Response of Cowpea Beetle to Food Quantity and Methods of Sterilization and Effects of Age and Storage Methods on Maize Weevil

• R.A. Adebayo

  Department of Crop, Soil and Pest Management, Federal University of Technology, P.M.B. 704 Akure, Nigeria

  Author

Cowpea beetle (Callosobruchus maculatus (F.) and maize weevil (Sitophilus zeamais Mots.) are two serious insect pests of stored grains in the tropics. Experiments were conducted at the Department of Crop, Soil and Pest Management, the Federal University of Technology, Akure, Nigeria to determine the influence of food quantities and methods of sterilization on the development of C. maculatus and to evaluate the effects of age and storage method on the performance of S. zeamais under laboratory conditions. Results revealed significant differences (p<0.05) in the mean number of seeds with eggs, seeds without eggs, seed weight loss and number of seeds with holes. However, no significant differences existed in mean number of eggs laid and number of emerged adults though highest number of eggs was recorded for C. maculatus provided with 20g of cowpea seeds. Investigations also revealed that methods of sterilization did not have significant effect on number of eggs laid, number of emerged adults and number of seeds with eggs. However, methods of sterilization had significant effect on number of seeds with eggs. Highest number of eggs was laid on and the lowest number of adults emerged from seeds heat sterilized at 60C and acclimatized for 3hrs. It was however observed that the weight of infested cowpea seed reduced substantially with damage by the cowpea beetle. Results from the study also revealed that despite non-significant effect (p>0.05) of insect age on the number of emerged adults at first month of maize storage, insect age had significant effect on seed weight loss, with the highest weight loss value was obtained from grains infested with 3 days old insects. Insect age did not have significant effect (p>0.05) on the number of adults that emerged and seed weight loss when the seeds were stored for 2 months. Generally, 3 days old insects performed better than insects of other ages. Storage materials did not have significant effect on the number of emerged adults and weight loss at both 1 and 2 months of maize storage period. However, lowest number of adults emerged from grains stored in polythene bag while the lowest weight was lost on grains stored in glass jar at 1st month of storage. Based on the results from this study, it was evident that food quantity and method of sterilization could be among the factors that determine performance of C. maculatus in the laboratory while age of infesting adults and storage material could influence the depredative capacity of the maize weevil on maize during storage.

1. R.A. Adebayo, Department of Crop, Soil and Pest Management, Federal University of Technology, P.M.B. 704 Akure, Nigeria

   Department of Crop, Soil and Pest Management, Federal University of Technology, P.M.B. 704 Akure, Nigeria

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