Variability in the Biology of the yellow Stem Borer Scirpophaga incertulas from the Philippines

Abstract

Six local strains of the yellow stem borer, Scirpophaga incertulas, were collected from the field and reared in the susceptible variety IR62 at the same conditions in the greenhouse. Development time of the larvae from hatching to emergence was noted in the first to third generations (F 1-F3). Sex ratios were recorded from the fust three and twelth generations. Significant difference in development among populations was observed although this varied from generation to generation presumably due to temperature effects in the greenhouse. However, no differences in development time between the tvo sexes, and no sex by population interaction were observed in all three generations in culture. It was concluded that sex was not a factor attributable to variations hetween populations. Primary sex ratios among the populations did not deviate from 1:1 although succeeding generations showed some minor variations. When five populations were allowed to develop in nine rice hosts, variation in pupal weights and development between the populations among different rice hosts was observed. Variation between the two sexes was not observed for pupal weights and developmental period. The host was observed to be a major factor for the differences in development among populations.