Infestation and injury levels of stem borers in relation to yield potential of grain sorghum

摘要

The infestation patterns of the stem borer speciesBusseola fusca(Fuller) andChilo partellus(Swinhoe) and the effect on plant yield, tiller number, plant height, peduncle length and internal damage were determined under conditions of differential nitrogen fertilization and soil moisture. Planting date had a significant effect on the Infestation pressure and selective oviposition was observed between the different categories of irrigation and fertilization. Irrigated plants suffered higher yield losses than dry-land plants. Fertilizer application led to an increase in the number of tillers per main stem but no compensatory growth resulted from borer attack, irrespective of infestation pressure. Borer damage significantly influenced plant height and peduncle length. Under severe infestation pressure, dry-land plants suffered a higher degree of internal plant damage. These results stress the importance of differential economic thresholds for stem borer control in plantings of different yield potential.