B.P. Sharma, H.B. Khatri and S.P. Dhital

DOI

ABSTRACT

An experiment was conducted to optimize the application of fungicides for late blight control under natural epiphytotic conditions at Khumaltar during autumn season of 2004 and 2005. Most commonly used metalaxyl containing fungicide Krilaxyl (Metalaxyl 8% + Mancozeb 64%) was tested for its rational use with varying number of sprays at 10 days intervals starting from 25 days after planting (DAP) up to the 75 DAP. Disease severity on foliage was recorded at 30, 40,50,60,70, and 80 DAP and tuber infection was recorded based on visual observation just after harvest. At 80 DAP, highest remained green leaf (RGL) area was found (69.4 %) in six times sprayed plot followed by 5, 4, 3, 2 and single spray plots 62.8%, 55.3%, 50.9%, 33.8% and 23.1% respectively. Tuber blight was highest in untreated check plot (6.6%) and incidence was found decreasing as the number of sprays increased. Tuber yield was also increased ranging 1.5 to 9.6 t/ha as per the number of sprays increased. Total cost of fungicide and application as per treatment were Rs. 3, 800 to 31,170 per hectare. When cost per treatment was compared with the additional return due to treatment, highest cost benefit (C:B) ratio (1:2.6) was obtained from three sprays. C:B ratio was found minimum in six sprays (1:1.5). Cost benefit ratio was better (1:2.1) in single spray of Krinoxyl at 25 DAP as compared to six times sprays.