Influence of sowing time on development of cercospora leaf spot and yellow mosaic diseases of urdbean (Vigna mungo)*

Abstract

A field experiment was conducted during rainy season of2003 and 2004 to study the influence oftime ofsowing on development of cercospora leaf spot and yellow-mosaic and grain yield of 2 urdbean varieties, namely 'Barabanki local' and 'KU 99' in a factorial randomized block design at the Institute, New Delhi. The intensities of cercospora leaf spot and yellow mosaic on variety 'Barabanki local' were higher in comparison to the 'KU 99' at all the dates of sowing. Early sown crop, ie on 1 July showed more intensity of cercospora leaf spot and yellow mosaic and produced low yield. The crop sown on 15 July gave significantly higher grain yield ofboth the varieties over other sowing dates and favoured moderate disease development. After that disease intensities as well as yields were declined at later dates of sowing. Correlations were established between weather factors and disease development. Temperature was positively whereas relative humidity and sunshine hours were negatively correlated with disease development in field. Depending on the amount of rainfall, its correlation differed from positive to negative in different years of experin1ent. maximum temperature, rainfall and sunshine hours accounted 83.7 -- 99.6% variation in diseases in multiple regression analysis.