Abstract

Sitophilus zeamais Motsch. is  one  of  the  most  important  pests  of  sorghum  in  storage  causing  severe economic damage to the grain. Twenty-one sorghum varieties obtained from Haramaya University Sorghum Improvement Research Program were investigated for their relative resistance to S. zeamais attack. The Dobie index of susceptibility was used to group the varieties into different reaction categories. Among the twenty one sorghum varieties evaluated, only one variety, ‘WB-77’, was regarded as resistant to the weevil. All the remaining varieties were categorized as moderately resistant. Weevils reared on the resistant variety produced a few number of F₁ progeny (20.00), had a high median developmental time (42.00 days) and a low percentage of seed damage (2.67) and seed weight loss (0.30). Percentage seed damage and weight loss are significantly and positively correlated with the mean number of F₁ progeny emergence and are inversely associated with median developmental time. Consequently, those varieties with high number of F₁ progeny scored high percentage of seed damage and weight loss. These results indicated that high lysine content was found to be the predominant factor in sorghum resistance to S. zeamais.

Key words: Sorghum varieties, resistance, insect infestation, Sitophilus zeamais, susceptibility index.