In situ spectral characterization of sugar cane infected by nematodes and Migdolus fryanus

Despite all technological support used in sugarcane cultivation in Brazil, this planting is still subject to the action of root pathogens. Due to its ability to selectively record the spectral flux of electromagnetic radiation reflected by vegetation, remote sensing is a powerful tool in detecting plants infected by pests and parasites. The objective of this work was to characterize the spectral response of healthy sugarcane and its plants infected by nematodes and Migdolus fryanus beetle larva. In situ radiometric measurements were performed and specific spectral analysis techniques, such as Red Edge Position Determination (REPD) and different vegetation indices were evaluated to discriminate these occurrences. The reflectance curves generated showed differences in magnitude mainly at red and near-infrared wavelengths and, as well as REPD, chlorophyll b index, NDVI, MCARI and TCARI, were able to discriminate only healthy and infected plants. The spectral ratios sensitive to chlorophyll a and carotenoids pigments, however, discriminated the three occurrences, including nematode-infected plants and Migdolus fryanus. The best discrimination was obtained by the index of carotenoids, a pigment whose content is related to plant stress.

Keywords:
hyperspectral remote sensing; sugarcane pests; root pathogens; spectral analysis; vegetation index