Novel implementation of laser ablation tomography as an alternative technique to assess grain quality and internal insect development in stored products

Authors: Morrison, William - Rob; LANBA, ASHEESH - Laser For Innovative Solutions (L4IS); HALL, BENJAMIN - Laser For Innovative Solutions (L4IS); Bruce, Alexander

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2019
Publication Date: 3/1/2020
Citation: Morrison III, W.R., Lanba, A., Hall, B., Bruce, A.I. 2020. Novel implementation of laser ablation tomography as an alternative technique to assess grain quality and internal insect development in stored products. Journal of Stored Products Research. 86:101552. https://doi.org/10.1016/j.jspr.2019.101552.
DOI: https://doi.org/10.1016/j.jspr.2019.101552

Interpretive Summary: Internally-infesting insects cause major damage to grains such as wheat, rice and corn in the post-harvest agricultural supply chain. Because these insects develop inside the kernel, they are hard to detect, and their damage is hard to quantify, though it may be very significant. In the last century, there have been important advances in technologies to detect insects within kernels and to evaluate how they damage grain internally while they develop. These technologies have included electrical conductance mills, acoustical tools, near-infrared spectroscopy, and soft X-ray imaging. Each technique has their own advantages and limitations. In this current study, we describe a new way to evaluate and quantify the internal grain environment, including tracking insect development and measuring levels of internal grain loss. This technique is termed laser ablation tomography (LATscan) and we compare it to soft X-ray imaging using larvae, pupae and adults of maize weevil and lesser grain borer inside wheat kernels. Both of these species develop internally, are difficult to detect, and their damage is hard to quantify, though each are cosmopolitan and important stored product pests. Our results suggest that X-rays overestimated grain volume loss by about a quarter compared to LATscan. Moreover, LATscan produces a rich digital dataset on the level of microns that can be explored to ask biologically-relevant questions that include when development ceases after exposure to insecticides, when and how oviposition occurs on grain (which is usually missed by X-rays), and how insects interact with other types of pests such as mold and microbes. Ultimately, LATscan may be a useful additional tool to investigate how internal feeding pests of grain develop and damage grain by tunneling inside the kernels, while relating the level of damage to environmental conditions and grain characteristics such as moisture and protein content.

Technical Abstract: In the last century, there have been important advances in peering inside the internal grain environment. This has included electrical conductance mills, acoustical tools, near-infrared spectroscopy, and soft X-ray imaging. Each technique has their own advantages and limitations. In this current study, we describe a novel process for assessing grain quality and internal insect development in grain using laser ablation tomography (LATscan) and compare it to soft X-ray imaging for three life stages (larva, pupa, adult) of Sitophilus zeamais and Rhyzopertha dominica. Our results suggest that X-rays overestimated grain volume loss by about a quarter compared to LATscan. Moreover, LATscan produces a rich digital dataset on the level of microns that can be explored to ask biologically-relevant questions. We discuss the current limitations of LATscan in context with other techniques. Ultimately, the results highlight LATscan as a useful additional tool to further our understanding pest-commodity interactions in the postharvest supply chain.