Resistance to Diamide Insecticides in Stem Borers of Rice in Bangladesh

The study was conducted from September 2019 to December 2020 to know the efficacy of the diamide products, namely Virtako 40 WG (Chlorantraniliprole + Thiamethoxam) and Coragen 18.5 SC (Chlorantraniliprole) against rice yellow stem borer (Scirpophaga incertulas) and dark headed stem borer (Chilo suppressalis). Larvae of the stem borers were collected from four locations of Bangladesh, and then the diamide products with the concentrations of 0.1, 0.5, 2, 10, 50 and 200 ppm were applied along with untreated control to know the mortality of the larvae at 96 hours after treatments. Diamide products showed differing mortality effects on the larvae based on different concentrations. After the application of Coragen 18.5 SC, the highest rate of mortality of larvae of S. incertulas and C. suppressalis at the four locations were 55.0 to 68.8% and 51.4 to 59.5%, respectively with the concentration of 200 ppm. In Virtako 40 WG, also the concentration of 200 ppm showed the highest mortality of the larvae of the four locations ranging from 60.6& to 71.3% in S. incertulas and 59.8 to 70.9% in C. suppressalis . The LC₉₅ value of the Coragen 18.5 SC ranged from 337.2 to 494.6 ppm for S. incertulas and 435.2 to 557.0 ppm for C. suppressalis. LC₉₅ value of Virtako 40 WG ranged from 312.1 to 488.1 ppm for S. incertulas and 405.6 to 514.0 ppm for C. suppressalis.