Induced em-spectral response for an early detection of vegetation (crop) biotic stress

Abstract

All vegetation is vulnerable to stress due to biotic or abiotic factors. Remote sensing technology is a useful tool in managing abiotic stress. However, it is limited to damage assessment for biotic stress. The objectives of this study are to determine the pre-symptom stage of ralstonia solanacearum infection in cucumber and to study the effects of nutrient content, water level and light exposure on the electromagnetic spectral response of cucumber leaves in the pre-symptom stage. In this study, hydroponic sets of inoculated and non-inoculated cucumber plants were grown in a controlled environment. A set of each inoculated and non-inoculated cucumber were subject to nutrient stress, water stress and light stress. Spectroradiometer measurements, photographs and notes were collected daily. Mean percent difference between inoculated and non-inoculated cucumber in normal condition of less than 15% indicates that data was collected during the pre-symptom stage of ralstonia infection. From the five vegetation indices used, the NRI, TVI and MCARI were successful in detecting a change in spectral reflectance in infected cucumber leaves that has been induced by light stress during the pre-symptom stage. This study has proven the hypothesis that a measurable change in spectral response can be induced for the early detection of vegetation biotic stress.