Influence of weather parameters on progress of Alternariaster leaf blight of sunflower

Abstract

One of the major disease in sunflower i.e., blight caused by Alternariaster helianthi can infect all growth stages and causes severe losses. It is seed borne pathogen and causes heavy defoliation under congenial climate and yield losses estimated from 20 to 80%. A field study was conducted on impact of weather parameters on Alternariaster leaf spot of sunflower during kharif, for four years i.e., 2013-14, 2014-15, 2015-16, 2016-17 at RARS, Nandyal with four different dates of sowing, using two cultivars KBSH-44 and morden and the disease was recorded at weekly interval. Influence of weather parameters on PDI corresponding to the same week or previous week were observed and the conditions like moderate temperatures, relative humidity (RH-I>80% and more RH-II), more rainfall and crop age have more influence on disease development. Correlation coefficient values for combined data of four years indicated that PDI was negatively correlated with Tmax, Tmin, rainfall and wind velocity on both cultivars and positive with RH-I and plant age. Regression equations in all the individual experimental years and in total indicated that Tmin, Tmax, RH-I, rainfall and age significantly influence the disease progress. Apart from these factors, dew point, spore load, sunshine hours and micro climate may also affect disease development. Hence, disease progression mainly depends on weather conditions. More AUDPC values observed in later date of sowings than early date of sowings.