Yield losses in resistant and susceptible varieties of rice in Nigeria due toChilo zacconiusand other stem borers

Abstract

Abstract In a screenhouse experiment, rice plants of eight varieties were artificially infested at the early tillering and booting stages with African striped borer, Chilo zacconius Bleszynski, one Iarva per tiller. In the mature plants there was found to be a reduction in height and an increase in tiller number among susceptible varieties and, to a lesser extent, among the resistant varieties. Additional tillers gave rise to panicles which had not matured by the time the uninfested tillers were harvested; as a result there was a significant reduction in grain yield and grain weight among the susceptible varieties. In a separate field trial some plots were protected with 3% carbofuran at 13 kg/ha. Infestation by the stem borers Maliarpha separatella Ragonot, C. zacconius and Sesamia spp. was consistently higher in protected susceptible varieties than in unprotected and protected resistant varieties. Yields were about twice as high in protected as in unprotected plots of susceptible varieties, but there wa...