Tea World

Lesson 21

Leaf and Shoot Pests

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The pests which infest the leaf and shoot are as follows:

(a) Mites (b) Helopeltis or Tea Mosquito bug (c) Caterpillars (d) Thrips  (e) Aphid (f) Jassids (g) Flush worm (h) Scale insects and mealy bugs and (h) Weevils and beetles.

Mites

Various species of mites belonging to the order Acarina, infest the tea. Mites are sucking pest. Mites are recognised generally from the colours of their body. Some of the mites are very small in size which can be seen only with the aid of a hand lens. The mites are perennial pests, a few of which persist on the bushes even when weather conditions become cold. They may also subsist on the alternate host plants which are many for every species of mite. Tea bushes are seen to be attacked simultaneously by more than one mite species.

Among different species of mites, Red spider mite (Olygonychus coffeae Nietner), Scarlet mite (Brevipalpus phonicis Geijskes), Pink or Orange mite (Acaphylla theae Watt (Keifer), Purple mite (Calacarus carinatus Green) and Yellow mite (Polyphagotarsonemus latus Banks)are economically important pests of tea. Another species of spider mite Tetranychus kanzawai Kishida is a serious pest in Japan and Taiwan.

Red spider mite (Olygonychus coffeae) is widely distributed in India, Bangladesh and Sri Lanka. In Africa, it is also a serious pest in Burundi, Kenya, Malawi, Uganda and Zimbabwe. It is also a common pest in Russia.

Red spider mite normally attacks the upper surface of the mature leaves. Infestation starts along the midrib and veins and gradually spreads to the entire leaf surface. In a severe attack, young leaves are also equally infested and they spread to the under surface of the leaves. They often form a web of silken threads and remain protected against adverse weather conditions.

Red spider mite is a sucking pest. The larvae, nymph and the adult suck cell sap of the mature leaves. Reddish or coppery spots develop on the sucking sites which subsequently unite to form large brown patches and defoliation may occur leading to huge crop loss.

Red spider mite prefers China type of tea. In India, it occurs throughout the year. This mite multiplies very rapidly in the early part of the growing season (February to May) when weather conditions remain relatively dry. During July, their population is greatly reduced due to heavy shower which washes away the mites. In winter also, the population is reduced.


Red spider infested tea

Red Spider Mites

The following factors favour the occurrence of red spider mite

  • Prolong drought favours the incidence,
  • Light rains with intermittent sunny days increase the mite,
  • Unshaded or poorly shaded areas suffer most,
  • Roadside bushes covered with dust favours the incidence,
  • Waterlogged areas are prone to red spider mite,
  • Unpruned or light skiffed tea bushes are more prone,
  • Weed infested areas suffer more.

Scarlet mite (Brevipalpus phonicis) is another harmful pest which has occasionally caused heavy loss of crop in different countries. It is the most widely occurring species in N.E. India, Bangladesh, China, Indonesia, and a number of African countries. Another species, Brevipalpus australis Tucker is predominant in South India and Sri Lanka.  Brevipalpus obovatus Donnadieu is the species of this mite which are seen to occur sporadically in Kenya and a few other countries of Africa.

Scarlet mite mostly feeds on the under surface of the leaf particularly around the petiole and sometimes prevents the flow of nutrients to the leaf lamina. Its sucking leads to yellowing of leaves and brownish discoloration of the mid rib. The bark of the affected stem may split. Severe infestation results in premature defoliation.

Purple mite (Calacarus carinatus)is another harmful mite common to Asia, USSR(CIS) and a few African countries. It is an active pest both in South India and N.E. India. Purple mite mostly occurs on the upper surface of mature leaves. The affected leaves turn purplish brown particularly at the margin, dry up and fall off.

Pink or Orange mite (Acaphylla theae) occurs in China, Bangladesh, Indonesia, Malaysia, Taiwan and USSR (CIS). In India, the mite is more prevalent in N.E. India and all tea growing districts of South India.

It attacks both surfaces of mature and young tender leaves. Petiole and tender stem may also be infested. Affected leaves turn pale yellow, leathery and curl upwards. It could affect young tea during cold weather.

The Yellow mite (Polyphagotarsonemus latus Banks), sporadically attacks the flush and the young leaves and causes damage in isolated patches in N.E. and South India. It is a serious pest in the nursery in East and South Africa, Mauritius and Malawi. Although it occurs on both surfaces of leaves yet is more abundant on the abaxial surface. It prefers cool, humid sheltered conditions and disappears with the onset of dry and hot conditions. The affected leaves become more dark and lose their natural gloss. The internodes become very short with many leaves arising out almost at the same point.

Helopeltis or Tea Mosquito Bug

Helopeltis, commonly known as ‘Tea Mosquito Bug’ belongs to the Order Hemiptera. The name Tea mosquito bug is a misnomer since Helopeltis comes under the order Hemiptera, while common mosquitoes belong to the order Diptera. The species   Helopeltis theivora Waterhouse is a serious pest of tea in N.E. India, South India, Bangladesh, Sri Lanka and Indonesia. Another species Helopeltis schoutedeni Reuter is a major pest in East Africa, Malawi and Cameroon. One more species, Helopeltis orophila Ghesq occurs as a minor pest in Uganda, Burundi and Zaire. There are some other species like H.bradyi, H.cinchona, H.clavifer which infest tea.

Helopeltis is a sucking pest. The tea mosquito bug (Helopeltis theivora) is one of the major pests which causes extensive damage in tea. In N.E.India, it is present almost throughout the year, but the peak period of infestation is from June to September. During winter, its population comes down and reappears from February-March.

The adult helopeltis is a tiny insect with a long antenna. The normal distance of flight is very less; it is only from one bush to another. However, high wind can carry the insect over long distances causing a sudden spread of attack. The females lay eggs in the tissue of tender stem, mid rib and the petiole of leaves.

The nymphs and adults of helopeltis are the active suckers of sap from buds, young leaves, tender stems and shoots. They feed at early morning, late evening and at night hours. On a sunny and warm day, they take shelter in the lower layer of the bush canopy. 

While sucking the sap, they inject toxic saliva which causes necrosis of the tissues surrounding the puncture .A circular spot is formed around the sucking point which turns brown first, then black and subsequently dries up. The badly affected leaves become deformed and even curl up. In a severe attack, the bushes cease to form shoots and the affected areas may not flush for a long period. The tender stems near the apex turn dark brown due to oviposition and the shoots die back. Cracking of the tender stem may also occur at the site of oviposition which results in callus growth underneath and the shoot dries up. Infestation of helopeltis may become destructive during the cropping season.

Caterpillars

Caterpillars feeding on mature leaves of tea form a large group of which only a few can be ranked as major pests.  Looper Caterpillar (Buzura suppressaria Guen), Bunch Caterpillar (Andraca bipuncata Wlk) and Red Slug caterpillar (Eterusia magniica Butler) are well known caterpillar pests of tea.

Looper Caterpillar (Buzura suppressaria) is a well known pest of tea in India and Indonesia. It is responsible for considerable damage in Assam and Dooars in West Bengal. The pests spread so rapidly by defoliating the bushes that control becomes difficult unless measures are initiated at the start of the attack.

The young looper is dark brown with pale greenish white lines on the back and side and has a brownish head. The body colour gradually changes to green to brownish grey or dark brown. The life cycle is completed in about 60-72 days.

Young caterpillars first eat out the young leaves making very small holes along the margin and then bite off small pieces at the margin of the leaf. The young early instars feed on the tender leaves while the late instars prefer older leaves. In severe cases of attack, caterpillars can completely strip a bush of its leaves and this may cause the infestation to become devastating within a short period. Young larva of looper is highly mobile and can, therefore, be carried to a long distance.

  Looper Caterpillar

Bunch Caterpillar (Andraca bipuncata) which can be easily recognized from the bright clusters formed on branches occurs in India, Bangladesh, Indonesia, China and Taiwan. This is one of the oldest pests recorded in tea which can cause serious trouble unless controlled in time. Destructiveness of this caterpillar increases as they grow in age.

Full grown Bunch caterpillar is about 65 mm in length with a brownish black head and the body is densely covered with fine hairs. It is tawny yellow with a reddish tinge and broad brown transverse bands running on each body segment crossed by a number of yellowish longitudinal lines.

Females lay in cluster on the under surface of leaves and occasionally on the stems and each cluster consists of a series of eggs arranged in rows. The life cycle is completed in 55-65 days in March-June passing through 5 larval instars in N.E. India

The young caterpillars remain in cluster on the undersurface of leaves during day hours and become active in the night and start feeding .The branches on which they form the clusters are completely stripped of the leaves; thereafter they migrate to the adjacent bushes.

  Bunch Caterpillar

Red Slug caterpillar (Eterusia magniica) occurs in many Asian countries including N.E. India but is not as harmful as the Bunch caterpillar.The other species Eterusia virescens Butler occurs in tea in South India and Eterusia singala Moore infests tea in Sri Lanka.

It is another serious caterpillar pest in N.E. India. Early instars of the caterpillars first eat out the leaf, making hole biting the edges. When they grow in size the whole leaf is damaged. In severe infestation the bushes may be completely striped of their leaves. Usually the caterpillar attacks the leaves but in a severe outbreak, the bark is also eaten away resulting in die back of the branches.

The caterpillar becomes full grown in four to five weeks during May–June. They are active usually during the early and later part of the day till night.

Thrips

Several species of thrips (Thripidae) infest tea and cause heavy damage by feeding on the buds, tender leaves and older tea under plucking. The tea thrips (Scirtothrips dorsalis) is a major pest in N.E. India, Japan, China and Taiwan. In India thrips cause considerable loss in tipping fields recovering from pruning. Continuous feeding of young leaves by adults and nymphs causes laceration of plant tissues. It sucks the cell sap which oozes out from the damaged leaf. Both the nymphs and adults cause damage to the tender leaves. The initial symptom of attack is light brownish discoloration of the tip and the basal part of   leaves. Latter on 2-4 sand papery layers appear on either side of the mid rib. Badly damaged leaves appear rough, deformed and curled and the shoot growth is retarded with the formation of corky tissues on the bark. Droughty spell encourages rapid build- up of thrips population.


Thrips

Thespecies Scirtothrips kenyesis Mound occurs in Kenya throughout the year. Another species,Black tea thrips (Heliothrips haemorrhidalis Bouche) is also a   serious pest in some areas of Indonesia, Kenya, Tanzania and Uganda. In Souh India, three different species of thrips viz, Heliothrips haemorrhidalis, Scirtothrips bispinosus and Haplothrips tenuipennis

Jassid

Jassid (Empoasea flavescens Fabr) is an insect pest of tea, commonly known as ‘green flies’. It occasionally causes serious damage to young and mature tea bushes in N.E. India, Bangladesh, Japan, China and Vietnam. Empoasea onuki and Empoasea formosana occur in Japan and Taiwan respectively.The nymphs and the adults of the insect (Empoasea flavescens Fabr) suck the sap of the young leaves and occasionally the tender stems of the growing shoots. Normally they attack the under surface of the young leaves. The growth of the affected leaves become uneven and the leaves usually curl downwards and the margin becomes recurved. The characteristic symptom is known as the ‘Rim Blight’.The growth of the infested shoot is arrested and the leaves remain stunted, dry up and eventually fall off.


Tea Jassid

The newly hatched nymph is a colourless insect with pink eyes, but soon after feeding it becomes slightly yellowish green in colour. The adult is a small yellowish green insect about 2.50 mm (male) to 2.75 mm (female) in length. Tea Jassids occur throughout the year but they are more active during March to July.

Aphid

The tea aphid (Taxopetra aurantii) is a common pest of tea and widely distributed all the tea growing countries.. The adults and nymphs of tea aphids suck sap from tender stems, buds, petioles and lower surface of the leaves along the mid rib. As a result of the loss of sap the leaves crinkle and curl inwards resulting in marginal necrosis in later stage.

The pruned bushes suffer the most from the aphids attack from February onwards.The insect multiplies rapidly resulting in a heavy build-up of colonies within a short time, but with the commencement of normal plucking the colonies are removed before significant damage can be done. It causes significant damage to the nursery plants.


Tea Aphid

Flushworm

Flushworm is a leaf tier pest of tea bush and a seasonal pest of India and Indonesia. The larva of the moth Cydea leucostoma Meyrickwhich attacks a few top leaves, tying them together, is commonly known as flush worm. The larva remains inside the fold of the bud or young leaf and feeds by scraping off the tissues of the upper surface, occasionally eating away the apical portion of the bud.

The affected leaf becomes rough, thick and somewhat brittle in texture, with a brownish discoloration of the damaged surface. The affected shoots cannot reach full development and the internodes are greatly shortened and the tender stem bends over as a result of binding of two or more leaves together.

In N.E.India, the pest appears from late February when new shoots start coming up. The peak of the attack is usually during March-April.

  Flush worm

Scale Insects and Mealy Bugs

Scale insects and mealy bug (Coccoids) are sucking pests which attack the foliage, stems and roots of the tea bushes. Over 30 species of scale insects and mealy bugs have been recorded from tea, out of which 12 are serious pests infesting leaves and tender stem. Some species of scale insects are permanent major pest of tea. Scale insects excrete honey dew and are attended by ants. In a prolonged attack, the bark dies and irregular swellings are formed on the stem. In a persistent attack, the bushes become so debilitated that they produce little growth for some years, and then the branches die back.

Mealy bugs are a group of insects of the family Pseudococcidae. They are covered by a powdery coating or waxy filaments. The infested shoots become unproductive leading to the dying up and fall of the leaf.


Scale insect

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