The response to flooding of two overwintering rice stem borers likely accounts for their changing impacts

Abstract

The rice striped stem borer (SSB), Chilo suppressalis Walker, and the rice yellow stem borer (YSB), Scirpophaga incertulas Walker, are two of the most damaging pests of rice plant, whose relative crop damage has changed in recent years. Here, we carried out experiments and surveys to understand the potential impact of field flooding on populations of these species. YSB had a consistently higher mortality rate than SSB in overwintering populations. We show that SSB survived under submersion better than YSB, crawled more strongly than YSB, and escaped more effectively from a waterlogged environment than YSB. These differences may relate partly to the longer abdominal prolegs and thoracic legs of SSB than YSB. These factors likely explain why YSB has a higher mortality rate than SSB in overwintering populations and why the relative importance of YSB is declining in some areas. In addition, the flooding method provides an effective cultural practice for some crops. Our results uncover the reasons why flooding practice is more effective for YSB than SSB. The results also point to an effective control measure for YSB.