Learn about the pests of tea and its control.
1. Tea Mosquito Bug, Helopeltis (Heivora Water- House and H. Antonii Signoret (Hemiptera: Miridae):
This pest is widely distributed in southern India and has also been recorded in Sri Lanka, Vietnam and Indonesia. In Africa, another allied species, H. bergrothi Reuter is prevalent. This bug bears no relation to mosquitoes and the name ‘tea mosquito bug’ is a misnomer.
The female bug is orange across the shoulders and the male is almost black. Both nymphs and adults damage the plant by sucking sap from young leaves, buds and tender stems. Of the two species, H. theivora is more common in eastern India and H. antonii in southern India.
Life-Cycle:
The female bug lays up to 500 eggs in the buds and axils of the leaves or often in the broken end of the plucked shoot. The eggs are elongate, sausage- shaped, having two long unequal protruding filaments. They hatch in 5-27 days, depending upon the prevailing temperature.
A freshly emerged nymph is wingless and on account of its long appendages looks like a spider. In summer, it completes its development in about two weeks after passing through five moults. In winter, the nymphal stage is prolonged to eight weeks or more. The adult is slender, 6-8 mm long, agile and a good flier.
It feeds at night on tea and several alternative host plants. During flight, the adults may be carried long distances by the wind and get dispersed over wide areas. Throughout the day, they are seen concealed on the underside of the leaves. The nymphs are parasitized by a nematode, Agamermis paradecaudate Steiner.
Damage:
The nature and extent of damage caused by various species of the genus Helopeltis vary a great deal. The attack of H. theivora in India and Sri Lanka is mostly on young leaves. The bug punctures the leaf frequently to suck the juice. While feeding, the saliva is injected and the tissues around the site of feeding are necrosed, becoming brownish or black.
By the coalescence of a large number of such patches, the entire leaf may become black and shrivelled, and may fall off eventually. A single bug is capable of destroying two shoots per day. In severe attack, causing defoliation, the shoots are killed and the plants appear like brooms.
The bugs prefer a moist, warm atmosphere and the tea bushes that provide this microclimate are preferred by the pest. H. antonii has a number of alternative host plants and damages the guava fruit, cashewnut and many medicinal plants in the Karnataka State.
Control:
(i) Collect nymphs and adults with hand nets early in the morning or in the evening and destroy them.
(ii) Spray the bushes with 500 ml of malathion 50EC in 500 litres of water per ha.
2. Bunch Caterpillar, Andraca Bipunctata Walker (Lepidoptera: Bombycidae):
The pest is widespread in India, Indonesia, Formosa and Vietnam. The larvae are gregarious and from the third onwards, they congregate on the branches of food plants during day-time. The brown moths have a wing span of 40-50 mm and the fore wings have wavy cross lines with two white spots near the outer margins.
Life-Cycle:
The female moth lays up to 500 yellowish eggs in linear clusters on the underside of leaves. The larvae emerge in about ten days and are light yellow. At first they eat up their eggshell and later on, they start feeding on the leaf tissues. The larvae pass through five instars and complete their development in 20-30 days.
The full-grown larvae descend to the ground and spin cocoons among dry leaves. The cocoons are noticed on the ground in batches. The pupal period is completed in 15-30 days. In the north-eastern region, the pest passes through four generations in a year.
Damage:
The caterpillars feed on leaves and are potentially a dangerous pest. The population of this insect fluctuates tremendously and is kept under check by a fly parasite and a bacterial disease which are spread easily owing to gregarious nature of the caterpillars.
Control:
(i) The pest can be suppressed by collecting the caterpillars manually and destroying them,
(ii) Spray 500 ml of malathion 50EC in 500 litres of water per ha.
3. Humped Slug Caterpillar, Spatulicraspeda Castaneiceps Hampson (Lepidoptera: Cochlidiidae):
This caterpillar is quite common on tea in Sri Lanka and India. It also feeds on castor and coconut leaves. The male moth is dark brown with bipectinate antennae and has a wing expanse of 15-17 mm. The female moth has chestnut brown fore wings and smoky black hind wings with a wing expanse of 20-22 mm. The full-grown caterpillars are small, dark brown or pale brown with a reddish band.
Life-Cycle:
The pest is active from June to September. The female moth lays 190-200 pale yellow and oval eggs on the under surface of leaves. The incubation period of eggs is 5-6 days. The young larvae start feeding on tender leaves. The larval stage is completed in 20-22 days.
The larva pupates in a broadly oval globular cocoon attached to the plant. The pupation is completed in 13-14 days. The duration of life-cycle from egg to adult stage ranges from 38 to 42 days. The larvae are parasitized by Apanteles sp. (Braconidae), Eucepsis sp. (Chalcididae) and Chrysis sp. (Chrysididae).
Damage:
The caterpillars mainly feed on the young leaves of tea which are the primary commercial product. Hence, the pest causes a significant damage to the crop.
Control:
Spray 625 g of malathion 50WP in 625 litres of water per ha.
4. Red Borer, Zeuzera Coffeae Nietner (Lepidoptera: Cossidae):
The pest is distributed in all the tea growing states. The moth is white with many small black spots on forewing’s and marginal dots on hindwings, and measures 28-40 mm across stretched wings. The full grown larva is purplish brown with brown head and measures 38 mm.
Life-Cycle:
The eggs are deposited in rows on the surface of leaves, cracks and crevices of the bark or even in the soil. The eggs hatch in about 10 days and the larva bores into the bark. The caterpillar tunnels down entering the main stem, reaching up to the tap root in young plants. The larva becomes full grown in 4-5 months and pupates within its tunnel for a period of 3-4 weeks. The emergence of moths takes place during April-May and August-September.
Damage:
Leaves of the attacked branches wither and the branches themselves die eventually. The attacked plants show pinkish excreta emerging out of the holes on the stem. Young plants when attacked are killed outright.
Control:
(i) Prune and remove the affected branches.
(ii) Chemical control measures are same as in case of red palm weevil.
5. Red Crevice Tea Mite, Brevipalpus Phoenicis (Geijskes) (Acari: Tenuipalpidae):
This mite is a sporadic pest of tea in India, Sri Lanka and Malaysia. It also attacks citrus, coffee, rubber, Phoenix spp., Grevillea, some medicinal plants and Parthenium hyterophorus. The adult is rather flat, elongate and oval. It is scarlet red in colour with black marks dorsally. It measures 0.3 mm in length.
Life-Cycle:
A female has been observed to lay up to 47 bright red, oval shaped eggs during an oviposition period of 40 days. The eggs are stuck firmly to the underside of leaves or in the crevices in comparatively young bark. They hatch in 6-13 days. The nymphs are flat-bodied, oval in outline and are scarlet in colour. The life-cycle is completed in 21-28 days. The predacius mite, Typhlodromus pyri Scheuten (Acari: Phytoseiidae) feed on different stages of this acarine pest.
Damage:
All active stages feed on the underside of leaves, especially along the midrib and the base. The loss of cell sap causes yellowing of the leaves. The bark and the leaf petioles of the affected shoots split turn brown and dry up.
Control:
Spray 1.25 litres of methyl demeton 25EC or 1.5 litres of dimethoate 30EC in 625 litres of water per ha.
6. Yellow Tea Mite, Polyphagotarsonemus Latus (Banks) (Acari: Tarsonemidae):
The yellow tea mite (broad mite) is widely distributed in tea and cotton growing areas of the world. In Asia, it is found in Bangladesh, India, Malaysia, the Philippines and Sri Lanka. In addition to tea and cotton, this sporadic pest also feeds on coffee, jute, tomato, potato, chillies, sesame, castor, beans, peppers, avocado, citrus, mango and rubber. The adult is yellow with white stripes on the dorsal side and is about 1.5 mm long.
Life-Cycle:
The male mites emerge earlier than the females. The latter lay oval but flattened eggs on the underside of the young flush of leaves. The eggs are arranged singly and they hatch in 2-3 days. The larvae are minute, white and pear-shaped which feed on cell sap. The larval and pupal stages last 2-3 days and the life-cycle are completed from 4 to 5 days. The female mite lives for about ten days, laying 2-4 eggs per day. The mite transmits a virus which causes leaf curl or ‘Murda’ disease of chillies.
Damage:
The mite is a serious pest in tea nurseries. The first two or three leaves and the buds are infested by this mite resulting in the browning of leaves. The shoot growth is also slowed down and production of the terminal tea-leaves is reduced very much.