A Comparison of Regression Tree Approaches to Modelling the Efficacy of Water Hyacinth Biocontrol Using Multitemporal Spectral Datasets

Abstract

Water hyacinth (Eichhornia crassipes) is an exotic plant species that is effectively controlled by Neochetina spp. weevils. This study is aimed at determining if spectroscopic data may be utilized to predict insect-induced stress on water hyacinth plants. Single target regression trees (STRTs), multitarget regression trees (MTRTs), and random forest multitarget regression trees (RF-MTRTs) have been used to predict feeding scar damage (FSD) and relative leaf chlorophyll content (RLCC) from hyperspectral canopy reflectance data. Results from this study show that the correlation coefficient of STRTs (training accuracy: 76%-97%; validation accuracy: 47%-86%) performs better than MTRTs (training accuracy: 74%-90%; validation accuracy: 45%-77%) for all infestation levels but are difficult to interpret simultaneously. In contrast, MTRTs (size: 23-35 nodes) are much smaller and more interpretable than STRTs (size: 11-47 nodes) because they predict FSD and RLCC simultaneously. Importantly, RF-MTRTs (training accuracy: 95%-98%; validation accuracy: 55%-88%) yield better predictive performance than STRTs and MTRTs for all infestation levels. It is concluded that MTRTs can be utilized for model interpretation as they are more interpretable; however, RF-MTRTs offer an improved predictive performance.