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Introduction

1.5. Economic Impacts of Remote Sensing and GIS in Tea Sector:
The benefits from using RS and GIS technology depend on the level of success of its application for solving a concrete task. In general, these benefits can be divided into four categories such as scientific, technological, methodological, and economic efficiency (Badarch, 1990). The scientific efficiency of remotely sensed data also includes obtaining new facts for corroboration and quantitative clarification of previously known, qualitatively studied data. Technological efficiency means increasing of the work productivity (mainly the most expensive field job), making norms for fieldwork and speeding up the process of tea mapping, reducing the fieldwork volume, shortening the time necessary for surveys and reducing the number of personnel engaged in tea garden surveys. Methodological efficiency means increasing the accuracy and detail of spatial research of tea resources and also of observing widespread and dynamic processes and phenomena. Finally, economic efficiency of remote sensing data applications to natural resources can be expressed both directly (in the reduction of the cost of mapping) and indirectly (by an increase in the quality, reliability, detail, and information of the results). The economic benefits of using remote sensing are very difficult to estimate. The cost of remote sensing data is dependent on the cost for the entire system, consisting of data acquisition, processing and analysis components. This can be broken down into major cost items as follows: satellite development and operation, ground receiving stations and pre-processing facilities, and data processing, analysis and presentation to user community (Nanayakkara, 1990). Satellite remote sensing system produce the data provided by ground systems and airborne surveys in a much more intensive (detailed) and specific nature and is project oriented.

Based on the benefits and application of remote sensing and GIS, the tea sector has adopted this approach for studying the loss made by the gardens due to various reasons. Though the gardens are suffering from various losses the major cause of concern for the gardens is the heavy infestations caused by Red Spider attack and Helopeltis (Tea Mosquito Bug). So in this project initiatives have been taken to study the bush health using texture analysis and how the bush health is affecting the yield. Now the question arises as to what is red spider attack and Helopeltis attack.

A brief description of the two diseases is given below:

1.5.1. Symptoms of Helopeltis and it’s affect on the garden:

• Mosquito bugs are found in almost all tea growing areas of Assam.
• Both young and adult mosquito bugs damage tea plants by sucking the sap from tea buds.
• Nymphs caused severe damage than adults.
• The affected part of the plant develops a circular stain that is dark brown or black.
• Buds or shoots becomes curled, dried and black producing no yield.
• Badly damaged buds affect the next flush of shoots.
• Affected buds and shoots become infected with the disease of tea stem leprosy where the stems are covered with dark pimples or with swollen trunk disease.
• Most seriously affected plants developed dark green colour and are stunted.
• Mosquito bugs starts from a small area and then spreads to the entire garden.
• This gives the tea field an appearance of uneven development.
• Mosquito bugs prefer moist conditions and mild temperatures.
• Mosquito bug populations are often higher under heavy shade.

Figure 1: A tea garden patch affected by Helopeltis

1.5.2. Symptoms of Red Spider Mite attack and it’s affect on the gardens:

• Mites are tiny animals like insects.
• Mites sucks the sap from leaves causing leaves to change colour, curl, dry up and even fall off.
• Among different types of mites, Red Spider mites are the most serious pest of tea and causes severe damage to the crop during the peak growing period.
• Red Spider mites are found on both sides of the leaves.
• They are concentrated along the central rib of the leaves.
• While feeding they do not move at all.
• Groups of spider mites often cover themselves lightly with cobweb of short strands of silk.
• That’s why they are called as Spider Mites.
• The spider mites are found underneath the silk, walking slowly on the leaf surface.
• Leaves with heavy mite populations often have many tiny white spots on the surface; they are empty sheds skin of mites.
• It sucks the sap of the tea plant and causes the older leaves to fall off that reduces photosynthesis.
• Under severe infestations the young leaves fall off that reduces the yield of harvested leaves.
• Takes a long time for the tea plants to recover after the severe damage.

Figure 2: Leaves damaged by Red Spider (TRA Lab)


Figure 3: Red Spider Mites       Figure 4: Damaged leaf of a Red Spider Mite


Figure 5: A Garden Patch Showing Both Helopeltis and Red Spider Mite Attack

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