At the tillering stage, larvae of the yellow stem borer (YSB) Scirpophaga incertulas (Walker) cause deadhearts after about 1 wk of feeding inside the leaf sheath. At the preheading stage, larvae cause whiteheads after about 4 d of feeding inside the panicle stem. Cultivars that cause high early mortality of YSB larvae are good sources of resistance for breeding programs because many larvae will be killed before they have done sufficient feeding to cause deadheart or whitehead. In this study, we compared early larval mortality of YSB on four indica cultivars.
IR36, IR40, IR62, and IR72 rice seedlings were transplanted in a screenhouse at the rate of two seedlings hill-1. One month after transplanting, hills were transferred into 13-cm-diam pots (one hill pot-1) and caged in a greenhouse. There were four replicates for each cultivar. One egg mass (130-135 eggs; approximately 5 × 4 mm) was placed on a hill in each cage. Three days after egg hatching, plants were uprooted from pots and stored at ambient temperature for 0-24 h before being dissected under a binocular microscope. Data were subjected to ANOVA and means were compared by LSD.