Abstract
Laboratory interspecific competition and grain-hosts selection experiments involving maize weevil (MW), Sitophilus zeamais (Motsch.) and larger grain borer (LGB), Prostephanus truncatus (Horn) were performed under ambient temperature and relative humidity (25°C - 35°C and 70% - 80% relative humidity) in their major host cereal, maize grains. The species reproductive rate and grain-hosts preference were evaluated by a number of emerged adults. In combined infestation, both species competed intensively by simultaneously increasing their individuals’ emergence, 9-fold or greater than when reared alone. Even though both species simultaneously increased their progeny, S. zeamais was the dominant competitor and had a significant suppressant effect on P. truncatus. The selection result of grain-hosts showed that P. truncatus placed in the environment containing both uninfested maize grains and grains previously infested by S. zeamais, the insect prefers uninfested grains. Indeed, P. truncatus individuals’ emergences were significantly more important to uninfested grains than to infested grains. The weevil-infested grains seemed to have deterrent and detrimental effects on P. truncatus. Conversely, S. zeamais selection of grain-hosts was significantly (P = 0.0001) more attracted by P. truncatus infested grains than to uninfested grains. Sitophilus zeamais individuals’ emergences were significantly (P = 0.0008) more important to infested grains than to uninfested grains. The S. zeamais preference on grains previously infested would be stimulated by P. truncatus larval vibrations in grain.
Highlights
In Africa, postharvest losses due to the pests, far outweigh the acceptable economic losses and contribute to high food prices by removing part of supply from the market
The selection result of grain-hosts showed that P. truncatus placed in the environment containing both uninfested maize grains and grains previously infested by S. zeamais, the insect prefers uninfested grains
The results of this work confirm that there is a real interspecific competition between Sitophilus zeamais and Prostephanus truncatus, this is likely to lead a significant increase in stored maize losses
Summary
In Africa, postharvest losses due to the pests, far outweigh the acceptable economic losses and contribute to high food prices by removing part of supply from the market. Insects are the principal pests [1] [2] and the most important insects are the maize weevil (MW), Sitophilus zeamais (Motsch.) (Coleoptera, Dryophtoridae) [3] [4] and the larger grain borer (LGB), Prostephanus truncatus (Horn) (Coleoptera, Bostrichidae) [2] [5] These two beetles often cause losses in excess of 20% of harvests after six to eight months of storage [6] [7] [8] and constitute a threat of food resource’s availability. Prostephanus truncatus is intercepted in Senegal in 2007 [14], and represents since a threat to maize conservation in the country These two insect species reduce maize germination, increase the grains moisture content [15] [16] and favor the storage contamination by fungi and bacteria [16] [17]. The coexistence of different insect species in grains storage can be due to their roles in ecological succession or their differences in the way that each insect infests the stored product, which of-
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