Strain effect of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) in population growth studies on different temperatures

Authors: BALIOTA, GEORGIA - University Of Thessaly; PAPADIMITRIOU, ELENI - University Of Thessaly; Scully, Erin; ATHANASSIOU, CHRISTOS - University Of Thessaly

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2024
Publication Date: 1/19/2024
Citation: Baliota, G.M., Papadimitriou, E., Scully, E.D., Athanassiou, C.G. 2024. Strain effect of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) in population growth studies on different temperatures. Journal of Economic Entomology. 178. Article 106594. https://doi.org/10.1016/j.cropro.2024.106594.
DOI: https://doi.org/10.1016/j.cropro.2024.106594

Interpretive Summary: Larger grain borer is a significant pest of stored maize throughout much of the world, although it has not yet become permanently established in the United States. As internal feeders whose immature stage feeds and develops inside maize kernels, control of this pest with insecticides is difficult, but heat treatments are often used to suppress pest populations. Although information regarding optimal environmental conditions for population growth, such as temperature and humidity, are known for this species, it is unknown if populations collected from different geographic regions are adapted to different temperatures. In this study, populations of larger grain borer collected from the USA, Mexico and Tanzania were reared at six different temperatures 25, 30, 32, 35, 38 and 40C and population growth and insect feeding damage were measured. Optimal rearing temperatures for all three populations was between 25 to 32C and developmental time from egg to adult was under 45 days for all three populations. However, the population levels of the US population expanded more slowly at higher temperatures (>35C) compared to the other two strains. This illustrates for the first time that different populations of this stored product pest can be adapted to different temperatures, which can greatly influence population growth and their susceptibility to heat treatments.

Technical Abstract: The strain effect on the population growth of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), a key pest of stored maize, was evaluated towards a wide range of temperatures. For this purpose, three different strains of the species with different geographic origin (USA, Mexico and Tanzania) were left for 45 or 70 d to develop and reproduce under six temperature levels of 25, 30, 32, 35, 38 and 40C. Progeny production and maize-infestation indicators (frass, damaged maize kernels) were examined to estimate possible differences between the strains in terms of development performance and optimal thermal requirements. Population growth of the species appeared to be affected by the combination of temperature and/or developmental period. The optimum temperature range for quick development and serious infestations found to be within 25 to 32C, with newly-emerged adults after 45 days. Additionally, differences were observed between the strains, both in terms of their growth rate and the spoilage they caused on the kernels over time. The present study aims to highlight the strain as a factor of significance for P. truncatus based on the different thermal responses. These data are necessary for the accurate prediction or elimination of future infestations, aiming at the immediate and early detection of the pest in areas where is likely to establish.