Population growth of native and invasive strains of the larger grain borer, Prostephanus truncatus on three maize hybrids

Authors: QUELLHORST, HANNAH - Kansas State University; SAKKA, MARIA - University Of Thessaly; ATHANASSIOU, CHRISTOS - University Of Thessaly; Morrison, William - Rob; ZHU, KUN YAN - Kansas State University

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2024
Publication Date: 5/26/2024
Citation: Quellhorst, H.E., Sakka, M., Athanassiou, C.G., Morrison Iii, W.R., Zhu, K. 2024. Population growth of native and invasive strains of the larger grain borer, Prostephanus truncatus on three maize hybrids. Crop Protection. 183: 106752. https://doi.org/10.1016/j.cropro.2024.106752.
DOI: https://doi.org/10.1016/j.cropro.2024.106752

Interpretive Summary: The larger grain borer is an invasive species in many countries in Africa, and an APHIS species-of-concern. It continues to threaten maize worldwide and makes its home in Mexico, Central and Northern South America, with the potential to expand into more temperate regions due to climate change. Insecticides have been used to manage this pest in many areas, but consumer demand for food products with reduced chemical residues is increasing and these insecticides are not always effective at preventing infestations as the immature larvae spend most of their life cycle feeding inside the grain and are largely protected from insecticides. To help manage this pest, maize hybrids with resistance to larger grain borer were created from African cultivars in the 1990s and have proven successful for minimizing feeding damage. However, the susceptibility of existing locally adapted maize cultivars grown in areas where larger grain borer has yet to fully establish, including parts of Europe (Italy and Greece), have not been investigated for resistance to larger grain borer. This information is important for understanding the risk that this species poses to different parts of the world. To fill this knowledge gap, we compared population growth of two different strains of larger grain borer (one from the native range in Mexico and one from the invaded range in Ghana) reared on three different maize cultivars commonly grown in Greece. Interestingly, we found the native strain produced 15% fewer progeny on all three cultivars; however, both strains caused equal and extensive damage on all three hybrids. This finding shows that maize varieties commonly grown in Greece are susceptible to larger grain borer, but that genetic differences between strains may impact fitness levels and progeny production. Overall, this study provides a platform exploring maize host-plant resistance as a possible new tool for protecting maize production after harvest in Europe and other parts of the world.

Technical Abstract: The larger grain borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae), continues to threaten maize worldwide, with an endemic range in Mexico, Central and Northern South America, and an exotic range in Sub-Saharan Africa, with the potential to expand into more temperate regions due to climate change. Insecticides have been mostly used against this pest, however there was a targeted effort beginning in the 1990s to create maize hybrids for the management of P. truncatus. Through the efforts of that project, several resistant maize hybrids were developed. However, where P. truncatus has yet to fully establish, including parts of Europe such as Italy and Greece, existing maize hybrids have not been investigated against P. truncatus. In this study, we sought to (1) compare two different strains of P. truncatus, one from the native range in Mexico and one from the invaded range in Ghana and (2) investigate the progeny production, number of damaged kernels, and frass production of both strains on three susceptible maize hybrids developed for use in Greece and wider Europe. We found that progeny production between the two insect strains was different across the three maize hybrids, with the native strain of P. truncatus performing more poorly compared to strain from the invaded range. There were no real differences in damage or frass production between the two strains and across the three maize hybrids. Overall, this is the start of work in Europe exploring maize resistance as a possible new tool for protecting maize production.