A STUDY ON THE TEA PEST AND

DISEASES OF TEA PLANTS IN

SOME PARTS OF UDALGURI DISTRICT,

ASSAMArchana Das, M.Sc

Asst Professor in Zoology,Tangla College, Tangla.

A STUDY ON THE TEA PEST AND DISEASES OF TEA PLANTS INSOME PARTS OF UDALGURI DISTRICT, ASSAM

Introduction

In tea production, the term pest can be defined broadly as any living organism, plant or animal, which causes damage to the tea plant by feeding on it. The pest damage in tea can often lead to a significant impact on productivity, although the magnitude of pest infestation varies depending on altitude, climate and cultural practices.

Despite crop loss, pest infestation also

adversely affects the quality of processed tea, for example: damage caused by sucking pests like thrips and mites leading to dull appearance of tea. Severe infestation of flushworm, thrips, mites and mosquito bug affects the flavour of made tea.

Tea like other agricultural crops is prone to attack by diseases. Disease can be explained as a condition of the plant involving abnormalities of growth or structure. The symptoms, or visible signs, of a disease can vary between minute changes in appearance to death of the whole plant. Disease causing pathogens are parasitic organisms that live in or on the host plant and cause the appearance of disease symptoms, a process called pathogenesis. Parasitic diseases are important because they are infectious. They can spread between plants, often rapidly and extensively and may produce epidemics. The severity of symptoms when judged visually is not a good indication of the importance of the disease. Some diseases may produce no immediately obvious symptoms in the field but cause substantial reduction in yield, whereas others produce very obvious symptoms, which have little effect on the productivity of the plant.

OBJECTIVE

The study was aimed at obtaining information on the tea pest prevalence in some tea gardens of Bhergaon sub-division of Udalguri district of Assam with reference to the plant diseases in those gardens. For this study, a sampling survey of three tea gardens of the district was carried out. The study shows that altogether four types of pests are found to affect tea plantations in the sub-division.

MATERIALS AND METHODSWith a view to study the pest prevalence and

diseases of Tea plants in different regions of Udalguri district of Assam, three tea gardens of Bhergaon sub-division of the district were selected. The random method was adopted to select the names of the gardens as samples of study. The list of tea gardens selected for study in the Bhergaon sub-division of the district is shown below in the table: 1

Table: 1 showing tea gardens selected for study in Bhergaon sub-division of Udalguri district, Assam

Name of the gardens Distance from Tangla Town (km) Appox. area of study

Bhergaon Tea Estate 8 km 410 hectares

Dimakuchi Tea Estate 12 km 390 hectares

Paneri Tea Estate 10 km 400 hectares

.

The primary data relating to the (a) pest attack on tea plantations and (b) diseases of the tea plants were collected during the period January, 2014 to March, 2014 through the following methods

a) Survey: Survey routes based upon endemic areas were identified during the period of infestation (Jan-mar, 2014). After that survey was undertaken at every 1 km distance initially at weekly intervals and thereafter at 10 days intervals in the selected gardens. Every day, a minimum of 5 spots were observed with the aid of garden laborers and local people.

b) Field scouting: Based on the results of surveys, field scouting was initiated for tea pests once in 3-5 days in the concerned gardens to observe pest occurrence with prior permission from the garden authorities and with the help of garden labourers.

c) Interviews: The managerial staff viz. manager and assistant managers were contacted personally to know about pest attack and diseases of tea plants in the gardens.

d) Questionnaires: Questionnaires were prepared separately for staff and field labourers.

RESULT AND DISCUSSION 

Tea gardens Pests affecting tea plantations

Bhergaon Tea Estate Tea green leaf hopper, Red spider mite, Shoot borer

Dimakuchi Tea Estate Tea green leaf hopper, Red spider mite, Shoot borer, Tea Aphids

Paneri Tea Estate Tea green leaf hopper, Red spider mite, Shoot borer

Table: 2. showing major tea pests affecting different gardens. (January to March, 2014)

From survey it was found that in all the ten tea gardens of Udalguri district, three pests namely Helopeltis, Red spider mite and Looper caterpillar are primarily found to affect the tea plantations. However, in Dimakuchi Tea Estate Aphids are also found to infect plantations. Major tea pests affecting different gardens during January, 2014 to March, 2014 are shown in the table: 2 and 3.

Table: 3 showing total number of gardens infected by various tea pests.

Tea Pest Gardens Infected No. of gardens infected

Bhergaon Dimakuchi Paneri

Tea green leaf hopper

√ √ √ 3

Red Spider mite √ √ √ 3

Shoot borer √ √ √ 3

Tea Aphids x √ x 1

A) Tea green leaf hopper:Tea green leaf hopper (Emposca flavescens) are most damaging to the

tea leaves. Both the nymphs and adults are found to be damaging. They suck sap from leaves and causes the leaves to remain dry and finally make it to fall off. Eggs are laid by inserting in the tissue of new tea buds and shoot, particularly in the internode. In one bud upto 7 eggs are laid.

Fecundity 100 eggs during her lifetime. Depending on the temperature, the eggs will hatch after 5 to 10 days, producing nymphs. There are five nymph stages. The total nymphal development period is 7 to 16 days being faster in warm weather condition. So, it takes from 12 - 30 days for leafhoppers to complete a generation. There can be as many as 10 generations in a year. The life span of the adults is 14 - 21 days; females in general live longer than males. 

Symptom and Disease: Nymphs are more damaging than adults. Due to intensive sucking the

affected leaves curl downwards; the margins become curved, then turn brown and gradually dry up. This typical symptom is called “Rim Blight”. The midrib and veins of affected leaves also show somewhat brownish discoloration. Photosynthetic activities is drastically reduced due to loss of chlorophyll, this coupled with imbalance in growth hormones results in stunted plant growth. Hoppers feeding marks appear small yellow spots. Under dry conditions the upper part of leaves dry out. The less seriously affected leaves may develop a purple colour.

TEA GREEN LEAF HOPPER

B) Red Spider mite :

Red spider mite (Oligonychus coffeae) is one of the most common tea pest found in the tea plantation of Bhergaon sub-division. In all the three tea gardens red spider mites were seen damaging the upper surface of the mature leaves. Spherical bright red eggs are deposited by the female on leaves at the rate 4 – 6 eggs per day. Three developing stages are found to occur six legged larvae. Elliptically shaped female body is broad & round at the posterior end and carries the large purple markings.

Symptom & Disease:

Infestation starts along midrib and veins and spreads to the entire upper surface of leaves. Affected leaves were found bronzed, dry and crumpled. Leaf surfaces become scraped in early stages. Appearance of holes on leaves is a major symptom of the attack.

RED SPIDER MITE

C) Shoot borer: Shoot Hole borer or Shoot borer (Xyleborus fornicates) are

found to be effective in the gardens in January and early February. As March approached, the shoot borer was found to be missing from the tea plantation. They are especially effective in winter months and therefore, popularly known as “winter moths”. They have an Incubation period of about 10 to 12 days. Larval period lasts upto 50days. Pupal period is 20-30 days.

The adults are small in size brown, reddish brown or black in colour, head is completely bending downwards with blunt end. Only the adult stage was found to be damaging. They makes holes on the roots and on the lower part of main stem. Caterpillar bores into the stem or branches to feed on the wood. In early stages of attack, young plants or braches show wilting.

Symptom & Disease:Yellowing of lateral branches is a symptom of the attack.

Small pin holes on main trunk can be seen. Sometimes oozing of some liquid material from the trunk is also observed. It causes severe crop loss in the tea gardens.

SHOOT BORER

D) Tea Aphids :

Tea Aphid (Toxoptera auranti) is a polyphagous species attacking tea and other host plants such as coffee, cacao, citrus etc. Colonies of aphids are seen on tender shoots of tea immediately after pruning. Leaves curl up and shoot growth is stunted. Yellowing and distorted leaves, stunted growth and an unsightly black sticky substance on the plant may mean aphid attack. Aphids feed on a wide range of plants, and in severe cases the plant fails to thrive. As they feed, they secrete a sticky substance, called honeydew, which quickly becomes infested with black sooty mold.

Symptoms and Disease:  Aphids feed by piercing-sucking mouthparts and cause

damage by sucking plant juices. However, the fact that they transmit virus diseases causes more damage than the direct feeding. Plants in shady areas are more vulnerable to aphid infestations. Leaves curl and crinkle and flower buds may harden, causing flowers to distort.

Tea Aphids

Conclusion

Tea like other agricultural crops is prone to attack by diseases. Disease can be explained as a condition of the plant involving abnormalities of growth or structure. The symptoms, or visible signs, of a disease can vary between minute changes in appearance to death of the whole plant. Disease causing pathogens are parasitic organisms that live in or on the host plant and cause the appearance of disease symptoms, a process called pathogenesis. Parasitic diseases are important because they are infectious. They can spread between plants, often rapidly and extensively and may produce epidemics. The severity of symptoms when judged visually is not a good indication of the importance of the disease. Some diseases may produce no immediately obvious symptoms in the field but cause substantial reduction in yield, whereas others produce very obvious symptoms, which have little effect on the productivity of the plant.

In our study we basically concentrated on the insect pests of tea. They were found to cause mainly two diseases in tea plants of these three tea gardens. They are:

1.Leaf diseases and 2.Stem diseases We did not find any Root diseases in these three

gardens.

Stem disease appears initially as a small dark brown lesion on the bark. As the lesion develops and enlarges in size, the bark and cambium are killed, and the necrotic area becomes slightly depressed. The canker lesions develop on the stem at the collar region or on the branches (Plate 8). Upper edges of the lesions are usually heavily callused, leaves on the branches girdled by the lesions turn yellow and ultimately the branches die. Infection of the bush, especially of the collar, leads to secondary attack by scavenging termites which causes further damage and sometimes results in plant death. .

Control: Cultural practices can reduce water stress and thus limit the development of the disease and minimize losses. As the disease is sporadic, the control is based on taking the following preventive measures: avoid planting tea in drier areas, planting plants with a well developed root system, irrigation, mulching, avoid injury to the plant when weeding or pegging, collar prune and removal of damaged branches and burning them is recommended

In Leaf disease, the affected leaves generally change their colour and become brown or bronzed. Leaves may dry out and curl. Leaf surfaces become scraped in early stages. Appearance of holes on leaves is a major symptom of the attack

Control: Biological control has been the most effective method of controlling leaf diseases. Natural enemies may be insects and mites, bacteria, protozoan, fungi, viruses, nematodes or even vertebrates such as birds and toads. Successful biological control requires that the pest population is reduced to levels well below the economic threshold but is maintained sufficiently high to allow the survival of the biological control agent.

Thanks