The incidence of<i>Chilo partellus</i>(Swinh.) (pyralidae) and the contribution of natural enemies to its mortality under intercropping system in Kenya

Abstract

Abstract In the present study the incidence of Chilo partellus and its mortality due to natural enemies on sorghum intercropped with cowpea and maize were investigated in the 1984–6 cropping seasons. The lowest larval density was recorded in sorghum/ cowpea intercrop (mean 0. 18 larvae/plant); and the highest density in sorghum/maize (mean 1. 8 larvae/plant), although significant differences in larval density were observed only in three out of five seasons. Life table analysis showed first‐generation mortality of C. partellus to be highest in the age interval from egg to early‐instar larva (95–98% real mortality) and attributable mainly to predation; first‐generation mortality due to parasitoids and pathogens was negligible. Significantly higher (P < 0. 05) apparent pupal mortality due to Dentichasmias busseolae (Heinrich) (Ichneumonidae), in the second generation occurred in sorghum/cowpea (42.8%) than in sorghum/maize (12.5%). It was concluded that predators play a significant role and that intercropping sorghum with cowpea or maize does not interfere with their activity. Intercropping sorghum with cowpea gave nearly 40% higher yield index than sorghum monocrop. The implications of these findings on management