Assessment of Late Blight Induced Diseased Potato Crops: A Case Study for West Bengal District Using Temporal AWiFS and
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RESEARCH ARTICLE
Assessment of Late Blight Induced Diseased Potato Crops: A Case Study for West Bengal District Using Temporal AWiFS and MODIS Data Sujay Dutta & Suresh K. Singh & Sushma Panigrahy
Received: 31 January 2013 / Accepted: 3 September 2013 / Published online: 27 December 2013 # Indian Society of Remote Sensing 2013
Abstract Remote sensing technology becomes an effective and inexpensive technique for detecting disease in vegetation. In this study, an attempt has been done to discriminate healthy and late blight affected crop using remote sensing based indices such as NDVI and LSWI. NDVI and LSWI spectral profiles between healthy and late blight affected crop shows large difference. Mean difference in reflectance between two acquired dates Jan. 10 and 29, 2009 crop clusters varied from 31.28 % in red band, 7.7 % in NIR band and 6.23 % in SWIR bands in healthy crops while in late blight affected crops it is −15.5 % in red, 44.4 % in NIR and −14.61 % in SWIR bands. Negative percentage differences in reflectance indicate reflectance increases from Jan. 10, 2009 to Jan. 29, 2009, while positive difference indicate decrease in reflectance between the two dates. Since potato is an irrigated crop, these differences in reflectance are attributed to prevalent disease at that time. It is found that severely affected areas are Bardhman, Arambag, Bishnupur, Ghatal and Hugli taluka with crop damage areas are 4036.66, 1138.68, 2025.23, 469.15, and 380.08 ha, respectively. Keywords Remote sensing . Winter potato . Late blight disease . NDVI . LSWI
Introduction Potato is a cash crop and cultivated extensively in northern states of India. Remote sensing has the potential to be used as an effective and inexpensive technique to identify diseased S. Dutta (*) : S. K. Singh : S. Panigrahy Crop Inventory & Agro-ecological Modeling Division/ABHG, EPSA, Space Applications Centre (ISRO), Ahmedabad 380015, India e-mail: [email protected]
plants in; mainly infected plants have different spectral response compared to healthy plants (Zhang et al. 2002). When plants get stressed with disease, absorption of incident light changes in the visible and Near Infra Red (NIR) range, this is probably due to the decreased chlorophyll content, changes in other pigments & internal structure. The change of absorption consequently influences the reflectance of stressed plants. Therefore, by comparing the spectral difference of stressed and healthy plants, we are able to identify the severely stressed green vegetation. Since the chlorophyll content tends to decrease under disease stress, absorption of incident solar radiation by green plants decrease in the visible region. Consequently, spectral reflectance is higher in the red region and decrease in the NIR range depending on the infection severity. Wisler and Duffus (2000) have studied late blight in tomato fields in California, caused by the fungal pathogen Phytophthora infestans, which spreads quickly during growing season. Humid air with high temperature are favourable for outbreak of
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