Pheromone characterization and behavioral responses of the local rice yellow stem borer (Scirpophaga Incertulas) to different Sri Lankan rice varieties

Abstract

The Rice Yellow Stem Borer (YSB), Scirpophaga incertulas (Lepidoptera: Crambidae), is a major pest that poses significant yield losses in Sri Lankan paddy cultivation. Synthetic chemical insecticides are the primary control method. However, their long-term effectiveness is limited due to negative impacts on biodiversity and risk to human health. This study aims to characterize the pheromone components of the local YSB population and assess their behavioral responses to different Sri Lankan rice varieties. Pheromone components were collected from female YSB using dynamic headspace collection (30 individuals per replicate) and solvent extraction (15 individuals per replicate). A varietal preference test was conducted using a dual choice olfactometer for eight rice varieties: BG 366, AT 311, BG 257, AT 362, BG 251, AT 313, BG 360 and BG 377. The collected volatile compounds were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). The GC-MS analysis identified (Z)-11 Hexadecenal as a major sex pheromone compound in YSB. The varietal preference test shows significant differences (p = 0.001) among the rice varieties. Notably, AT 313 is the most attractive rice variety (13.2 ± 0.33), and BG 251 is the least attractive rice variety (3.8 ± 0.22) to the female YSB. S. incertulas most prefers to damage paddy cultivation after the pre-booting stage (early panicle initiation). The optimum laboratory rearing conditions for S. incertulas were determined as 26 ± 2 0C temperature, 75 ± 5% relative humidity, and a 10-12 hours light: 12-14 hours dark cycle. Further studies are necessary regarding laboratory bioassays and field evaluations to develop a sustainable and effective semiochemical-based pest management strategy (pheromone trap) to manage the rice yellow stem borer more effectively.