The following points highlight the twelve major pests occurring in India. The major insect pests are: 1. Scirpophaga (syn. Tryporyza) Incertulus (Walker) 2. Nilaparvata Lugens 3. Sitophilus Oryzae 4. Tribolium Castaneum 5. Tanymecus Indicus 6. Apion Corchori 7. Anomis Sabulifera 8. Leucinodes Orbonalis 9. Trlchoplusta ni 10. Helopetis Theivora 11. Termite 12. Bandicota Bengalensis.
Insect Pest # 1. Scirpophaga (syn. Tryporyza) Incertulus (Walker):
Scirpophaga incertulus (Fig. 1.1) is commonly-known as yellow stem borer of paddy. They thrive only on paddy plant, so they are called monophagous pest.
Distribution:
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In India, this is a major pest in Andhra Pradesh, Orissa, Tamil Nadu and West Bengal. This is widely distributed throughout the oriental region.
Morphological Features:
(a) Egg:
The freshly laid eggs are oval, flattened and pearly white in colour, which become darker and turn brown at the time of hatching.
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(b) Larva/Caterpillar:
The tiny (1.5 mm) newly hatched caterpillar is white in colour and black headed. They bear powerful mouth parts for boring the stem. When fully grown they measure about 20 mm and are dirty white or greenish yellow in colour, having brown coloured head and pronotum.
(c) Pupa:
The full grown larva stops eating within the stem and covers itself with fibres secreted from their own saliva. These fibres are deep grey in colour and 11 mm to 12 mm in length.
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(d) Adult:
The adults have a wing expanse of 25 to 45 mm and the wings are yellowish white with orange-yellow coloured apical margin. The female moth is bigger than the male and has a centrally situated black spot on each of the fore wings. The female have a prominent tuft of brownish yellow silken hair at the tip of their abdomen.
Life History:
In India this pest is active from April to October and hibernates from November to March as a full grown larva in rice stubble. Pupation starts sometime in March and the emergence of moths begin in April. The adult moths become active after dusk, when they mate.
The female lays about 120 to 150 eggs in 2 to 5 clusters on the underside of the paddy leaves. The eggs are covered with yellowish brown hair of the female tuft. They hatch in 6 to 7days. The caterpillars come out and start boring the stem and enter into the stem. Within the stem they feed on the plant tissues.
The larval period lasts for 20 to 30 days passing through six stages of different instars. After larval stage they pupate inside the attacked plant stem. Before going to pupation it constructs an emergence hole on the stem for the future adult. This emergence hole is always located above the water level. Within 9 to 12 days the pupa emerges out as an adult moth. The life cycle is completed within 31 to 46 days.
Mode of Damage:
The caterpillar alone is destructive. They start boring into the stem of the paddy plant downwards up to the root causing destruction of the pith. This makes the stem hollow and causing dead heart of the central shoots, which easily comes off when pulled.
The plants attacked in early stages dry up altogether but when infection occurs during flowering stage, the ear heads dry up and grains are not formed. This is known as the white ear heads.
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Control Measure:
(a) Cultural Process:
As this pest is monophagous, alternative cultivation of paddy and other crops will prevent the stem borer to continue its generation.
(b) Physical Process:
(1) The removal and destruction of stubble at the time of the first ploughing after harvesting the crop is necessary. It decreases the chances of carry-over to the next crop.
(2) Light attracts this pest — therefore, light trap can be used to kill the adults.
(c) Chemical Process:
(1) The spraying of 0.08% Methyl parathion, 0.05% Phosphamidon, 0.6% Diazion granules in the paddy field after 20 to 30 days of interval can control the pest.
(2) Fumigation by methylamide or calcium cyanide gives good result.
Insect Pest # 2. Nilaparvata Lugens:
Nilaparvata lugens (Fig. 1.2) is commonly known as brown plant hopper.
Distribution:
These are highly harmful in the paddy field of Korea, Japan, China and several countries of Southeast Asia. In India this pest infest high yielding variety of paddy plant. It is common in Punjab. Uttar Pradesh, Madhya Pradesh, West Bengal, Orissa and Andhra Pradesh.
Morphological Features:
(a) Egg:
Cylindrical greyish eggs possess two black spots. Eggs can be seen in clusters on the leaf. Incubation period of the egg is 4 to 11 days.
(b) Nymph:
Typical miniature insect like nymph bears all the characters of an adult, except reproductive organs. These nymphs are deep brown in colour. Nymph possesses five instar stages; each stage is slightly larger than its previous stage.
(c) Adult:
Blackish grey insect is 3.4 to 4.5 mm in length. Eyes are reddish in colour. The adults possess grey wings with black vertical lines. Sexual dimorphism is present. Adult males are larger in size than females.
Life History:
Generally adults stay in group near the base of the paddy plant. Adult Nilaparvata becomes active during the month of August and September in India. Females lay numerous eggs in cluster on the leaf of the paddy plant. There are as many as 124 to 158 clusters at a time.
A female insect generally lays about 680 eggs in its lifetime. The incubation period of the egg is 4 to 11 days, depending upon the atmospheric temperature and humidity. After incubation period nymphs come out and start eating the paddy leaf. The nymph completes its five instar stages by 18 to 35 days.
After completion of every instar it moults and during the whole nymph stage it moults five times. The nymph period varies upon environmental temperature — during hot period the moulting occurs rapidly. After nymph stage (fifth instar) the adult comes out and become sexually mature within 5 to 10 days. The adult female immediately lay eggs after copulation under favourable conditions.
Mode of Damage:
Adult and nymph both are harmful to paddy plant. They suck cell sap from the leaf and gradually the leaf becomes colourless and yellow. The paddy plant attacked by brown plant hopper becomes weak and its height becomes small. In favourable condition they can cause minimum 10% to maximum 70% destruction of the crop. Moreover, this pest is the agent of transmitting grassy stunt virus of the paddy plant.
Control Measure:
(a) Nursery Treatment:
Spraying of 0.03% Endosulphan 35E or 0.03% Phosphamidon 100EC or 0.03% Phenthion 20EC at the rate of 500 litres per hectare after 15 days of rowing gives good result.
(b) Treatment after Transplantation:
Before transplantation, 3% Carbofuran or 10% Phoretat at the rate of 10 to 15 kg/hectare should be mixed in the soil. Then, 7 days after transplantation 0.05% Phosphamidon at the rate of 700 litre/hectare should be sprayed. Again after 45 .to 65 days same spray at same rate will completely remove brown plant hoppers from the field.
(c) Light Trap:
This physical method can remove adult brown plant hopper to some extent.
(d) Cultivation of Resistant Variety:
Ptb-33, Ptb-21, ARC-6650, HR-1523 varieties of paddy are resistant to brown plant hopper.
Insect Pest # 3. Sitophilus Oryzae:
Sitophilus oryzae (Fig. 1.3) is commonly known as rice weevil.
Distribution:
It is found worldwide. In India it is found in all the states. It is probably the most destructive pest of rice in store houses. These pests are strong fliers, and it has been reported to fly from the godown to the field in vicinity, where it begins to infest the grain in field.
Morphological Features:
(a) Egg:
White coloured oval egg is laid in the pore made by the female in the rice grain. The egg is soft and plastic enough to fit into the cavity. A single female lays about 400 eggs in a breeding season. The eggs measure 0.6 to 0.7 mm in diameter.
(b) Larva:
The full-grown larva is about 5 mm in length. It is plump, fleshy and legless creature. Larva is with white body and yellow brown head.
(c) Pupa:
The pupa at first is dirty white, but later on becomes dark brown.
(d) Adult:
The adult is a small reddish brown beetle, about 3 mm in length. It possesses a cylindrical body and a long, slender curved rostrum. Its elytra or upper pair of wings are hard and bear four light reddish or yellowish spots. The thorax is marked with round depressions. The metathoracic wings are very well developed.
Life History:
Breeding period of this pest is from April to October. The adult hibernates in winter inside the cracks and crevices of the store house. During breeding period, the female makes a depression on the grain with the help of their mandibles and lay eggs in it. One egg is laid in one grain. After egg laying the hole is sealed with a gelatinous secretion. A single female may lay as many as 400 eggs in a season.
The eggs hatch in 6 to 7 days and the young larvae bore directly into the grain. They feed voraciously on the starch material of the rice grain but the shell of the grain is kept intact. At the end of the larval stage they become covered by a covering, called puparium inside the rice grain.
The pupa stage starts with the cessation of eating. The pupa stage persists for 6 to 14 days to become an adult. On emergence, the adult weevil cuts its way out of the grain and lives for about 4 to 5 months. The weevil completes 3 to 4 generations in a year.
Mode of Damage:
Both adult and larva cause damage to rice grains. In store house the weevil causes heavy damage to rice. They make the grains hollow and unsuitable for human consumption. Not only rice they also damage other grains like wheat, maize and sorghum grains particularly in monsoon. It has also been reported to feed on oats, barley, cotton seed, linseed and coca. The weevils spoil more than what they eat.
Control Measure:
The weakest point of the life history of this pest is that it is unable to breed in the grain if the grain moisture content is less than 9%. Therefore, keeping the grain in dry condition is the best way of controlling the pest.
If keeping the grain in dry condition is not practicable, then fumigation is the other alternative proposition as soon as the infestation reaches an intolerable level. The common fumigant used is methyl bromide, ethylene bromide, ethylene dichloride, carbon tetrachloride, etc.
Insect Pest # 4. Tribolium Castaneum:
Tribolium castaneum is commonly called the red- rust flour beetle (Fig. 1.4).
Distribution:
This is a common pest worldwide of wheat-flour. The adults are active creatures capable of short flights but are mostly found concealed in flour.
Morphological Features:
(a) Egg:
The eggs are white, transparent and cylindrical in shape. The surface of freshly laid eggs is sticky and thus flour or dust particles easily adhere to them making a white cover.
(b) Larva:
The newly hatched larva is a yellowish white worm-like creature and measures about 1 mm in length. As it matures, it turns reddish yellow, becomes hairy and measures over 6 mm in length. Its head appendages and last abdominal segments are darker in colour.
The larvae are negatively phototactic and are always found hidden in the flour. The infested flour becomes greyish and mouldy, so the pests are commonly known as red-rust flour beetle.
(c) Pupa:
The pupa has a yellowish and hairy worm-like structure.
(d) Adult:
The adult is a small reddish brown beetle, measuring about 3.5 mm in length and 1.2 mm in width. Its antennae are bent and bear a distinct club, formed by the three enlarged terminal joints. The last antennal segment is transversely rounded.
Life History:
The beetle passes winter season as adult and breeds during April to October. During breeding season, the adults copulate one or two days and then females lay eggs in the flour. A female can lay 300 to 900 eggs in a season. The incubation period lasts for 4 to 10 days.
After hatching, worm-like larvae come out. They eat the flour voraciously and undergo 6 to 7 moultings. The larvae become full grown in 22 to 25 days in favourable temperature of 30°C. At the end of larval stage they stop feeding and make a puparium in the flour with the help of salivary secretion.
Pupation takes place in the flour and the stage lasts for 5 to 9 days.
The development period from egg to adult is 26 to 30 days in summer, but is longer under unfavourable conditions of temperature and food.
Mode of Damage:
Both the larva and adult cause damage to the flour, flour products and also to the grains damaged by other pests. The insect is incapable of feeding on healthy and sound grain. The greatest damage is made during the hot and humid monsoon season. In severe infestation, the flour turns greyish and mouldy and has a pungent, repealing odour making it unsuitable for human consumption.
Control Measure:
The pest is unable to breed in the flour if the moisture content of the flour is less than 9%. Therefore, keeping the flour in dry condition is the best way of controlling this pest.
The other way of controlling the pest is fumigation before storing the flour in the godown. The common fumigant used is methyl bromide, ethylene bromide, ethylene dichloride, carbon tetrachloride, etc.
Insect Pest # 5. Tanymecus Indicus:
Tanymecus indicus, commonly known as ‘gujhia weevil’ (Fig. 1.5) is a very common wheat pest.
Distribution:
In India, the most serious pests of the wheat crop are the termites. Among other pests which have caused concern to cultivators in some areas during cultivation, is Tanymecus indicus. It causes great concern in Uttar Pradesh. In recent years it has also been reported from Punjab, Madhya Pradesh, Assam, Bengal, Tamil Nadu and Maharashtra.
Morphological Features:
Egg:
The eggs are whitish, oval and compressed in appearance.
Larva:
It is whitish in colour with blackish head. The body is smooth and flabby.
Pupa:
Pupa is initially greyish in colour. Later it becomes darker as development proceeds.
Adult:
It is a small blackish weevil, 4 to 8 mm in length and 2 to 3 mm in wing span. Their fore- wings are oblong and hind-wings are more or less triangular in shape. Mouth parts are light brown and are concealed beneath the head.
Life History:
The adult remains active from June to December. They pass rest of the year as pupa in the soil. The adult becomes sexually mature during October. They mate frequently and lay 65 to 75 eggs in 5 to 10 installments. The weevil lays eggs in the soil under the clods or in crevices in the ground. The eggs hatch in 6 to 7 weeks.
The larvae enter the soil where they feed on soil humus. The larva attains full growth at about 10 to 18 days. After that they pupate in earthen chambers constructed in the soil at the depth of 15 to 60 cm. Pupa stages are spent in the soil for 7 to 9 weeks.
The adults emerge next year in June. Only the adult stage causes damage to the aerial portions of the plant. Sometimes adults are also found lurking below clods of earth. The pest has only one generation in a year.
Mode of Damage:
It is a polyphagous pest attacking wheat, barley, gram, pea, poppy, maize, rice, etc. Its severe epidemic nature has often resulted in re-sowing of various crops.
The insects damage the roots of the wheat plants both during larval and adult stages. They cut the seedlings at or below the soil surface. The damage is particularly grave during October and November when the Rabi crops are germinating.
Control Measure:
Soil Treatment:
Treatment of soil with persistent insecticides should be made. At the time of sowing, application of Aldrin, Heptachlor or Chlorodane dust at the rate of 20 kg per hectare are useful to protect the crop.
Dusting:
The crop should be dusted with 5% BHC at the rate of 15 to 20 kg per hectare, when adult weevil can be seen.
Insect Pest # 6. Apion Corchori:
Apion corchori (Fig. 1.6) is commonly called as jute Apion or stem borer weevil (snouted beetle). They hamper the quality and size of the jute fibre.
Distribution:
It is recorded from all the jute growing regions of India and Bangladesh. In India, the States of West Bengal. Assam and Bihar are large scale producer of jute.
Morphological Features:
(a) Egg:
The oval egg measures about 0.43 mm in length and 0.33 mm in breadth.
(b) Larva:
A full grown larva is about 2.85 mm in length and 0.98 mm in breadth.
(c) Pupa:
It measures about 2.07 mm in length and 1.08 mm in breadth.
(d) Adult:
The small weevil is 1.8 mm in length and 0.8 mm in breadth with a very conspicuous snout. The adult stem borer weevil is brown or dull black in colour and possesses small whitish setae on its body. Its life span is usually 120 to 200 days.
Life History:
During April to June the weevils make holes with the help of its powerful rostrum in the apical part of the stem. The base of the petiole is generally the favoured site of making a hole. The female weevil lays eggs in the hole.
A single female may lay as many as 675 eggs during its lifetime. The egg laying stage during optimum condition is usually three days. The larvae emerge after 3 to 5 days and start feeding on the surrounding tissues.
The larvae become full grown at about 8 to 11 days. Then they make a rough chamber in the stem and pupate. The pupal stage is completed in about 4 to 6 days. The adult weevil emerges from the pupal chamber through an exit, which is either made by the larva before pupation or by the adult weevil itself. The life cycle is completed in 15 to 24 days.
A number of overlapping generations are completed during the jute season. The adult stage during winter, seeks shelter in bushes, shrubs and hedges. It starts laying eggs on the new crop in the next year. Therefore, the fields during winter are less attacked.
Mode of Damage:
Both adult and larva damage the quality of the jute fibre. The adult females bore holes with the rostrum for oviposition, in the jute stem and the larvae feeding inside the stem also destruct the fibre. A female may make a number of holes before laying eggs and thus damage numerous stems in her lifetime.
The larva, on hatching, begins to feed on the surrounding tissues that generally damage the fibre. Where such damage is excessive, the shoot above this point withers and a number of side branches are formed. Such plants yield short fibres of poor quality. If the attack occurs at the seedling stage, the whole plant succumbs.
The quality of the jute fibre deteriorates very much due to a number of reaction changes brought about at the site of injury. A mucilaginous substance oozes out of the site of damage and it firmly cements the adjacent tissues with the insect’s excreta into a hard structure, which is very resistant to the retting process.
Further, a kind of corky tissue develops around the wound, which actually represents the plant’s reaction to localize the injury. During this process the fibres get cemented with a good deal of surrounding tissues into a kind of knot.
During late period of infestation the basal portion of the plant becomes injured. The whole of the bark is found riddled by the grubs, resulting in a hard compact mass, with the bark sticking to the fibre. All these deformities resist retting so much that even after prolonged processing, when the fibres are washed, they are found to be either actually knotty or at least specky.
Control Measures:
Cultural Measures:
The damage in the apical portion is comparatively less in late-sown crops, mainly because from July onwards the weevil prefers to oviposit in the basal region.
Nitrogenous manures increase infestation but potash and phosphate fertilizers decrease the same.
Mechanical Measures:
The pest may be controlled by the removal and destruction of infested plants at the time of thinning the crop and by collecting and destroying the stubble after harvest.
Chemical Control:
In case of severe infestation a number of powerful persistent contact insecticides are now available, like 0.03% Methyl Parathion for grubs or 0.02 % Endrin for adults. But strong contact insecticides have a long residual effect.
Insect Pest # 7. Anomis Sabulifera:
Anomis sabulifera (Fig. 1.7) is commonly known as semilooper of jute and are considered as a major pest of jute.
Distribution:
This pest has been recorded from all the jute growing parts of India, Bangladesh, Sri Lanka, Burma and Africa. Among the states of India, West Bengal, Assam and Bihar are large scale producer of jute and this pest is a regular visitor in these states.
Morphological Features:
(a) Egg:
The eggs are small, transparent and have the appearance of a water droplet.
(b) Larva:
The larva of semilooper is green in colour and easily hides over the green leaves of the jute plant. Its head is slightly yellowish in colour. The elongated larva moves with loop like formation, hence it is called semilooper. The loop is formed because its five pairs of sucker feet are not well- developed, and when it moves it humps its back into an arch like structure.
There are small warts over its dorsal side and the lateral sides possess yellow stripes. Each segment bears short hair on small white ringed black papillae. The full grown stage attains a length of 4 cm.
(c) Pupa:
The pupa is inactive, soft bodied and brownish soil like colour. It is found naked in the soil as no pupal chamber is formed. The larva shrinks to about 3 cm in length at the end of pupal stage.
(c) Adult:
The adult has a typical moth like structure. The wings are yellowish in colour, with black spots. The females are larger than males. These moths are not visible during day time but come out after the sun sets.
Life History:
The moth passes winter in soil, in the pupal stage – this phenomenon is called diapause. They become adult during May and June, when the crop begins to grow in the field. Females lay eggs singly on the underside of the young leaves. There may be several eggs in one leaf.
A female can lay 150 eggs in a month. The egg stage lasts for two days, after which a small green caterpillar hatches out with three pairs of tiny sucker feet. Subsequently fourth pair of legs develops. The fifth pair of legs is not well developed and in this region a hump is formed during movement.
On emerging from the egg, the larva starts feeding on the apical soft leaves and buds. The larva attains full length at about 17 days after five moults.
Before the last moult the larva generally goes down to the soil, where it usually pupates. The pupation may take place on the soil or on the plant. In summer, the pupae emerge in about a week, but those, which diapause, spend the entire winter in that stage. The life cycle is completed in about one month and several generations are completed in a year.
Mode of Damage:
The attack is severe on half grown plants of one metre high. The infestations come about in three successive waves of which the middle one is the most damaging. During this wave about 90% of the leaves are eaten up.
The apical buds of the plant are most vulnerable and the intensity of infestation tends to vary inversely with the age of the foliage. Because of the green colour of the larva it is very difficult to identify the larvae on the leaves.
But the holes and the marginal cuts of the leaves give a characteristic appearance to the foliage and presence of these symptoms is sure indication of the infestation. Due to heavy infestation the plant growth is adversely affected, resulting in a considerable reduction in the yield of the fibre.
Control Measures:
Mechanical Measure:
Thorough ploughing after harvesting gives good result of destruction of pupa.
The caterpillars can be dislodged into kerosenized water by drawing a rope across the young jute plants.
Chemical Measure:
Spraying of Endosulphan (0.075% in 1000 ml water) or 0.075 % Phosalone in 1000 ml water gives good result. During heavy infestation, spraying of 0.075 % Endosulphan in 500 ml water is prescribed.
Insect Pest # 8. Leucinodes Orbonalis:
Leucinode orbonalis (Fig. 1.8) is a pest well known as caterpillar pest of brinjal.
Distribution:
This pest is widely distributed in Malaysia, Burma, Sri Lanka, India, Pakistan, Germany and East Africa.
Morphological Features:
Elongated in shape and scaly in nature.
(b) Larva:
These are creamy white when young and light pinkish violet in colour when full grown. They measure about 18 to 23 mm in length.
(c) Pupa:
The pupa stage is passed hidden in the fallen leaves in an inactive state. A silky cocoon is formed among the dry leaves.
(d) Adult:
This is a white moth. The dorsum of the thorax and abdomen has pale brown or black spots. The wings are white with a pinkish or bluish tinge and are ringed with small hair along the apical and anal margins. There are black, pale and light brown markings on forewings. The adult moth measures about 20-22 mm across the spread wings.
Life History:
The moth appears during March and April. The female lays elongated eggs singly or in batches of 2 to 4, generally scattered on the leaf surface. Each female can lay 150 eggs in its lifetime. The eggs hatch in about 3 to 6 days. The tiny larvae immediately enter the brinjal tissue by making a small hole on the surface. The larvae matures through five stages. The larval period varies within 9 to 28 days.
The full grown larva leaves the fruit to pupate in some comparatively dry area. The cocoon is tough and silken, mingled among the fallen leaves. The pupal period is generally 6 to 17 days. The life cycle is completed in 20 to 43 days during active season. The adult survives for only few days.
The pest continues its successive overlapping generations, depending on the environmental conditions, without any obligatory diapause. There may be five overlapping generations in a year.
Mode of Damage:
The damage is done by caterpillars. The tiny larvae enter into the fruit by making a tiny hole, which is not easily noticeable. It harbours within it and destroys the whole internal tissues. A healthy looking brinjal may contain several larvae. When these larvae enter the leaf petiole or young shoot, the infested portion wilts and droops.
Control Measure:
Precautionary Measure:
Special precaution is necessary to avoid the infestation of the brinjal pest. Uprooting and burning of the old brinjal plants, harbouring the borers, must be made before planting the new plants. These infected old plants would otherwise carry the infection from crop to crop and season to season.
Chemical Measure:
Insecticidal application can be expected only to check further infestation and not to kill most of the borers, which have already entered the plant tissues. The chemical control should be resorted to only when the initial precaution has been overlooked or when infestation by sap-sucking bugs or the Epilachna beetle is also involved.
The best course is to keep watch in the early stage of the crop when attack on the young shoot can be easily spotted and should be nipped in the bud.
Natural Measure:
There are some parasitoids associated with the larvae of this pest, they are —Pri- stomerus testaceus, Cremastus flavor bitalis, Bracon sp., Shirakias choenobii and Iphiaulax sp. etc.
Insect Pest # 9. Trlchoplusta ni:
Trichoplusia ni (Fig. 1.9) is a moth pest, commonly called as cabbage semilooper. It is a minor pest of cabbage.
Distribution:
This pest is recorded throughout India. It becomes major pest in northern states of India. Actually this is a polyphagous moth. It can also attack cauliflower, sunflower, and groundnut plants.
Morphological Features:
(a) Egg:
Eggs are minute and brownish in colour. They are laid either singly or in cluster, on the inner surface of the leaves of the cabbage.
(b) Larva:
The larva is light green in colour and usually hides itself under the green leaves of the cabbage. The head is slightly blackish in colour. The elongated larva moves with loop formation, hence it is called semilooper.
The loop is formed because its five pairs of feet are not equally developed, so when it moves, it humps its back into an arch like structure. Each segment of the larva bears groups of short hair on the dorsal side. The full grown stage attains a length of 4 cm.
(c) Pupa:
The inactive larva, pupates either within the leaves of the cabbage or in soil. No pupal chamber is formed. The larva becomes stumpy and attains a length of 3 cm.
(d) Adult:
The adult has a typical moth-like structure. It is 40 mm in spread wing. The wings are whitish in colour and ringed with hair.
Life History:
This moth remains active during the month of October to February. The female lays eggs on the leaves of the cabbage. After 3 to 6 days the egg hatches into larva. Immediately after hatching the larva bores into the leaf leaving a mark of minute pore. They pass five instar stages to attain the full grown size.
It usually takes 12 to 14 days to complete larval stage. Then it pupates either in the folds of the cabbage leaf or in the soil. The pupa stage lasts for 6 to 7 days. The adult remains dormant during summer and cannot be traced.
Mode of Damage:
The semi looper larva eats the leaves of the cabbage making holes on the leaves. Thus they destroy the cabbage totally. Several caterpillars may attack a cabbage at a time. These caterpillar-attacked cabbages have no market value.
Control Measures:
(a) Mechanical Measure:
During initial stage of cultivation the semilooper larvae can be picked and destroyea mechanically. For this purpose cultivator must have experienced eyes.
(b) Chemical Measure:
50 EC Malathion or 1% Endosulphan may be sprayed over the field in every 10 days. However, well before the harvest, the chemical spray must be stopped.
Insect Pest # 10. Helopetis Theivora:
Helopetis theivora (Fig. 1.10), commonly known as tea mosquito bug, causes much damage to the tea plantation.
Distribution:
There are two species of this bug found in India. One species is H. theivora (Waterhouse) found in eastern India (West Bengal, Assam) and the other species is H. antonii (Signoret) found in South India.
Morphological Features:
(a) Egg:
Eggs are elongated white sausage like structure. Each egg has two fibre-like structures projecting out from the shell.
(b) Nymph:
Nymphs are wingless. Appendages are very long.
(c) Adult:
The adult bug is 6 to 8 mm in length, with powerful wings and a strong rostrum. The cephalothoracic region of the male bug is black and that of female bug is orange in colour. They fly during night and spread over the field. They hide under leaves during daytime and prefer hot and humid atmosphere.
Life History:
They are bivoltine bugs, lay eggs twice in a year— once in March, April and another in October, November. After copulation female bug lays eggs on the buds of the tea plant. They also lay on the axis or broken end of the branch of the tea plant. At a time nearly 500 eggs are laid by a female in batches.
During hot period hatching takes 5 to 15 days time while in winter it may take maximum 27 days. The newly born wingless nymph moults five times to become an adult. Therefore, the nymph passes through five instar stages during its development. The duration of nymph stage varies from two weeks in summer to eight weeks in winter.
Mode of Damage:
Both nymph and adult devours the bud, green leaves and new branches of the tea plant. They suck the cell sap by digging the plant parts with the help of powerful rostrum. Their salivary secretion destroys the soft plant tissues. The leaves become black, the branches become dry and ultimately shredded off from the main branch.
Control Measures:
Physical Process:
Everyday during dawn and dusk capturing of nymphs and bugs by hand net and killing them by fire is the best practice.
Chemical Process:
0.1% Malathion spray at the rate of 500 litres per hectare can give good result during breeding season.
Insect Pest # 11. Termite:
Termites (Fig. 1.11) are generally referred to as white ants. They are social insects and live in colony.
Distribution:
Termites are distributed in temperate and tropical regions. According to habitat they are of two types — wood dwellers and ground dwellers.
There are several species of termites. Kalotermes and Neotermes attack live woods, while Cryptotermes attacks dry woods. Odontotermes, Macrotermes, Hypotermes livein termitarium (Fig. 1.11 A) constructed by the worker on the ground.
Morphological Features:
Egg:
The eggs are elongated capsule like and grey in colour. Queen lays egg in special chamber.
Nymph:
These are miniature forms of apterous reproductive form. They possess one pair of antenna and small ill-developed compound eye.
Adult:
An adult termite is soft bodied, white or grey coloured insect. They possess head, thorax and abdomen. The head bears a pair of compound eyes and one pair of antenna. Mouth parts are well- developed for cutting and chewing. Abdomen consists of ten segments.
As in other social insects, there are three castes in the life cycle of termite – so their colony is called polymorphic colony. The three castes are — worker, soldier and reproductive castes.
The characteristics of the different castes are given below:
(a) Worker:
These are small wingless forms having strong and sharp mandible, suitable for boring woods. These are infertile forms, although developed from fertilized eggs. They protect and serve the colony to run smoothly. They take care of queen. Generally they prefer dark, cold places.
(b) Soldier:
Their head is large and hard. Cephalic appendages are developed for protecting the colony. Soldiers are of two types on the basis of the structure of mandible—mandibulate, with developed chisel-shaped mandible, and nasute, with degenerated mandible and developed rostrum.
They are developed from unfertilised eggs. They generally reside on the outer sides of the termite mound and fight with the external enemies. Nasute generally spray toxin on enemies through their rostrum.
(c) Reproductive Caste:
Drones or king or males and queens or females are the members of the reproductive caste. They only perform reproductive function for the colony. They are of three types on the basis of their reproductive capability.
(i) Macropterous Form:
They are primary reproductive castes. Their wings are large and extend beyond the abdomen. Body is covered by deep grey chitin. They have highly developed compound eyes. Males are developed from unfertilised eggs. The male and female macropterous forms are called primary royal pair.
(ii) Brachypterous Form:
They possess wings but it never extends beyond the abdomen. They resemble more or less the nymph stage. Body is light grey in colour. Eyes are present but not well- developed. The male and female brachypterous forms are called complementary royal pair.
(iii) Apterous Form:
They are wingless and minute in form. Eyes are absent. Body covering is soft and pale in colour.
Life History:
Macropterous forms are primarily responsible for reproductive function. The primary royal pair starts nuptial flight before mating. After nuptial flight when they return to the colony they lose their wings. Then they mate. They are generally monogamous. Queen starts laying eggs after mating. Usually queen lays 1000 eggs per day. Both fertilised and unfertilised eggs are laid by the queen.
Male are developed from the unfertilised eggs. Brachypterous and apterous forms do not go for nuptial flight. They mate only when macropterous forms are not sufficiently successful in reproduction. The number of eggs they lay is very few in comparison to that laid by macropterous form.
The larva comes out of egg after two or three days. Nymphs are developed from larva after first moult. After second moult the nymph becomes worker and after fourth moult soldiers are formed from the destined nymph.
Mode of Damage:
They attack any type of plant and plant product used by human being. A flagellate protozoon, Trycho- nympha, remains as symbiont in their intestine. This protozoa can digest cellulose which the termite ingests in their food.
Control Measures:
(a) Physical Process:
After harvesting the stubbles of the field should be burnt. Deep ploughing can destroy the termitarium.
(b) Chemical Process:
Before sowing 5% Endrin spray on the field will keep termite away.
Insect Pest # 12. Bandicota Bengalensis (Bandicoot Rat):
This vertebrate pest is commonly known as mole rat/bandicoot rat/lesser bandicoot (Fig. 1.12).
Distribution:
This rat is recorded from India, Sri Lanka, Myanmar, Indonesia, Bangladesh, Vietnam, Formosa, etc.
Morphological Features:
The dorsal surface of the rat is covered with thick course fur of greyish brown colour. The ventral side of the body is covered with greyish white fur. The tail i sometimes shorter than and sometimes as long as the body.
Habit:
This species commonly inhabits the fields of crop, vegetables and fruits. It is a fierce animal and grunts in anger. They are very good swimmers. The bandicoot rats are well adapted to adjust themselves everywhere because they are provided with highly developed sense of smell, taste, hearing and touch. Therefore, they keep themselves away from any type of danger.
They always move along a definite pathway. They identify their routes with the help of dark greasy marks left in their way. They are nocturnal and highly engaged i n collecting food. They stock the food grains inside the burrows for future when food would not be available. The home range of the males is greater than the females and varies from 50 to 100 feet from their burrow.
After harvesting of crops, in unfavourable climatic conditions, the rat starts migration from one field to another or one store to another.
Habitat:
They inhabit in a well-formed burrow in the field. The rats vigorously survey the field, position of crop and humidity of the soil, before making the burrow.
Rat Burrows:
Rats dig and live in underground burrows (Fig. 1.13). Burrows can be simply a chamber connected to the outside by a short tunnel, or can be a large complex of interconnecting tunnels, passages, and cavities. Burrows are not unchanging entities. Burrows grow, change, and fall into disrepair as their inhabitants dig new tunnels, fill in old ones, or stop maintaining certain sections.
In fact, the structure of a burrow system is related to the social relationships of the rats, who dig and maintain it. If the social structure of the group breaks down, the rats are no longer able to maintain a complex burrow system and it falls into disrepair.
Parts of a Burrow:
i. Entrance:
Usually placed in a sheltered and/or sloped location. May be sealed with cut grass or dirt.
ii. Tunnel:
Straight tunnel segments have a median width of 8.3 cm. This width allows only one rat to pass at a time. Straight tunnel segments have a median length of 29.8 cm. After that distance, a tunnel usually bends, ends in a nest cavity, splits into two tunnels, or dead-ends.
iii. Chambers:
Small chamber of varying size, median 18.5 x 22.1 cm, which could accommodate 7 rats. The smallest chambers could accommodate only 3 rats, the largest 11 rats.
Chambers can have several uses:
(1) Nest cavity: contains bedding material, used for sleeping and rearing young litters.
(2) Food- cache: used for food storage
iv. Nest:
Built in a nest cavity, it consists of shredded material and serves as a sleeping place. There are three kinds of nest:
(1) Pad: Simplest kind of nest consists of just a few flat objects (leaves, bits of paper) which elevate one rat above the floor.
(2) Cup- shaped nest: Larger nest made in a cup shape. Made with finer texture grass or shredded paper interwoven a bit to form the walls of the cup. The cup is lined with flat objects.
(3) Hooded nest: Organised nest in which the walls grow so high that they form a ceiling, and the nest becomes a hollow sphere with just one opening. These nests are sometimes built by mothers for litters, but tend to be rather rare.
Growth of a Burrow System:
Burrows are frequently started by a pregnant rat just before giving birth. Rats like to start burrows against vertical surfaces (e.g., a man-made wall), under flat surfaces (e.g., under a board placed on the ground), under overhead cover (e.g., shrub, overhanging concrete, raised man-made floors), on slopes, and near sources of food and water.
Dirt excavated from the initial tunnel is usually piled around the tunnel entrance in a burrow mound.
The initial tunnel usually ends in a nest cavity. After a few days, a second entrance is added by digging from below. This second hole has no excavated dirt around it and is called a bolt hole, and may serve as escape exits in case the burrow is invaded.
Later expansions of the burrow system follow this same pattern of tunnel/cavity/bolt hole. The second cavity often becomes a food-cache, and is added by the mother rat shortly before the young are weaned. This allows the young to start on solid food in the safety of their home burrow. Once established, these simple burrows serve as centres for the elaboration of extensive burrow systems.
Modification of the Burrow:
Rats prefer to keep a certain distance between themselves and the ceiling of the nest cavity. As the rat brings in nesting material, the rat finds itself closer to the ceiling than it likes, so it removes dirt from the roof and carries it out. Over time, the bedding gets soiled and the rat brings more bedding in, and the process is repeated. Eventually, the nest cavity approaches the surface and its thin ceiling collapses.
Rats seal entrances temporarily with cut vegetation. These seals are easy to remove or squeeze through. Lactating mothers, especially those who have just given birth, may seal burrows in this way.
Rats also permanently seal entrances with loose dirt and lumps of dirt pushed up from below. They are packed into place with the forefeet. They may also carry dirt out another entrance and pack it into the neighboring one which is being sealed. A rat may seal a burrow when it feels a draft and when it is of low social rank.
The seal of a low ranking rat may prevent higher ranking rats from coming in and harassing it. The burrows of low-ranking rats also tend to leak more, so such seals may help counteract such leaks.
Trail Systems:
Outside the burrow, rats tend to confine their movements to the same routes every day. Gradually, trails form on the surface.
The main aim of burrow formation is to make protection, favourable micro climate, storage of food and breeding facilities. The burrow of the rat also consists of different fauna and flora; such as earthworm, crickets, earwigs, beetles, ants, pseudo-scorpion, millipede, mites, etc.
Life History:
The rats start living in separate burrows after attaining maturity. The breeding period is in two seasons; one is March to May and another is August to October. At the age of 3 to 6 months they start breeding and gestation period lasts for 21 to 25 days. The female comes in heat after every 4 to 5 days for about 2 to 3 days and breeds commonly twice in a year coinciding with the maturity of the crops.
The female produces 8 to 10 young ones in a litre. Young one are hairless, reddish and with closed eyes. After two weeks from birth, their eyes open and thery generally begin to feed on grains after 3 weeks. The sex ratio generally found is 50:50. The life span of an adult female is longer than a male.
Mode of Damage:
The major damage is the consumption and destruction of crops and crop plants. It is found that a rat consumes about 10% of their body weight daily. Moreover, they destroy the crop by taking to their store chamber. It has been recorded that maximum storage was 5 kg in a chamber.
The burrows made by rats weaken the foundation of buildings, causes seepage in channels, damage railway tracks in yards, etc. They can cause fire by damaging electric wires.
There are about thirty two diseases of man and other animals that are known to be transmitted by rats. They are reported to carry 18 different kinds of lice, fleas, ticks and mites. Different types of viruses, bacteria, fungi, protozoa, nematodes, arthropods carried by the rats can cause several diseases like bubonic plague, typhus fever, infectious jaundice, rat bite fever, food poisoning, etc.
Control Measure for Pests:
A. Physical Measures:
The types of physical measures practised to control the rats are as follows:
1. Ultrasonic sound:
Ultrasonic sound emitter is introduced in the mouth of the burrow made by the rat. The charged ultrasound destroys the ear drums of the rats, which are ultimately killed.
However, the wide range use of ultrasonic waves in the field is under investigation, especially with reference to its effect on the farmer and high cost of this method for field use.
2. Electrocuting:
Sometimes iron fencing around the field are electrified, so that rats when come out of their burrows in search of food and move across the fencing gets electrocuted. This method proved useful when there are no rats inside the fenced area. This has the inherent danger of electrocution of men and animals. Such a device should not be suggested for highly populated countries.
3. Traps:
These are the traditional methods to catch the rats by various mechanical devices and kill them. The formations of traps are devised differently in different localities. But this method takes much time and man power, and is very difficult to apply in large field area. However, in small area, like house and small godown, this method may be applied. Traps may be divided into two categories: live traps and kill traps.
In live traps, rats are caught alive and then killed by immersion in water, whereas in kill traps, such as break-back guillotine, rats are immediately killed as soon as they come in contact with them. The basic principle of the trap is to allure the rats to move into the contrivances from which they will not be able to escape or in which they will be killed.
Some of the commonly used traps are described below:
(a) Bamboo bow and arrow trap (Fig. 1.14):
In this trap a triangular bamboo stick is fixed on the bunds, tracks and near the burrow of the rats. When the rats get in to take food, the bamboo sticks snap automatically, the rat is trapped and ultimately gets killed. It is very common in south India.
(b) Pot trap:
It is a round earthen pot containing a lid and wood pegs. The lid is adjusted in such a way on the ground that the pot falls on the lid when disturbed. The bait is placed on the lid and also inside the pot. The bait when disturbed falls on the lid and rat is trapped.
(c) Cage trap (Fig. 1.15):
It is made of wood/ wires. The door of the trap is provided with a long handle and two springs. It is kept open by engaging a curved wire on the roof of the box which is fixed at the end of the handle. On the other end of the curved wire the bait is kept hanging suspended inside the box.
As soon as the rat entering the box tampers the bait, the curved wire or hook gets detached from the handle of the door and the lid falls off. In one setting only one rat can be caught.
(d) Wonder trap (Fig. 1.16):
Wonder trap is a small wire made cage divided into two chambers. A smaller chamber with tubular narrow opening, through which the rat enters and a larger one connected with the smaller one through another tubular passage, whose floor is moveable.
This tubular passage allows the rat to pass only when the base of the passage is drawn downwards under the weight of the rat and the rat rolled down into the bigger chamber containing baits. The opening is covered by one way gate. Inside the cage baits are given. The rat enters inside the trap for the bait but cannot come out. In this trap more than one rat can be caught in one setting.
(e) Back-breaking trap (Fig. 1.17 & 1.18):
It consists of an iron plate having toothed edges pointing upwards at its distal end. A U-shaped striker of an iron wire is attached with a spring on which the bait is fixed. As soon as the rat disturbs the bait for feeding, the trigger is released, crushing the rat between the edges of the basal plate and retreating U-shaped striker. Only one rat can be killed at one time. Sometime wooden traps are also indigenously used.
B. Biological Measures:
The natural enemies of rat are cat, dog, snake, mongoose and a number of birds. They catch the rat actively and eat them up. Many offices and housekeepers keep cats for protection from rats. Snakes are traditionally regarded as the most effective predator of field rats and also of house rats. Among birds, kite, owl and hawk are active predators of the rats in the field.
In some countries rats are even eaten by human being. In the “Crush rats campaign” organised in Indonesia in 1964, Mr. D.N. Aidit was commander of that campaign. He suggested that the rats be consumed by human beings.
C. Cultural Measures:
The change in the sowing and harvesting period of crops and change in the pattern of storage of grains may help in rat control.
D. Chemical Measures:
Several chemicals of various nature, origin and action are applied to different rat population to control them. This type of measure has proved to be most effective in rat eradication.
Various forms of chemicals used for rat prevention are as follows:
(l) Fumigant:
The fumigants are sprayed into the burrow of the rat. The most effective fumigants for rat eradication are: calcium cyanide, carbon monoxide and carbon dioxide.
(a) Calcium cyanide:
This fumigant on contact with air or moisture, releases hydrocyanin gas (HCN), which is highly poisonous to rat. Ten to twenty grammes of fumigant should be pumped in each live burrow for optimum action. In rainy or cold season this operation should not be made.
At the time of operation one should avoid breathing the fumes, otherwise it will adversely affect the application himself. As it is harmful to applicator such application has been banned.
(b) Carbon monoxide:
It is comparatively less effective in action than calcium cyanide. It requires at least 5 minutes acting time for killing the rat. It is employed in rat burrow with the help of exhaust powered by gasoline motor.
(c) Carbon dioxide:
In the form of dry ice carbon dioxide is applied into the burrow of the rat. It is generally used in fumigating refrigerated warehouse, where low temperature is to be maintained to present food spoilage.
(d) Others:
Methyl bromide, ethylene di-bromide and aluminium phosphide are used as fumigant to control the rats in the field or in well-ventilated houses, but these should never be used in the bedroom.
(2) Attractant and repellent:
Saffron, kewra, lemon, etc. are attractants of the rats. Poison baits are mixed with these attractants to kill the rats.
Among the repellent, lauro-nitritite, actidione, cycloheximide, triphenyltin and malathion are considered good. But with these repellent rats are kept away for sometime only. So repellents are totally temporary measures of rat control.
(3) Chemosterillants:
Male and female rats are sterilised by feeding furadantin and colchicine respectively. Application of 0.25 gm furadantin and 0.001 gm of colchicine with the attractant give good result for sterilising the rat population. Cadmium chloride and glyzophorol (containing butandial- bismethanesulphonic acid estar) is recently introduced as rat steriliser.
(4) Rodenticides:
The Rodenticides are grouped into acute and chronic poisons. The common acute poisons are arsenic trioxide, barium carbonate, zinc phosphide, norbromide, thallium sulphate and sodium fluroacetate. The common chronic poisons are derivatives of caumarin and are anticoagulants, e.g.,Warfarin, Dethmore, Rata- fin and Racumin.