Detection of Spodoptera litura F. using an electronic nose: A novel approach for monitoring vegetable crop pests

Abstract

The common cutworm, Spodoptera litura, is an economically important insect pest worldwide. However, outbreaks and control failures are frequently reported, with infestations often detected by farmers only after severe damage has occurred. This study aimed to apply an electronic nose (e-nose) based on eight metal oxide semiconductor (MOS) gas sensors to detect insect odors emitted from different stages of S. litura and volatile organic compounds (VOCs) released from their infested host plants. In laboratory tests, a prototype e-nose equipped with eight TGS sensors successfully detected various insect odors from different developmental stages and numbers of individuals (0.31–41.04 %). Older larvae and higher numbers of insects induced higher sensor responses. The e-nose also distinguished between two closely related species, S. litura and S. exigua. Additionally, plant VOCs released from pak choi (Brassica rapa) leaves with more than 5 % damage caused by S. litura larvae were more readily detected by the e-nose compared to leaves cut with scissors or undamaged plants. The e-nose also detected insect odors from S. litura larvae and plant VOCs from infested plants at distances of up to 40 cm. In greenhouse tests, the e-nose began detecting differences in insect odors and plant VOCs measurements between S. litura-infested and healthy plants when neonate larvae invaded plant leaves. This study demonstrates the potential of the e-nose equipped with eight TGS sensors as a detection tool for S. litura infestations in crop production.