Vol. 9, Issue 3 (2020)

Author(s):
SH Peerzada, HS Viswanath and KA Bhat

Abstract:
Late blight is one of the most destructive diseases causing severe yield losses of potato in Kashmir valley. So, In the present study, four different protectant fungicides (mancozeb 75 WP, chlorothalonil 75 WP propineb 70 WP) were evaluated at field level at three different concentrations (1.5%, 2% and 2.5%) by spraying at weekly intervals starting from symptom exhibition to the ten days before dehaulming stage during cropping seasons 2016 and 2017. With this study, it was found that all the fungicides (mancozeb, propineb and chlorothalonil) were equally superior to control (water spray) in reducing the blight incidence from 75.55 to 31.03 per cent. There existed a significant interaction between fungicides and their concentrations. All the three test fungicides at C1-C3 concentration reduced the disease incidence to 24.44-51.17 per cent from 75.55 per cent observed in water sprayed check. Mancozeb 75WP was highly effective in reducing the late blight disease with a least mean disease intensity, incidence and area under disease progress curve(A value) values of 15.07,31.10 and 82.48% respectively at all the test concentrations followed by propineb 70WP and chlorothalonil 75WP, whereas highest amount of disease development was recorded in control (water spray), with mean disease intensity, incidence and AUDPC values of 55.39%, 77.77% and 292.34% respectively during the season 2016. Similar trend of results were obtained during the season 2017 where mancozeb showed highest efficacy against late blight disease with mean disease intensity, incidence and AUDPC values of 15.74%, 31.03% and 84.83% followed by propineb 70 WP and chlorothalonil 75 WP compared to control (water spray) where disease intensity, incidence and AUDPC values were recorded as 53.24%, 75.55% and 293.24% respectively. Apart from the disease control, highest tuber yield and marketable (grade A&B) tuber percent were also recorded in the treatment with mancozeb followed by propineb 70WP and chlorothalonil 75WP, whereas lowest tuber yield and unmarketable tubers (grade C) were recorded in control (water spray) treatment during cropping seasons of 2016 and 2017.