Potential of spectroscopic data sets for sugarcane thrips (Fulmekiola serrata Kobus) damage detection

Abstract

Sugarcane thrips was detected in South African sugarcane in 2004. Since then it has become widespread in South Africa. The South African Sugarcane Research Institute (SASRI) conducts field surveys to monitor this pest, but this is time intensive and costly. As a first step towards evaluation of remote sensing for thrips monitoring, a preliminary experiment and analysis at leaf level were conducted using a handheld field spectroradiometer covering the 350 to 2500 nm range of the electromagnetic spectrum to detect sugarcane thrips damage. Reflectance spectra of sugarcane leaves with different levels of thrips damage, from two popular varieties (N19 and N12), were measured and statistically analysed using one-way analysis of variance, sensitivity analysis and canonical discriminant analysis. The results of the analyses showed that there were significant differences in spectral reflectance and derived variables used in the study at the different levels of damage. The red edge region of the visible portion gave the highest significant differences and levels of separability among the damage classes. It is hypothesized that this might be associated with chlorophyll and nitrogen deficiencies induced by thrips.

Acknowledgements

We thank SASRI extension specialist Mr Marius Adendorff for providing the leaf samples. We extend our thanks to SASRI's thrips survey team and technicians for their keen help in leaf samples storage. We also thank Mr Franko Sokolic for his assistance in the configuration of the field spectroradiometer. Thanks to the anonymous reviewers for their useful comments.