Determining Optimum Number of Pesticide Applications and Economic Injury Level for Leaf Folder (Cnaphalocrocis medinalis) on Rice (Oryza sativa)

The leaf folder incidence on Pusa Sugandh 3 rice ranged from 1.2–20.5% with the highest tnfestation between 45–55 days after transplanting (DAT). Differential applications with endosulfan (35 EC) were carried out to generate variability in pest infestation in different treatments. Yield-infestation relationships established with linear, semi ioge^x, quadratic, power and exponential functions were observed to be negative from 45–65 DAT but these were substantive only at 55 DAT (R²= 0.638–0.743). Two sprays with endosulfan at 50 and 70 DAT proved to be optimum against the pest by preventing yield loss to the tune of 26.2% and had highest benefit-cost ratio. Economic injury levels (EILs) with different empirical relations ranged between 1.0–11.5% at 55 DAT and 1.1–18.7% at 65 DAT with mean value of 6.5 and 9.8%, respectively.