Population dynamics of larger grain borer, a biosecurity threat to stored products in the USA

Larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), is an APHIS Species-of-Concern in the USA. This species is projected to expand its range under climate change into the southern USA. However, there have been relatively few attempts to model its baseline population dynamics if it does become established, which could then inform risk assessments for introduction. Here, we used thermal reaction norms to model population growth rates and predict region and seasonal specific population dynamics of P. truncatus using the package tidymodels and adjacent packages in R Software. In addition, we model how damage could progress after introduction based on estimates of damage potential per insect. We found that populations could be robust if introduced to the USA with excessive grain damage occurring. Combined with their good dispersal ability, infestations could spread quickly and likely grow exponentially higher in areas with large amounts of grain storage. Overall, our findings help inform biosecurity risk assessment for this species, and enhance our baseline understanding of its ecological niche.