Feeding by Adults of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) on Shelled Maize: Influence of Damaged Grain, Adult Crowding and Grain Density

In the laboratory, adults of Prostephanus truncatus (Horn) preferred artificially or naturally (insect) damaged maize kernels to sound kernels when adults were tested individually or in groups. Survival of P. truncatus was similar when I, 10, 40 or 80 adults were fed 100 g of shelled maize for 20 days; but more kernels were damaged at the highest adult density in comparison to the other densities of adults. Single P. truncatus adults on average damaged 9 maize kernels, but 10, 40, and 80 adults damaged approximately 15, 21 and 45 kernels, respectively, indicating that adults confined their feeding to only specific kernels. Survival of adults and number of kernels damaged were significantly affected when different quantities of shelled maize (25–500 g) were infested with 25 adults of P. truncatus. Adult survival at 25, 50, 100, and 200 g of maize/0.95–1 jar was similar (70.7–76.0%), but the number of kernels damaged increased significantly from approximately 15 at 25 g to 61 at 200 g. These results suggested that shelled maize grain compaction, which is influenced by the quantity of grain, may affect survival of and damage by adults of P. truncatus. Adults of P. truncatus successfully infested 25 g of shelled maize and damaged about 15 kernels, indicating that adults could temporarily survive on such small quantities of grain spilled in and around storages before infesting stored-maize.