Evaluation of lufenuron, diflubenzuron and novaluron for their lethal concentrations/doses (LC50/LD50) and chitin inhibition against Spodoptera litura

studies on bioassay showed that LC50 (LD50) values of lufenuron, diflubenzuron and novaluron against third instar larvae of S. litura by topical method were 44.073 ppm (2.93 μg/g), 90.048 ppm (6.00 μg/g) and 59.885 ppm (3.90 μg/g), while the values against fifth instar larvae were 92.646 ppm (6.17 μg/g), 177.500 ppm (11.80 μg/g) and 105.327 ppm (7.02 μg/g), respectively. Similarly the values by ingestion method against third instar were 62.581 ppm (104 μg/g), 75.828 ppm (126 μg/g) and 74.731 ppm (124 μg/g), while the values against fifth instar larvae were 117.669 ppm (11.70 μg/g), 129.024 ppm (12.90 μg/g) and 124.552 ppm (12.40 μg/g), respectively. The per cent reduction of chitin in third instar larvae of S. litura due to lufenuron, diflubenzuron and novaluron at their median lethal concentrations (LC50) in ingestion method was 21.35, 18.11 and 12.97, whereas in fifth instar it was 28.27, 24.96 and 13.34, respectively. But the per cent reduction of chitin in third instar larvae of S. litura due to lufenuron, diflubenzuron and novaluron at their LC50 values in topical method was 26.24, 22.00 and 15.55, whereas in fifth instar it was 29.20, 26.04 and 14.58, respectively.