Ramesh Arora, Vikas Jindal, Pankaj Rathore, Raman Kumar, Vikram Singh and Lajpat Baja
Punjab Agricultural University Regional Station
Faridkot-151 203, India
Cotton fibre has exercised a profound influence on humans from time immemorial. With a history going back to antiquity, the fibre has maintained its pristine purity and importance to this day. In India, cotton crop has had the pride of place among cash crops from the earliest time. It finds mention in the Rig-Veda, the oldest scripture of Hindus. Cotton fabrics were found in the Mohen-jo-daro relics from the ancient Indus Valley Civilisation which flourished in India about five thousand years ago (Sethi et. al., 1960).
Even in modern times, cotton is a vital crop of commerce in India and is popularly known as ‘Whitegold’. With over 2500 textile mill units, about 1.5 million power-looms, 4 million hand-looms and thousands of garment, hosiery and processing units, the textile industry has grown up as the largest agro based industry in the country (Rajendran and Jain, 2004). Cotton contributes 14 per cent of the value addition in the manufacturing sector and provides employment to about 35 million persons. Textiles exports contribute 20 per cent of the gross export earnings of the country. It is in fact the only industry in the country which is self-reliant from the raw material to the highest value added products (garments).
India is the only country in the world where all the four cultivated species of cotton, viz. Gossypium arboreum, G. herbaceum, G. hirsutum and G. barbadenses along with intra- and inter- specific hybrids, are cultivated along the diverse agroclimatic conditions, varying from 8-32o N latitude and 70-80o longitude. The Asiatic or diploid cottons, G. arboreum and G. barbadenses (Egyptian cotton) were introduced in India by the East India Company during the nineteenth century. The cotton is grown in North, Central and South zones in India (Rajendran and Jain, 2004).
Important Insect Pests Damaging Cotton Crops in India
Cotton ecosystems throughout the world harbor a wide variety of insects. The number of species found in the crop may range from a few hundred to more than a thousand. The vast majority of these species are parasitoids and predators of phytophagous species. Estimates of the number of pests species range from 20 to 60 but significant damage is caused by 5-10 key pests in most production systems (Luttrell et.al.,1994). One hundred and sixty two species of phytophagous insects have been recorded on the crop in India, of which 24 species have attained pest status (Table 1.) and nine are key pests in one or more cotton growing zones of the country (Sundramurthy and Chitra,1992; Dhawan, 2000). The life history and damage symptoms for important insect pests are briefly described here (Atwal and Dhaliwal, 2001; Mathews and Tunstall, 1994; Simwat, 1994)
Sap Sucking Pests
Amrasca biguttula (Ishida) (Hemiptera: Cicadellidae)
Cotton jassid is the most destructive sucking pest of American cotton in the North Zone and is present throughout the country. Besides cotton it also feeds on okra, potato, brinjal and some wild plants. Adults are about 3 mm long and greenish yellow during the summer, acquiring a reddish tinge in the winter. The winged adults jump or fly away at the slightest disturbance and are also attracted to light at night. The female lays about 15 yellowish eggs on the undersurface of the leaves, embedding them into the leaf veins. The eggs hatch in 4-11 days and give rise to wedge-shaped nymphs, which are very agile. They suck cell- sap from the undersurface of leaves and pass through six stages of growth in 7-21 days. On transformation in winged adults, they live for 5-7 weeks, feeding constantly on the plant juice. The pest breeds throughout the year except during the winter months, only adults are found on plants such as potato, brinjal, tomato, etc. In spring, cotton jassid migrates to okra and starts breeding. The pest completes seven generations in a year.
Chrysoperla sp. (Chrysopidae) and spiders like Distina albida L. feed on nymphs and adults of the cotton jassid.
Both the nymphs and adults suck sap from the leaves. Injury to plants is due to the loss of sap and probably also due to the injection of toxins. The attacked leaves turn pale and then rust-red. With change in appearance, the leaves also turn downwards, dry up and fall to the ground. Owing to the loss of plant vitality, the cotton bolls also drop off resulting in yield reduction.
Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae)
Cotton whitefly emerged as a serious pest of American cotton after the introduction of synthetic pyrethroids during 1980s particularly in the dry areas. It also acts as a vector of the dreaded leaf curl virus disease. Apart from cotton, this insect also feeds on various other plants such as cabbage, cauliflower, mustard, melon, potato, brinjal and okra. The louse-like nymphs, which suck sap, are sluggish creatures clustered together on the under surface of the leaves and their pale-yellow bodies make them stand out against the green background. In the winged stage, they are 1.0-1.5 mm long and their yellowish bodies are slightly dusted with a white waxy powder. They have two pairs of pure white wings and prominent long hind wings.
The female lays eggs singly on the undersurface of the leaves, averaging more than 100 eggs per female. The eggs are stalked, sub-elliptical and light yellow at first, turning brown later on. They hatch in 3-5 days in April-September but take much longer during winter. The nymphs, on emergence, look elliptical and soon fix their mouthparts into the plant tissues. They feed on cell-sap and grow into three stages to form the pupae within 9-14 days in April-September. The pupae change into adults whiteflies in about 4 weeks. The life-cycle is completed in 14-122 days. The insect breeds throughout the year completing up to 11 generations.
Eretmocerus massii Silv. (Aphelinidae) is associated with nymphs and pupae, and incidence of parasitization reaches up to 33 per cent while Encarisa sp. is responsible for 5-10 per cent parasitization of nymphs and pupae. Chrysoperla sp. (Chrysopidae) and Brumus sp. (Coccinellidae) prey upon nymphs and adults.
The vitality of the plants is lowered through the loss of cell sap to the nymphs and adult whiteflies. In addition, normal photosynthesis is interfered with due to the growth of a sooty mould on the honeydew excreted by the insect. The attacked crop gives a sick, black appearance. Consequently, the growth of the plant is adversely affected and when the attack appears late in the season, the yield is lowered considerably. The whitefly acts as a vector of the cotton leaf-curl virus, which has spread, to large areas of the northern zone. Even low population of whitefly is capable of spreading the disease and must be controlled at the early crop stage to prevent spread of the disease.
Aphis gossypii Glover (Hemiptera: Aphididae)
Cotton aphid is a sporadic pest of cotton. It also feeds on potato, cucurbits, chilli and many ornamental plants. The apterous (wingless) adult is light yellow to light green, whereas alate (winged) form is brown in colour. The black cornicles are quite prominent. The pest breeds parthenogenetically and each female deposits about 20-50 nymphs. The four nymphal instars last for 7 to 10 days. The total life cycle is completed in 9 to 64 days with an average of 28 days.
Both young and adult cotton aphids suck plant sap. Infested plants become weak and the tender shoots, leaves fade gradually and may become blighted due to appearance of sooty mould on middle canopy leaves in case of severe attack. Dry conditions favor rapid increase in pest population and younger plants are more susceptible than the older ones.
Coccinellid beetles, Coccinella septumpunctata Linnaeus and Menochilus sexmaculata (Fabricius) are common predators of cotton aphid.
Thrips tabaci Linnaeus and Scirtothrips dorsalis (Hood) (Thysanoptera: Thripidae)
Cotton thrips are commonly found on cotton and vegetable crops. The adults are slender and yellowish brown. The males are wingless while the females have long, narrow wings. The pest breeds on cotton during May-September. The adult female lays 50-60 kidney-shaped eggs, singly into green plant tissue, at the rate of 4-6 eggs per day. The eggs hatch in 3-8 days. The nymphal stage lasts for 5-8 days and pupal for 2-4 days. The nymphs and adult thrips lacerate the surface tissues of the foliage and then feed on the exuding sap. The affected leaves curl and give silvery brown appearance. Prolonged dry spell during May-June often results in high build up of the pest on the young plants. In severe infestation, the seedlings shed leaves and may dry up.
Spodoptera litura (Fabricius) ( Lepidoptera: Noctuidae)
Tobacco caterpillar is traditionally a pest of cauliflower and cabbage crops in Punjab but in recent years it has caused damage to cotton crop in the northern zone. It is also sporadically recorded on castor, groundnut, tomato, sunflower, etc.
The damage is done only by the caterpillars, which measure 35-40 mm in length at maturity. They are velvety black with yellowish-green dorsal stripes and lateral white bands. The moths are about 22 mm long and measure 40 mm across the spread wings. The fore wings have beautiful golden and grayish brown patterns.
This pest breeds throughout the year, although its development is considerably retarded during winter. The female lays about 300 eggs in clusters. These clusters are covered over by brown hairs and they hatch in about 3-5 days. The larvae feed gregariously for the first few days and then disperse to feed individually. They pass through 6 stages and are full-fed in 15-30 days. The full grown larvae enter the soil where they pupate. The pupal stage lasts 7-15 days and the moths, on emergence, live for 7-10 days. The life cycle is completed in 32-60 days and the pest may complete eight generations in a year.
The larvae feed on leaves and fresh growth and are mostly active at night. In case of severe infestation the buds and bolls may also be attacked. In Punjab, severe attack on cotton crop is usually recorded in September-October. Whenever farmers use herbicides for the control of horse purselane (Trianthema monogyna Linn) which usually harbours the pest, it results in an outbreak of S. litura on cotton.
Sylepta derogata (Fabricius) (Lepidoptera: Pyralidae)
The cotton leaf-roller is widely distributed in the Orient and Africa. In India, it occurs in all the cotton growing tracks and is an important sporadic pest in the north zone. Besides cotton it has also been recorded on various other malvaceous plants including okra.
The caterpillar measures about 25-30 mm in length when full grown. The greenish grey or pink caterpillars are usually found feeding inside the rolled leaves. Moths are yellowish white, with black and brown spots on the head and the thorax. They measure about 28-40 mm across the spread wings and have a series of spots of dark brown wavy lines on the wings.
The leaf-roller is active from March to October and passes the winter as a full grown caterpillar among plant debris or in the soil. The hibernating larvae pupate by the end of February and the moths emerge during March. The moths are active at night and each female lays 200-300 eggs singly on the underside of the leaves. The eggs hatch in 2-6 days and the young caterpillars feed first on the lower surface of the leaves. The older larvae roll leaves from the edges inwards up to the midrib and feed on the tissues from the inside. The larvae grow through seven stages and are full-fed in 15-35 days. They pupate either on the plant, inside the rolled leaves or among plant debris in the soil. The moths emerge in 6-12 days and live for about a week. The life -cycle is completed in 23-53 days and the pest passes through 5 or 6 generations.
Trichogramma spp. atack the eggs while Brachymeria tachardiae Cam., Elasmus indicus Rohn., Gosyphus nursei Cam. and Trichospilus pupivora Ferrieri are associated with the larvae of this pest. The young larvae feed on the lower epidermis of the leaves while older larvae generally feed on leaf tissues inside the rolled leaves from leaf margins to the mid rib. If the infestation is severe, several rolled leaves are found drooping on a plant with the leaf petioles. The plants growing in shade on the margins of a field usually carry a higher infestation and may be completely defoliated.
Anomis flava (Fabricius) (Lepidoptera: Noctuidae)
Green semi-looper is widely distributed cotton defoliator found throughout the cotton growing areas of Asia, Africa and Australia. In India, it is a sporadic pest of cotton and sometimes causes a serious damage to the crop particularly in Gujarat and Rajasthan. Besides cotton, the larvae also feed on a number of other malvaceous plants.
The full grown larva is 25-30 mm long and is pale-yellowish green with five white lines arranged longitudinally on the dorsal surface. The adult is an attractive, small moth with reddish-brown fore wings traversed by two darker zig-zag bands. The hind wings are pale brown. The emergence of moths coincides with the warming up of the season. The female lays up to 600 eggs on leaves during an oviposition period of 8-12 days. The eggs hatch in 4-5 days. The larvae which move around with a characteristic semi-loop crawl and feed on leaves. They complete development by passing through 5 instars within a period of 18-20 days. They make a loose cocoon before pupation, either within the leaf folds or among debris in the soil. The pupal period lasts 8-9 days. The moth have a life span of 12-13 days and life-cycle completed in 4-6 weeks. More than one generation is completed in a crop season.
The young larvae congregate in small groups and move actively and feed on leaf lamina making small punctures. The grown-up larvae feed voraciously on the entire leaves, leaving only the main veins. The caterpillars also eat the tender shoots, buds and bolls. Sometimes, the attack is heavy and the plants may be completely defoliated.
Tarache notabilis (Walker) (Lepidoptera: Noctuidae)
Cotton semi-looper is found throughout the plains of India and Pakistan as a minor pest of cotton, but in certain years, it assumes a serious form. The full-grown caterpillars are about 40 mm long and dark green, having six pairs of black and bright-yellow spots on the back. The adults are stoutly built, white moths, with prominent grey and brown spots on the wings, measuring 30-32 mm across. The females lay green, rounded eggs singly, on the underside of the leaves. The eggs hatch in 2-4 days and the caterpillars immediately start feeding voraciously. They are full-fed in 9-16 days and then descend to the ground, where they construct earthen cells at a depth of 3 cm for pupation. They emerge as moths in 5-14 days and are short-lived. The life cycle is completed in 16-34 days. By October- November, they complete 4-5 generations.
The parasitoids associated with larvae of this pest are Actia monticola Mall. and Exorista seviloides Bar. (Tachinidae). The caterpillars feed on cotton leaves and skeltonise them altogether. In recent years of heavy infestation, the plants may be completely denuded of leaves.
Bihar hairy caterpillar
Spilosoma obliqua Walker (Lepidoptera : Arctiidae)
The Bihar hairy caterpillar is a sporadic pest and is widely distributed in the Orient. In India, it is serious in Bihar, Uttar Pradesh, Madhya Pradesh, Punjab and Haryana. It prefers to feed on a number of pulse crops, oilseeds, some vegetables and cotton.
The pest breeds from March to April and again from July to November. It passes the hottest part of the summer (May-June) and peak winter (December-February) in the pupal stage amidst plant debris. Adults emerge from over wintering pupae in March. The female lays 400- >1200 light green spherical eggs in clusters on the underside of leaves. The eggs hatch in 8-13 days and the tiny caterpillars feed gregariously for the first few days. Afterwards they disperse widely in search of food. The larva passes through seven instars in 4-8 weeks. The full grown caterpillar measures 40-45 mm in length and is profusely covered with long grayish hairs. It spins a silken cocoon in which pupation takes place in the plant debris. The pupal stage lasts for 1-2 weeks in the active period and the moths live for about a week. The life cycle is completed in 6-12 weeks and the pest passes through 3 or 4 generations in a year. The caterpillars feed on the leaves and soft portion of stem. In severe infestation, the plants may be completely denuded of leaves.
Bucculatrix loxoptera (Lepidoptera : Lyonetiidae)
Young larvae of leaf perforator hatch from minute brownish eggs in about four days and mine into the leaves. In case of severe attack, leaves are skeletonized.
Serpentine leaf miner
Liriomyza trifolii (Burgess) (Diptera : Agromyzidae)
Larvae of the serpentine leaf miner tunnel into the leaves and form mines. In case of severe attack at the seedling stage, the plants may be killed.
Bollworms are the most damaging pests of all fruiting bodies including squares, buds, flowers and bolls. Severe bollworm attack, if not properly managed, may mean complete failure of the cotton crop as all fruiting bodies may be destroyed. The bollworms include a number of species as given below.
Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechidae)
Pink bollworm is one of the most destructive pests of cotton in the Punjab, Haryana and in Pakistan. The damage is caused by the caterpillars only. They are pink and are found inside flower buds, panicles and the bolls of cotton or the fruits of okra and other allied plants. The adult is a deep brown moth, measuring 8-9 mm across the spread wings. There are blackish spots on the fore wings, and margins of the hind wings are deeply fringed.
The life cycle begins with the emergence of moths in summer. The females lay whitish, flat eggs singly on the underside of the young leaves, new shoots, flower buds and the young green bolls. The eggs hatch in about a one week and the caterpillars on emergence, are white. They turn pink, as they grow older. Soon after emergence, the larvae enter the flower buds, the flowers or the bolls. The holes of entry close down, but the larvae continue feeding inside the seed kernels. They become full-grown (8-10 mm) in about two weeks and come out of the holes for pupation on the ground, among fallen leaves, debris, etc. Within one week, the moths emerge to start the life cycle all over again. By October-November, 4-6 generations are completed.
Full-grown larvae of the last generation do not pupate. Just a few of them reach the ground, but the great majority continue feeding inside the bolls. They cut window holes in the two adjoining seeds and join them together, forming what are known as the 'double seeds'. Such damaged bolls are generally left unpicked in the field. Later, they fall to the ground and form a major source of infestation for the next year. Some are picked along with healthy cotton and reach the ginning factories, from where just a few return to the fields along with the seed. The hibernating larvae lie curled in double seed for many months and after passing the winter, they emerge as moths. The last life-cycle is very long covering 5-10 months, although during the active season, the life cycle is short, taking only 3-4 weeks.
Damage is caused in various ways. There is excessive shedding of the attacked fruiting bodies. The attacked young bolls fall off prematurely and the older ones which do mature do not contain good lint. The damaged seed-cotton gives a lower ginning percentage, lower oil extraction and inferior spinning quality.
Trichogramma achaeae Nagaraja & Nagarkatti (Trichogrammatidae) parasitizes the eggs of this pest. The parasitoid appears late in the season and is common in area where pesticides are used sparingly. The other hymenopterous parasitoids associated with larvae of the pink bollworm are Bracon greeni Ashmead and Chelonus pectinophorae Cushman (Braconidae), Elasmus johnstoni Ferriere (Elasmidae), Goniozus sp. (Bethylidae), Rogas aligharensi Quardi and Bracon lefroyi D. (Braconidae). The anthocorid bug, Triphles tantilus Motsch. (Anthocoridae) also feeds on eggs and first instar larvae.
Earias insulana (Boisduval) and E. vitella (Fabricius) (Lepidoptera: Noctuidae)
These two species of bollworms cause heavy damage to American cotton and are also found on okra and some other malvaceous plants. In the larval stage, they bore into the growing shoots, the flower buds, flowers and fruits of cotton and okra, either killing the growing points of the plants or causing heavy shedding of the fruiting bodies. In the attacked bolls, the lint is spoiled by larval feeding. The full-grown dull-green caterpillars are 20 mm long having tiny stout bristles and a series of longitudinal black spots on the body. The moths are yellow green and measure about 25 mm across the wings. E. vitella moths are of same size and have a narrow light longitudinal green band in the middle of the fore wing.
The moths appear in April and lay 200-400 eggs per female at night, singly on flower buds, brackets and tender leaves of okra and cotton plants. The hairy parts of the plants are preferred for oviposition. The eggs hatch in 3-4 days and the caterpillars pass through 6 stages, becoming full-grown in 10-16 days. They pupate either on the plants or on the ground among fallen leaves and the moths emerge in 4-9 days. The life cycle is completed in 17-29 days. In winter, the pupal stage is greatly prolonged, taking 6-12 weeks. Several overlapping generations are completed in a year. The roots of cotton plants sprouting in early spring and the fruits of neglected okra left in the field are the two important sources of early infestation and multiplication of this pest.
Trichigramma sp. parasitizes the eggs of spotted bollworms. When cotton plants are young, the larvae bore into the terminal portions of the shoots, which wither away and dry up. Later on, they cause shedding of the fruiting bodies. The infested bolls open prematurely and produce poor lint, resulting in lower market value.
Helicoverpa armigera (Hübner) (Lepidoptera : Noctuidae)
African bollworm which is traditionally a pest of chickpea and other pulse crops now regularly attacks American cotton crop in the North Zone. The moth is stoutly built and is yellowish brown. There is a dark speck and a dark area near the outer margin of each fore wing. The fore wings are marked with grayish wavy lines and black spots of varying size on the upper side and a black kidney shaped mark and a round spot on the underside. The hind wings are whitish and lighter in color with a broad blackish band along the outer margin.
The female lays eggs singly on upper aside of tender foliage of the plants. A single female may lay as many as 741 eggs in 4 days. The eggs are shiny greenish yellow and are round. They hatch in 2-4 days and the young larvae feed on the foliage for some time and later bore into the buds, flowers and bolls. They move from boll to boll and are full fed in 13-19 days and measure 35 mm in the last instar. The full grown larvae come out of the bolls and pupate in the soil. The pupa is dark brown and has a sharp spine at the posterior end. In the active season, the pupal period lasts 8-15 days. There may be as many as 8 generations in a year.
The larvae attack fruiting bodies and cause severe shedding. Unlike spotted bollworms, clean circular holes bored into fruiting bodies are free from excretory pellets/ frass. Even large sized bolls are eaten up by the grown up larvae. The larvae have a habit of moving from boll to boll and damage much more than what they actually consume.
A Nucleopolyhedrovirus (NPV) causes significant mortality among the infected larvae depending on environmental conditions.
Cotton stem weevil
Pempherulus affinis (Faust) (Coleoptera : Curculionidae)
The grubs of the cotton stem weevil feed on cotton in India and other countries of South-Asian region. In India, it occurs in Tamil Nadu, Andhra Pradesh, Karnataka, Kerala, Bihar, Orrisa, Rajasthan, Uttar Pradesh, Gujrat and Assam. The adult is dirty brown or greyish black weevil, about 3 cm in length. The grub is slightly curved, creamy white, with a distinct head. During an oviposition period of 60-80 days, a female may lay upto 121 eggs visiting from plant to plant. The eggs hatch in 6-10 days and the grubs feed inside the soft stem tissue. They continue to feed inside till the development is completed in 35-57 days. The pupation takes place inside the stem and this stage lasts from 25 to 30 days. Three generations are completed in a year from October to April. These beetles infest the young crop. As the grubs tunnel within the stem, that portion swells forming galls and such symptoms are generally seen at the base of the plant. The younger plant when attacked succumbs, while the older plants may survive but suffer in vigour. Under strong winds and heavy boll load even elder plant may break at the swellings. The pest causes plant mortality upto 25 per cent, especially during the early stages of growth.
Alcidodes affaber Aurivillus (Coleoptera : Curculionidae)
Internode borer is a serious pest in South India. The weevils lay eggs at the node axle and the grubs feed on the tissue at the axle. The affected leaves wilt and droop. Severe damage on several leaf axles leave the plant wilted affecting seed cotton yield. The younger plants are especially susceptible to this borer. These weevils also damage the plants by stem girdling and boring which leave the characteristic ring of frayed fibers. The upper part of plant dies and often breaks off at the girdle.
Red Cotton Bug
Dysdercus koenigii (Fabricius) (Hemiptera: Pyrrhocoridae)
Red cotton bug is a minor pest of cotton in the North Zone. The bugs are elongated slender insects, crimson red with white bands across the abdomen. The membranous portion of their fore wings, antennae and scutellum is black. Both adults and nymphs feed on the cell sap of cotton, hollyhock, wheat, maize, pearl-millet, clovers, etc.
This insect is active throughout the year and passes winter in the adult stage. In spring, the bug becomes active and lays, on an average, 100-130 eggs in moist soil, in crevices in loose irregular masses of 70-80 eggs each. The slender nymphs later develop black markings on the body. There are 5 nymphal stages and the development is completed in 49-89 days. In summer, the life of an adult is very variable, but in winter, it may live up to three months.
The pest is generally serious at the boll bursting stage. Heavily attacked bolls open badly and the lint is of poor quality. The bugs stain the lint with their excreta or body juices as they are crushed in the ginning factories. The staining of lint by the growth of certain bacteria inside the bolls is also believed to be initiated by these bugs.
Dusky Cotton bug
Oxycarenus laetus Kirby (Hemiptera: Lygaeidae)
This is minor pest of cotton and its chief importance lies in the fact that the adults nymphs get crushed at the time of ginning, thus staining the lint and lowering the market value of cotton. The adults are 4-5 mm in length, dark brown and have dirty white transparent wings. The young nymphs have a round abdomen and, as they grow older, they resemble the adults except for being smaller and having prominent wing pads instead of wings.
The cigar-shaped eggs are laid on cotton during the monsoon. Initially, they are whitish turning pale and finally becoming light pink before hatching. The eggs are usually laid in the lint of half opened bolls, either singly or in small clusters of 3-18 each. The egg stage lasts 5-10 days and the nymphs, on emerging, pass through 7 stages, completing the development in 31-40 days. The life cycle lasts 36-50 days and a number of generations are completed in a year.
Agrotis ipsilon (Hufnagel) (Lepidoptera : Noctuidae)
Greasy cutworm is a pest of world wide occurrence and is recorded in Asia, Australia, Africa, America and Europe. In India, it is reported from northern and central regions. This phytophagous pest prefers feeding on potato, chickpea, tobacco, wheat, maize, mustard, linseed, sugarcane, cotton and several other crops. The pest is active from October to April and probably migrates to the hilly regions for summer breeding. The eggs are laid in clusters on the undersurface of leaves in October. The larval period lasts for more than a month. When full grown, the larva make earthen chambers in the soil and pupate underground. The moths usually emerge at night. The life cycle is completed in 48-77 days and generally three generations are completed in a year. The caterpillars damage the germinating cotton crop by cutting their stems near the ground surface usually at night.
Microtermes obesi Holmgren and Odontotermes obesus (Rambur) (Isoptera : Termitidae)
Both M. obesi and O. obesus are important pests of several economically important crops like wheat, sugarcane, cotton, barley and groundnut. These termites live in large colonies and feed on the roots of cotton plants penetrating the roots then tunnelling up into the stem replacing the tissue with soil. In young plants the first sign of attack is wilting during the day followed shortly by death. If the plant is dug up, tunnels in the roots or stems are evident usually containing termites. The well developed root system of older plants may help them survive the attack.
Insecticide Use on Cotton in India
In view of its great importance as a cash crop and its susceptibility to insect pests, cotton receives a disproportionately large share of pesticides. At the global level, roughly one fourth of the total pesticides used all over the world are applied to protect the cotton crop, while in India the share of the pesticide on this crop which occupies around 5 per cent of the cultivated area, is around 40 per cent of the national agricultural consumption of pesticides. Despite heavy use of pesticides, losses caused by insect pests continue to be unacceptably high. In India, the insect pests reduce cotton crop production by around 50 per cent (Dhaliwal and Arora, 2001).
Development and Adoption of IPM Technology in Cotton
In India, cotton was the first crop for which IPM technology was developed. The Indian Council of Agricultural Research, New Delhi, sponsored a village level project to evaluate and demonstrate the efficacy, practicability and economics of IPM in cotton in the Punjab in 1975. The main components of IPM technology at that time are as given below (Simwat, 1994).
Adoption of short duration jassid-tolerant varieties of American cotton
Judicious use of irrigation and fertilizers
Cultural and mechanical control measures for minimizing the carryover and build up of pink bollworm
Removal of alternate host plants of spotted bollworms in and around the cotton fields
Economic threshold based sprays for the control of cotton jassid
Effective boll formation period was determined for different varieties and calendar based sprays were recommended during this period for management of bollworms
The adoption of IPM technology over a 15 year period resulted in 73.7 and 12.4 per cent reduction in the number of insecticide sprays for the control of sucking pests and bollworms, respectively. Properly timed sprays along with a number of cultural and mechanical practices resulted in a 38.5 per cent reduction in bollworm incidence in operational research project (ORP) area as compared to the adjoining non ORP area. Despite reduced plant protection expenditure, the ORP farmers obtained 23.2 per cent higher yield and 31.7 per cent higher net income that non –ORP farmers (Sidhu et al., 1990, Dhaliwal and Arora, 2001). Similar programmes were also adopted in other cotton growing areas of the country.
Recent Studies on Cotton IPM in Punjab
The main cotton research center in Punjab is located at PAU Regional Station, Faridkot. An IPM trial was conducted for the management of cotton pests at RS, Fraidkot for the 4 years from 2002 to 2005. The IPM practices were compared with the general spray schedule (GSS) in which calendar based sprays were applied for the control of bollworms. An untreated control (check) was also kept during 2002 season. The trial was conducted on a single variety F 1378 during the 2002 season, while during 2003 and 2004 seasons, two varieties F 1378 and F 1861 were included in the trial. In season 2005 the trial was conducted on F 1861 and Bt cotton hybrid RCH 134. Both F 1378 and F 1861 are American cotton varieties developed at RS, Faridkot and Bt RCH 134 is developed by RASSI Pvt Ltd. These varieties and the hybrid transgenic are recommended for cultivation in the Punjab by Punjab Agricultural University, Ludhiana (PAU, 2005). Both the varieties are moderately resistant to the jassid and in addition F 1861 is also resistant to cotton leaf curl virus. Bt RCH 134 is resistant to bollworms.
Some of the IPM practices were adopted on an areawide basis. These mainly included the cultural and mechanical control measures for minimizing the carryover of pink bollworm.
Sheep and goats were allowed to feed on unpicked bolls and burs left in the cotton fields after the last picking.
Cotton sticks were removed from the cotton fields after the crop season. Cotton sticks are used as fuel wood by the farmers and unpicked bolls on these sticks are the main source for carryover of the pink bollworm.
The cotton seed kept for sowing for the next season was fumigated to kill the diapausing larvae of the pink bollworm.
The benefit of reduced carryover due to adoption of these practices was the same for the both IPM and the GSS treatments. In addition recommended variety was grown in both the treatments. The PAU recommended crop cultivation, irrigation and fertilizer application practices were adopted uniformly in the experimental area (PAU, 2005).
Other IPM practices were adopted only in IPM plots. These included:
Removal of weeds acting as alternate hosts of insect pests.
Seed treatment with imidacloprid @5 g / kg seed for jassid control.
Two border rows of pearlmillet for attracting predatory birds which feed on bollworms.
Mechanical removal of spotted bollworm infested twigs.
Economic threshold based sprays for jassid control when nearly 50 per cent of the total plants show yellowing and curling on the margins of leaves in the upper canopy (II garde injury level).
Economic threshold based sprays for bollworms control when 5 per cent of shed fruiting bodies appear to be damaged by bollworms.
In the GSS plot, the jassid sprays were based on ETL, while the bollworm sprays were conducted at 10-days intervals during the effective boll formation period. The data were recorded on the incidence of sucking pests, bollworms and seed cotton yield in each plot.
The results on incidence of sucking pests and bollworms, number of sprays and seed cotton yield in IPM Vs GSS are presented in Tables 1, 2, 3 and 4 for the year 2002, 03, 04 and 2005, respectively. The mean number of sprays were 7.0, 7.7 and 4.0 in GSS as compared to 4.3, 4.7 and 3.0 in IPM in the cotton varieties F 1378, F 1861 and Bt RCH 134, respectively. Overall, the IPM plots required 35.69 per cent less sprays as compared to GSS plots across the varieties. But the bollworm incidence and seed cotton yield did not differ significantly between the IPM and the GSS plots. The overall bollworm incidence on percent boll basis was 16.68 and 15.42 per cent in IPM and GSS plots, respectively. The corresponding values for percent loculi attacked were 9.73 and 9.06, respectively. But in seed cotton yield, the IPM plots out yielded the GSS plots by 6.5 per cent in F 1378, 0.27 per cent in F 1861 and 0.59 per cent in Bt RCH 134. The overall yield advantage in IPM plots across varieties was 1.25 per cent.
Results of our trials point to the necessity of widening the range of IPM practices adoption and also persuading the farmers to adopt economic threshold based sprays for bollworm management in cotton. This will reduce the pesticide load in the ecosystem further by nearly one third and lower the cost of cultivation significantly without adversely affecting the yield of the crop.
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