Trace Identification and Visualization of Multiple Benzimidazole Pesticide Residues on Toona sinensis Leaves Using Terahertz Imaging Combined with Deep Learning

Abstract

Molecular spectroscopy has been widely used to identify pesticides. The main limitation of this approach is the difficulty of identifying pesticides with similar molecular structures. When these pesticide residues are in trace and mixed states in plants, it poses great challenges for practical identification. This study proposed a state-of-the-art method for the rapid identification of trace (10 mg·L−1) and multiple similar benzimidazole pesticide residues on the surface of Toona sinensis leaves, mainly including benzoyl (BNL), carbendazim (BCM), thiabendazole (TBZ), and their mixtures. The new method combines high-throughput terahertz (THz) imaging technology with a deep learning framework. To further improve the model reliability beyond the THz fingerprint peaks (BNL: 0.70, 1.07, 2.20 THz; BCM: 1.16, 1.35, 2.32 THz; TBZ: 0.92, 1.24, 1.66, 1.95, 2.58 THz), we extracted the absorption spectra in frequencies of 0.2–2.2 THz from images as the input to the deep convolution neural network (DCNN). Compared with fuzzy Sammon clustering and four back-propagation neural network (BPNN) models (TrainCGB, TrainCGF, TrainCGP, and TrainRP), DCNN achieved the highest prediction accuracies of 100%, 94.51%, 96.26%, 94.64%, 98.81%, 94.90%, 96.17%, and 96.99% for the control check group, BNL, BCM, TBZ, BNL + BCM, BNL + TBZ, BCM + TBZ, and BNL + BCM + TBZ, respectively. Taking advantage of THz imaging and DCNN, the image visualization of pesticide distribution and residue types on leaves was realized simultaneously. The results demonstrated that THz imaging and deep learning can be potentially adopted for rapid-sensing detection of trace multi-residues on leaf surfaces, which is of great significance for agriculture and food safety.

Application of machine learning to the monitoring and prediction of food safety: A review

“…Nie et al. (2021) use deep learning combining with a terahertz imaging method to identify and visualize multiple benzimidazole pesticide residues on toona sinensis leaves. Chakraborty et al.…”

“…Studies mainly focus on the identification and detection of toxins (Chakraborty et al., 2021; Liang, Huang et al., 2020), pesticide residues (Gui et al., 2019; Mohite et al., 2017; Nie et al., 2021), and food additives (Šojić et al., 2019), as well as the estimation or prediction of the presence of heavy metals (Petrea et al., 2020; Yu et al., 2018). Nie et al.…”

Applications of THz Spectral Imaging in the Detection of Agricultural Products

“…Compared with conventional techniques used for pesticide detection, THz spectroscopy imaging enables qualitative, quantitative, and graphical analysis. In recent years, there has been a significant interest in employing THz imaging for detection of pesticides [1,84,85]. Lee et al [86] proposed a novel high-sensitivity, selective method for detecting pesticide residues, where nano-scale metamaterials were used based on a THz-TDS system to detect methomyl.…”

Sequencing and analysis of the complete mitochondrial genomes of Toona sinensis and Toona ciliata reveal evolutionary features of Toona

“…Even though Toona plants have a long history of cultivation in China, most studies have been limited to chemical pathology, physiology, biochemistry, introduction, and breeding, with little research done on its origin, taxonomy, cytogenetics, and so on. There are still some issues with Toona classification, such as interspecific hybridization, that need to be addressed [33,34]. Furthermore, Toona plants have a geographically dispersed distribution in China, resulting in a scarcity of natural forests and susceptibility to natural and anthropogenic breakage, T.ciliata has now been classified as an endangered species, listed as a Class II key protected wild plant in China, and included in the Reference List of Major Cultivated Precious Tree Species in China and [35][36][37][38].…”