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

Abstract

The population growth of different strains of the larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), a key pest of stored maize, was evaluated at a range of temperatures. Three different strains of P. truncatus with different geographic origins (USA, Mexico and Tanzania) were left for 45 or 70 d to develop and reproduce under six temperatures (25, 30, 32, 35, 38 and 40 °C). 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 fast development and serious infestations was found to be 25–32 °C, which resulted in newly-emerged adults after 45 days. Differences were observed between the strains, both in terms of their growth rate and the damage they caused on the kernels over time. The present study aims to highlight how the strain is a factor of significance for P. truncatus based on the different thermal responses. These data can support more accurate prediction or elimination of future infestations, targeting immediate and early detection of the pest in areas where it is likely to establish.