Competition of Prostephanus truncatus with Sitophilus oryzae on maize: The species that gets there first matters

Authors: BALIOTA, GEORGIA - University Of Thessaly; Scheff, Deanna; Morrison, William - Rob; ATHANASSIOU, CHRISTOS - University Of Thessaly

Submitted to: Bulletin of Entomological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2021
Publication Date: 5/6/2022
Citation: Baliota, G.V., Scheff, D.S., Morrison Iii, W.R., Athanassiou, C.G. 2022. Competition of Prostephanus truncatus with Sitophilus oryzae on maize: The species that gets there first matters. Bulletin of Entomological Research. https://doi.org/10.1017/S000748532100105X.
DOI: https://doi.org/10.1017/S000748532100105X

Interpretive Summary: Grain after it is harvested and stored can become infested by multiple insect species which can lead to competition for a shared resource. This competition can impact species diversity and levels of damage to the grain. Laboratory experiments were conducted to examine population growth of the larger grain borer and the rice weevil when they co-occur on corn. This research will shed light on the potential for establishment of the larger grain borer in non-native countries, such as the United States. Temperature played a key role in the competition of these two species; larger grain borer seemed to perform better at the higher temperature (30° C compared to 26° C), regardless of the presence of an additional species. When larger grain borer was the first species that was introduced in the vials, it outcompeted the rice weevil, but the reverse was not true. Rice weevil produced fewer progeny than the larger grain borer in all combinations, and only performed well in vials of corn that contained only rice weevil. Given the outcome of competition, we hypothesize that most of the measured grain damage was due to feeding by the larger grain borer. Based on these data, we surmise that the larger grain borer has a competitive advantage as an invasive species in new areas with stored maize, even in the presence of the rice weevil.

Technical Abstract: Laboratory tests were carried out in order to examine population growth of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and Sitophilus oryzae (L.) (Coleoptera: Curculionidae) on maize. These two species were placed either simultaneously or one species was allowed to colonize the grain 7 days earlier than the other, at two temperatures, 26 and 30 deg C for 65 days. Apart from progeny production, grain quality parameters, such as insect damaged kernels (IDK) and undamaged kernels (NDK), weight of frass and grain weight were measured. Our data confirms that temperature plays a key role in the competition of these two species; P. truncatus seems to perform better at the higher temperature (30oC), regardless of the presence of an additional species. Moreover, the results of the present study demonstrate that when P. truncatus was the first species that was introduced in the vials, it outcompetes S. oryzae, but the reverse was not true. Sitophilus oryzae produced fewer progeny than P. truncatus in all combinations, with the exception of vials that contained only S. oryzae. Given the outcome of competition, we hypothesize that most of the grain damage was due to feeding by P. truncatus. Based on these data, we surmise that P. truncatus has a competitive advantage as an invasive species in new areas with stored maize, even in the presence of S. oryzae.