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Article

In Field Detection of Downy Mildew Symptoms with Proximal Colour Imaging

1
ITAP, Univ. Montpellier, INRAE, Institut Agro—SupAgro, F-34196 Montpellier, France
2
Univ. Bordeaux, IMS UMR 5218, F-33405 Talence, France
3
Centre National de la Recherche Scientifique, IMS UMR 5218, F-33405 Talence, France
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(16), 4380; https://doi.org/10.3390/s20164380
Received: 9 July 2020 / Revised: 28 July 2020 / Accepted: 2 August 2020 / Published: 5 August 2020
This paper proposes to study the potentialities of on-board colour imaging for the in-field detection of a textbook case disease: the grapevine downy mildew. It introduces an algorithmic strategy for the detection of various forms of foliar symptoms on proximal high-resolution images. The proposed strategy is based on structure–colour representations and probabilistic models of grapevine tissues. It operates in three steps: (i) Formulating descriptors to extract the characteristic and discriminating properties of each class. They combine the Local Structure Tensors (LST) with colorimetric statistics calculated in pixel’s neighbourhood. (ii) Modelling the statistical distributions of these descriptors in each class. To account for the specific nature of LSTs, the descriptors are mapped in the Log-Euclidean space. In this space, the classes of interest can be modelled with mixtures of multivariate Gaussian distributions. (iii) Assigning each pixel to one of the classes according to its suitability to their models. The decision method is based on a “seed growth segmentation” process. This step exploits statistical criteria derived from the probabilistic model. The resulting processing chain reliably detects downy mildew symptoms and estimates the area of the affected tissues. A leave-one-out cross-validation is conducted on a dataset constituted of a hundred independent images of grapevines affected only by downy mildew and/or abiotic stresses. The proposed method achieves an extensive and accurate recovery of foliar symptoms, with on average, a 83% pixel-wise precision and a 76% pixel-wise recall. View Full-Text
Keywords: proximal sensing; downy mildew; parametric classification; structure tensor; seed growth segmentation proximal sensing; downy mildew; parametric classification; structure tensor; seed growth segmentation
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MDPI and ACS Style

Abdelghafour, F.; Keresztes, B.; Germain, C.; Da Costa, J.-P. In Field Detection of Downy Mildew Symptoms with Proximal Colour Imaging. Sensors 2020, 20, 4380. https://doi.org/10.3390/s20164380

AMA Style

Abdelghafour F, Keresztes B, Germain C, Da Costa J-P. In Field Detection of Downy Mildew Symptoms with Proximal Colour Imaging. Sensors. 2020; 20(16):4380. https://doi.org/10.3390/s20164380

Chicago/Turabian Style

Abdelghafour, Florent, Barna Keresztes, Christian Germain, and Jean-Pierre Da Costa. 2020. "In Field Detection of Downy Mildew Symptoms with Proximal Colour Imaging" Sensors 20, no. 16: 4380. https://doi.org/10.3390/s20164380

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