Field evaluation of rice accessions against leaf folder complex

摘要

Rice (Oryza sativa L.), is the most important crop, cultivated extensively in the most diverse ecosystems of tropical and subtropical regions of the world. Eight species of pyralid moths, whose larvae roll or fold leaves of graminaceous plants, comprise the leaf folder complex. They are Cnaphalocrocis medinalis (Guenee), Marasmia patnalis Bradley, M. (=Susumia) exigua (Butler), M. bilinealis Hampson, M. ruralis (Walker), M. suspicalis (Walker), M. trapezalis (Guenee), and M. venilialis (Guenee). Currently, only three species, viz., C. medinalis, M. patnalis, and M. exigua, have attained pest status in rice. Among them, C. medinalis traditionally has been accepted as a sole leaf folder pest in the lowland rice fields of Asia (Babyrani et al., 2007).The rice leaf folder complex, previously considered as a minor pest, has gained major pest status and caused considerable yield loss (Singh et al., 2003). In certain cases it has been recorded to cause 63 to 80 per cent loss in rice yields (Rajendran etal, 1986). Use of host plant resistance acts as a digestibility inhibitor in the leaf folder. It weakens the immunity system and prevents the development of resistance in the pest. In many cases, host plant resistancewould provide effective control of leaf folder with less hazards and safe to non-target organisms. There is an urgent need for minimizing the use of chemical pesticides in the management of insect pests. Keeping these points in view, an attempt has beenmade to evaluate the rice accessions against leaf folder complex.