Results and Disscussions
1.1. Detection of Affected Plantations from Remotely Sensed Images
From the above results and discussions it is clear that one can easily identify the affected and non-affected tea patches from remotely sensed images. The disease started in the year 1999 but was not severe at the initial stage. During the year 2000 and 2001, there was heavy monsoon showers accompanied by high temperature and humidity. These conditions have favoured the spread of the disease. Between 2003 and 2005 the spread was quite severe. When the LANDSAT ETM+ (December, 2001), LISS III (February, 2004) and ASTER (June, 2004) images were compared, it was observed that there was a continuous shift in the disease from one place to another. The shift was minutely observed in all the images. It was further verified on the field. All the affected tea patches from 1999 to 2005 were identified from the garden records and from the field visit. The field records have shown that there was a rapid shift in the spread of the disease in the gardens. All the spots were visited and marked in the images and compared. From this it was quite clear that whatever has been visually interpreted from the image was correct and the shift in the disease could be well established. Figure 64, 65 and 66 showed the FCC showing the healthy and affected tea patches.