Levels of infestation on three different portions of the maize cob by the weevil Sitophilus zeamais (motschulsky)

Abstract

The maize weevil, Sitophilus zeamais is a major storage pest of maize that causes significant quantitative and qualitative losses to the farmer. The extent of damage caused by S. zeamais to stored maize depends on the initial level of infestation on the field before harvest. The levels of infestations on three different portions of maize cob were studied. Maize was planted during the minor planting season (September-December) of 2008. Maize seeds were sown on 9 plots each measuring 7.0 m x 1.5 m. Matured maize cobs were harvested 110 days after emergence. Ten cobs were randomly selected from each of the plots, dehusked and cut into three portions: top, middle and bottom and stored separately in sealed plastic containers for 5 weeks. Weevils were counted weekly during the storage period. Percent damaged seeds and numbers of holes on dam- aged grains were counted for each portion. Percent weight loss due to S. zeamais infestation was calculated for the different maize portions. Weevil infestations were recorded on all the portions 1 week after storage. Large numbers of S. zeamais were recorded on all the portions at the end of the storage period. The middle portion recorded significantly more S. zeamais than the top and bottom portions. Percent damaged seeds; percent weight loss and mean number of holes on damaged seeds did not differ significantly.