Stem borers in grain sorghum: I. Injury patterns with time after crop emergence

Abstract

The progression of different categories of plant damage caused by Busseola fusca (Fuller) and Chilo partellus (Swinhoe) with time after crop emergence was determined through regular sampling from nine sorghum plantings in each of three seasons. Tillers were more prone to ‘dead heart’ and damage to the lower stems than main culms while main culms suffered more damage to the peduncles. Whorl damage reached a maximum six weeks after crop emergence and was to some extent indicative of the eventual incidence of ‘dead heart’ but not of the extent of stem and peduncle injury. The number of stems damaged always exceeded the number of stems infested, irrespective of crop growth stage or levels of infestation. Internal stem injury continued to increase after physiological maturity of the plants. The significance of the results in the predictive estimation of crop losses is discussed.