Determination of multiple-species economic injury levels for rice insect pests

Abstract

Yield loss to damage functions were established to determine multiple-pest economic injury levels (EILs) on Pusa Basmati 1 rice (Oryza sativa L.) at different crop growth stages through field and pot experiments in 2009 and 2010. The yield loss to damage functions were derived for two-pest combinations of leaf folder, Cnaphalocrocis medinalis Guenée, and stem borers, Scirpophaga incertulas (Walker) and Sesamia inferens (Walker), at reproductive crop stage during 2009 and for leaf folder and planthoppers, Nilaparvata lugens (Stål.) and Sogatella furcifera Horvath, at vegetative crop stage, and planthoppers and stem borers at reproductive stage during 2010. Single-species as well as multi-species EILs were determined. Across experiments, single-species EILs of leaf folder and stem borer ranged from 2.9e6.4% folded leaves and 1.9e3.0% whiteheads, respectively, while that of planthoppers varied between 5.5 and 7.3 hoppers per hill. Iso-loss equations, based on yield loss to damage functions, depicted various two-pest incidence combinations which resulted in economic damage. These joint incidence combinations showed that, although each pest was below its EIL, the combination of both pests inflicted economic damage. The multi-pest EILs can be useful to monitor simultaneous occurrence of two-pest species thereby helping to prevent yield losses.