Short-term spatial niche partitioning between the larger grain borer and the maize weevil in grain columns with implications for management of stored maize

Authors: QUELLHORST, HANNAH - Kansas State University; KIM, TANIA - Kansas State University; ZHU, KUN YAN - Kansas State University; Morrison, William - Rob

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2023
Publication Date: 2/1/2024
Citation: Quellhorst, H.E., Kim, T.N., Zhu, K., Morrison III, W.R. 2024. Short-term spatial niche partitioning between the larger grain borer and the maize weevil in grain columns with implications for management of stored maize. Environmental Entomology. 53(1):127-142. https://doi.org/10.1093/ee/nvad111.
DOI: https://doi.org/10.1093/ee/nvad111

Interpretive Summary: The invasive larger grain borer is expected to move northward into the US under climate change, creating difficulties for postharvest corn protection, and has already been historically caught along the southern tier of states. Maize weevil is already a problem for postharvest maize protection in many parts of the world, including the US. It is important to understand how these two species will interact when they are in the same area, and while competition between the two has been studied extensively, there is little information on whether they occupy the same part of a grain column in bulk storage situations. In evaluating short-term behavior in yard-high single layers of corn kernels (e.g., monolayer), we found that both species generally aggregated together and were found in the same location in the monolayer of grain. After 24 hours, most of the insects for both species were near the top of the monolayer, but by 7 days, most individuals were in the bottom of the monolayers. When alone, larger grain borer created a clear path of destruction to the bottom of the monolayer, but when maize weevil was also present, damage was lessened and shifted upwards in the grain column. These data may improve targeting of pest control tactics by identifying the position of these insects in the grain mass and how larger grain borer, which poses a biosecurity threat to the US, interacts with a species that is already present.

Technical Abstract: The invasive Prostephanus truncatus, the larger grain borer, and Sitophilus zeamais, the maize weevil co-occur in many regions of the world. While competition between these two species has been studied extensively, there is little information on spatial partitioning in bulk storage of grain. To evaluate potential overlap in realized niche, we evaluated the short-term niche partitioning behavior of P. truncatus and S. zeamais in monolayers of maize alone or together for 1 d compared to 7 d. We evaluated competition under three different densities, namely 10–20, 75–150, and 150–300 insects/kg for P. truncatus and S. zeamais. The monolayers were equally divided into 24 zones to track location the abundance of insects and damage on maize. We found that both species generally aggregated together and were correlated to the same location as heterospecifics. After 1 d, most of the insects for both species were near the top of the monolayer, but by 7 d, most individuals were in the bottom of the monolayers. In monolayers, when alone, P. truncatus created a clear path of destruction to the bottom of the monolayer, but when S. zeamais was present, damage was lessened and shifted upwards in the grain column. In an olfactometer assay, P. truncatus preferred maize odors, while S. zeamais exhibited no preference among maize, conspecifics, and heterospecifics. In evaluating relative emissions, each of these treatments emitted unique odors but with significant overlap. These data may improve targeting of pest control tactics by identifying the position of these insects in the grain mass.