Effect of Sorghum-Cowpea Intercropping on Sorghum Stem Borers and Their Parasitoids in Northern Ethiopia

Abstract

The influence of sorghum-cowpea intercropping on the occurrence of stem borers in sorghum and their parasitoids was investigated at Abergele in Tigray Region, northern Ethiopia. Four intercropping and two monocropping systems arranged in randomized complete block design in four replications were used. Abundance of egg masses, larval and pupal stages of stem borers were significantly greater in the monocropped sorghum than sorghum-cowpea intercropped plots. Among the identified stem borers, Busseola fusca accounted for 55%, Chilo partellus 31%, Sesamia calamistis 12%, and Rynchaenus niger 2%. R. niger was a new insect pest recorded on sorghum for northern Ethiopia. The population of C. partellus was higher early in the growing season, while B. fusca dominated lately. Whereas, R. niger occurred at the end of the growing season. Cotesia sesamiae, C. flavipes, and Sturmiopsis parasitica parasitized lepidopterous stem borers larvae at low levels, ranging from 0.4% in the monocropped to 0.7% in the intercropped plots. The levels of larval parasitism of stem borers were not different between the intercropped and monocropped plots. The sorghum-cowpea intercropping systems significantly reduced the density of stem borers. Therefore, the system can be used as an important component of stem borer management.