Dithane M-45. In the field experiment, the fungicides were tested alone and in combination with micronutrients (ZnSO 4 + Borax), comprised with ten treatments. Among those treatments, the application of chemical fungicide in combination with micronutrients always performed better than the application of chemical fungicide alone in controlling purple blotch complex of onion. Rovral 50 WP (0.2%) + Micronutrients reduced the disease incidence (% Leaf infection) and disease severity (% Leaf area diseased)

4 by 20.92% and 44.88%, respectively followed by Rovral 50 WP (0.2%) alone, Dithane M-45 (0.45%) + Micronutrients and Dithane M-45 (0.45%) alone. The bulb yield and yield contributing characters viz. plant height, plant dry matter, root length and weight were found significantly higher in case of application of Rovral 50 WP (0.2%) + Micronutrients where yield was increased by 36.88% over control.