Identifying Plant Disease

NIR spectroscopy can be an effective tool for identifying plant diseases that affect agricultural production. An NIR field spectroradiometer can measure key indications of biotic stress caused by disease. Examples of diseases that can be identified with an NIR spectroradiometer include aflatoxins in corn, late blight disease, yellow leaf curl virus in tomatoes, leaf spot or powdery mildew in sugar beets, yellow rust in wheat, Fusarium infection in barley, and rice blast, to name a few. Infected leaves have a different spectral image than healthy leaves. The symptoms and stress caused by the pathogens change pigmentation, alter surface temperature, and reduce chlorophyll content.

By measuring reflectance with a full range spectroradiometer like the SPECTRAL EVOLUTION SR-6500, RS-8800, NaturaSpec™, PSR+, or RS-3500 with our unique leaf clip, the effect of pathogens on plants can be evaluated. In general, maximum differences in reflectance have been found in the range of 380–750 nm between plants subjected to biotic stress and healthy plants, along with high reflectance in the SWIR 1135-2400 nm range.

Using chemometrics software allows a researcher to create models for identifying different plant diseases. Our DARWin SP Data Acquisition software saves your spectra as ASCII files for use with analysis software such as chemometrics programs like Unscrambler from Camo Analytics. Unscrambler allows you to build, optimize and test your model. The coefficients from your model are used in the prediction engine built into our DARWin software to identify plant diseases in new samples.

Our field spectroradiometers allow for fast, non-destructive measurements in situ during all phases of crop growth. By monitoring and measuring the change in the spectral image of leaves, early detection of many diseases is possible. The progression of diseases, which is usually accompanied by an increase in severity and development of further symptoms like leaf area loss or lesions, can be arrested early treatment to reduce crop loss.

Scans of healthy leaf in green versus stressed leaf in blue in a multiple plot DARWIN SP display.