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ViewAttendees 6

Member Symposium

Farm to Fork: Linking Biology of Postharvest Insects to their Management

9: Patterns and mechanisms for niche partitioning between the larger grain borer (Prostephanus truncatus) and the maize weevil (Sitophilus zeamais) and its implications for management of stored maize

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Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), the larger grain borer, is endemic to Central America, but invaded Africa with disastrous consequences for maize production. Its main competitor is Sitophilus zeamais Motschulsky (Coleoptera: Cucurlionidae), the maize weevil, which has a more cosmopolitan distribution. With a warming climate, the range of the primarily tropical P. truncatus may shift polewards and invade maize stores already containing S. zeamais. The aims of our study were to evaluate the outcome of interspecific competition between P. truncatus and S. zeamais at different temperatures on a fixed quantity of grain, and determine the effects on progeny production, grain damage, and mold growth in mixed or single-species colonies. We found that coexistence may be possible under several temperatures, but mixed colonies experienced a direct competitive cost compared to colonies containing only conspecifics. The majority of the grain damage was the result of P. truncatus activity, but not S. zeamais activity. Finally, mold growth was greater where both species were present, and mycotoxin-producing species of mold were identified. These results suggest that as there are an increasing number of areas where both species co-occur, food facilities may experience increased insect and mold damage, which may require novel tactics to adapt.