author(s)
Robin Singh, Dilbagh Ahlawat and Kanika Nagpal

abstract
A field experiment was conducted to evaluate the effect of nitrogen and potash levels on the incidence of sugarcane top borer under Haryana conditions at the farm of Regional Research Station CCS HAU Uchani, Karnal during 2015-16. The experiment was laid out in split-split plot design with three differently maturing varieties viz., Co 0238, CoH 119 and CoH 150 as main plot, three doses of nitrogen viz., 150, 200 and 250 kilogram per hectare (kg/ha) as sub plot and two doses of potash viz., 0 and 50 kg/ha as sub-sub plot. The mean per cent incidence (%) of top borer recorded in July, August and September, 2015 was highest (9.11, 11.78 and 13.56, respectively) in Co 0238 followed by CoH 150 (7.33, 10.00 and 12.44, respectively) while, lowest incidence was (6.22, 7.56 and 10.67, respectively) in CoH 119. With respect to nitrogen application, the maximum mean per cent incidence (9.11, 11.56 and 14.44, respectively) in July, August and September, 2015 of top borer was recorded at 250 kg N/ha and the minimum (5.78, 7.78 and 9.56, respectively) at 150 kg N/ha. Application of potassium significantly reduced the top borer infestation with mean per cent incidence lower at 50 kg K₂O/ha (6.52, 9.04 and 10.52, respectively) in July, August and September, 2015 compared to control i.e., no application of potassium (8.59, 10.52 and 13.93, respectively). Hence, there is need to optimize nutrient and their balanced application to reduce the topborer incidence in sugarcane. Nitrogen fertilizer (200 kg N/ha) combined with potassium application produced highest cane yield, number of millable canes and commercial cane sugar by reducing the top borer incidence.