Abstract
A damage level-based Action Threshold (AT) level was determined for the sugarcane internode borer (INB)Chilo sacchariphagus indicus (Kapur) in Sri Lanka. Two experiments, one in 1997/ 1998 as early planting crop and the other in 1999/2000 as late planting crop were conducted with the variety Co 775 at Uda Walawe, Sri Lanka. The experiments included maintenance of Chlorpyrifos-sprayed and control plots to measure cane yield at different infestation levels of INB. Cane yield losses were determined at different damage levels. Variation of damage levels and cane yields was tested by ANOVA. Effect of INB on cane yield was studied by correlation and regression analysis and the regression equations were used to estimate net revenue for determining AT. The highest damage level in the early- planted crops selected for chlorpyrifos spraying was 35 percent bored internodes and that for control was 33%. In the late-planted crop, the highest damage levels for the plots selected for chlorpyrifos spraying and control were 40% and 43%, respectively. The cane yield losses of the insecticide-sprayed and unsprayed plots at harvest were 2.6% and 26.8% respectively, in the early planted crop and those for late planted crop were 3.1% and 32.7%. There was a strong negative correlation between cane yield and damage level. The AT for the internode borer was found to be 13 - 15% bored internodes.
Published Version
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