At harvest taller plants of both sorghum and maize produced a greater grain yield, but under intercropping conditions maize always out-yielded sorghum when planted at the same time, whether the sorghum was planted in the same hill as maize, or in alternate hills, or in alternate rows. There were generally more stem-borers in sorghum than in maize, with Chilo partellus predominating. Intercropping increased the level of stem-borers in maize, while infestation was very low in pure stands of maize, and the level of borer infestation in sorghum remained the same. Borers had a considerable effect on yield of maize at Mbita Point, on the shores of Lake Victoria: an infestation level of 38–52% of internodes bored resulted in significant yield loss. Implications of these results for predicting yield reduction due to stem-borers is discussed.
