Evaluation of host plant resistance against the rice leaf folder (Cnaphalocrosis medinalis) and yellow stem borer (Scirpophaga incertulus) through genotypic screening of rice

Insect pests pose a significant threat to crop yield and production worldwide. The yellow stem borer (Scirpophaga incertulus Walker) and rice leaf folder (Cnaphalocrosismedinalis Guenee) are the important pests infesting rice plants. These insects are highly susceptible in the rice-growing region, resulting in a substantial decline in productivity and economic losses. Thus, pest screening is necessary to evaluate the damage caused by different rice genotypes/varieties and investigate host plant resistance against those devastating insects as a pest-mitigating strategy. For this, 20 rice accessions (15 genotypes & 5 cultivars) were screened against C. medinalis and S. incertulus under natural field conditions in a rice research farm at G.P. Koirala College of Agriculture & Research Center, Gothgaun, Morang, Nepal, during summer 2022. The field damage scoring was done to determine the pest infestation level (counting dead hearts for yellow stem borer and damaged/folded leaves for rice leaf folder) in 50, 60, 70, 80, 90, and 100 days after transplanting (DAT), and scaling was given based on the percentage of leaf damage/infestation. The evaluation indicated that rice genotype IR92521-172-5-1-1 showed a high level of resistance among all other accessions against the rice leaf folder (about 6.11% damage). Similarly, the rice variety Radha-13 resulted lower infestation (about 0.547% dead heart) than other accessions against yellow stem borer. Moreover, the rice accessions Subarna Sub-1 and NR2188-13-5-2-5-1 were moderately resistant to rice leaf folder and yellow stem borer, with leaf/plant damage of (14.61%) & (9.954%) respectively. Conclusively, most of the rice accessions evaluated had better plant resistance against those two pests, i.e., rice leaf folder & yellow stem borer.