Learn about the pests that damage cotton and its control.
1. Cotton Jassid, Amrasca Biguttula Biguttula (Ishida) (Hemiptera: Cicadellidae):
The cotton jassid is widely distributed in India and is the most destructive pest of American cotton in the north-western regions. Besides cotton, are also feeds on okra, potato, brinjal and some wild plants, like hollyhock, kangi buti (Abutilon indicus), etc. Damage to the crop is caused by the adults as well as by the nymphs, both of which are very agile and move briskly, forward and sideways. 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 disturbances and are also attracted to light at night.
Life-Cycle:
The pest breeds practically throughout the year, but during the winter months, only adults are found on plants such as potato, brinjal, tomato, etc. In spring, they migrate to okra and start breeding. The females lay about 15 yellowish eggs on the underside of the leaves, embedding them into the leaf veins.
The eggs hatch in 4-11 days and give rise to nymphs which are wedge-shaped and are very active. They suck cell-sap from the underside of the leaves and pass through six stages of growth in 7-21 days. On transformation into winged adults, they live for 5-7 weeks, feeding constantly on the plant juice. The pest completes seven generations in a year.
Chrysoperla sp. (Chrysopidae) and spiders like Distina albida L. feed on nymphs and adults. No other parasitoids are known for this insect.
Damage:
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, causing up to 35 per cent reduction in yield.
Control:
(i) At the time of sowing, smear the cotton seed with imidacloprid 70WS @ 5g/ kg seed or thiomethoxam 70WS @ 3 g/kg seed.
(ii) Spray against jassid should be done at economic threshold level of 1-2 nymphs per leaf or when second grade injury symptoms (yellowing and curling at margins of leaves) appear in 50 per cent of the plants. Any one of the following insecticides can be used in 250 litres of water per ha: 100 ml of imidacloprid 200 SL, 100 ml of imidacloprid 555, 100 ml of imidacloprid 17.8SL, 50 g of acetamiprid 20SP, 100g thiomethoxam 25WG, 200 g flonicamid 50WG.
2. Cotton Aphid, Aphis Gossypii Glover (Hemiptera: Aphididae):
The insect is distributed throughout India and is considered as a potential pest of cotton. It also infests many other crops like okra, brinjal, guava, gingelly, etc. The adults are small, soft and greenish-brown insects found in colonies on the tender parts of the plants. The adults exist both in winged and wingless forms.
Life-Cycle:
The alate as well as apterous females multiply parthenogenetically and viviparously. The female may give birth to 8-22 nymphs in a day. The nymphs moult four times to become adults completing the life-cycle in 7-10 days. The aphids also lay eggs which overwinter.
The coccinellid beetles, Coccinella septempunctata Linnaeus and Menochilus sexmaculatus (Fabricius) are the common predators feeding on this insect. The aphids are also parasitized by Aphelinus mali (Haldeman) and A. abdominalis (Dolman).
Damage:
The aphids live in colonies on the tender portions of the plants and suck the sap. In case of severe infestation, the plants become weak; leaves curl up and wither. There is stunted growth, gradual drying and death of the plants. The younger plants are more susceptible than the older ones. The honey-dew secreted by the aphid encourages sooty mould growth on the leaves. The dry conditions favour rapid increase in pest population.
Control:
Spray 750 ml of oxydemeton methyl 25EC or 625 ml of dimethoate 30EC in 250 litres of water/ha, when honeydew appears on 50 per cent plants.
3. Cotton Whitefly, Bemisia Tabaci (Gennadius) (Hemiptera: Aleyrodidae):
This pest is distributed throughout the northern and western regions of the Indian Subcontinent and is a very serious pest of American cotton, particularly in the dry areas. Apart from cotton, this insect also feeds on various other plants such as cabbage, cauliflower, sarson, toria (Brassica campestris), melon, potato, brinjal, okra and some weeds.
The louse-like nymphs, which suck the 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 have prominent long hind wings.
Life-Cycle:
The insect breeds throughout the year and all the developmental stages are noticed, although adults predominate in the cold season. The females lay eggs singly on the underside of the leaves, averaging 119 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, 5-17 days in October- November and 33 days in December-January.
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, and in 17-81 days in October- March. In 2-8 days, the pupae change into white flies. The life-cycle is completed in 14-122 days and 11 generations are completed in a year.
Eretmocerus massii Silv. (Aphelinidae) is associated with nymphs and pupae, and incidence of parasitization reaches up to 33 per cent while Encarsia 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.
Damage:
Damage by this pest is caused in two ways:
(a) The vitality of the plant is lowered through the loss of cell sap
(b) Normal photosynthesis is interfered with due to the growth of a sooty mould on the honeydew excreted by the insect.
From a distance, the attacked crop gives a sickly, black appearance. Consequently, the growth of the plants is adversely affected and when the attack appears late in the season, the yield is lowered considerably. B.tabaci is known to transmit a number of virus diseases including the leaf curl disease of tobacco, the vein clearing disease of okra and the leaf-curl of sesame.
Control:
Chemical control measures are same as in case of cotton aphid. In addition, spray 500 g of diafenthiuron 50WP or 500 ml of spiromesifen 240SC or 1.5 litres of triazophos 40EC or 2.0 litres of ethion 50EC during boll formation phase. The economic threshold level is 20 nymphs or 8-10 adults/leaf or leaf stickiness due to deposition of honeydew by insects in 50 per cent of plants.
4. Dusky Cotton Bug, Oxycarenus Laetus Kirby (Hemiptera: Lygaeidae):
This is a minor pest of cotton in India and its chief importance lies in the fact that the adults and nymphs get crushed at the time of ginning, thus staining the lint and lowering the market value of cotton. Besides cotton, it also feeds on okra, hollyhock and other malvaceous weeds.
The adults are 4-5 mm in length, dark brown and have dirty white transparent wings. The young nymphs have a rotund abdomen and, as they grow older, they resemble the adults, except for being smaller and having prominent wing pads instead of wings.
Life-Cycle:
The insect is active practically throughout the year, but during winter, only adults are found in the unginned cotton. The cigar-shaped eggs are laid in the spring on Hibiscus and then on okra and finally 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.
Triphleps tantilus Motsch (Anthocoridae) feeds on the nymphs of this bug and no other parasitoids are known.
Damage:
The nymphs and adults suck the sap from immature seeds, whereupon these seeds may not ripen, may lose colour and may remain light in weight. The adults found in the cotton are crushed in the ginning factories, thus staining the lint and lowering its market value.
5. Red Cotton Bug, Dysdercus Koenigii (Fabricius) (Hemiptera: Pyrrhocoridae):
This insect is widely distributed in India and is a minor pest of cotton in the Punjab and Uttar Pradesh. Apart from cotton, it also feeds on okra, maize, pearl millet, etc. 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.
Life-Cycle:
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 or in crevices in the ground. The eggs are spherical, bright yellow and are laid in clusters or in loose irregular masses of 70-80 eggs each.
They hatch in 7-8 days and the young nymphs have flabby abdomens, but as they grow older, they become more slender and 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 predacious bugs like Antilochus cocqueberti Fabricius (Pyrrhocoridae) and Harpactor costalis (Stal) (Reduviidae) feed on nymphs and adults.
Damage:
The insects suck cell-sap from leaves and green bolls of cotton. Heavily attacked bolls open badly and the lint is of poorer quality. The seed produced may also have low germination and less oil. Moreover, 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.
6. Cotton Mealybug, Phenacoccus Solenopsis Tinsley (Hemiptera: Pseudococcidae):
Cotton mealybug has recently emerged as a serious pest of cotton in several Asian countries including India and Pakistan. Besides cotton, it also feeds on tomato, mustard, sorghum and bakain (Melia azedarach) trees, and several weed plants like congress grass (Parthenium hysteropliorus), kanglii buti (Abutilon theophrasti), peeli buti (Abutilon indicum), puthkanda (Achyranthes aspera), gutputna (Xanthium strumarium), bhakhra (Tribulus terrestris), itsit (Trianthema portulacastrum) and tandla (Digera arvensis).
This insect severely infected the cotton crop in the cotton growing provinces (Sindh and Punjab) of Pakistan in 2005 and 2006. In India mealybug appeared in serious proportions in 2006 in cotton growing areas of Punjab, Haryana, Rajasthan, Maharashtra and Gujarat, and caused widespread damage to cotton. It struck in epidemic form in 2007 and at many places; farmers had to plough down their badly infested crop.
The adult is pink and elongated oval (about 3 mm in length), flattened and covered with a white mealy powder. The female adults are wingless; however, male adults are having one pair of wings. The nymphs are pale yellow with reddish eyes, which are later on covered with white powdery mass.
Life-Cycle:
A female lays 150-600 eggs usually in cotton like ovisac beneath her body. The embryonic development of the young ones takes place within the body of the female (ovoviviparity). The eggs hatch in 6-9 days. The newly emerged nymphs (crawlers) crawl out and start feeding on young plants.
They prefer the growing shoot of the plant which is soft and juicy. Tater on, they attack the older lower portion of the cotton plant. Its population increases tremendously and soon a colony is formed. Mature females are relatively sessile with a large, out-pocketing cottony pouch from the posterior end, stuffed with its offspring.
In case of severe infestation, the mealybug occurs in the form of clusters with white cottony crawler sacs protruding from the anal region of their body. Thus, unspecified protective layers are formed due to the overlapping and clinging of one mealybug over another. The female mealybugs pass through four instars in 10-15 days. The longevity of the adult is 7-14 days. The total life-cycle is completed in 25-30 days and there may by 14-15 generations in a year.
Damage:
The mealy-bug first attacks the alternate hosts growing in outer region of the cotton fields and then shifts to the cotton crop. Both nymphs and adults suck the sap from leaves, flower buds, petioles, twigs, internodes and even from the stem of the cotton plants.
The insect heavily sucks the sap from the plant and renders it weak, feeble and dehydrated. In severe cases, defoliation takes place by the development of sooty mould on honeydew produced by crawlers. The sooty mould reduces the photosynthetic ability of the plants. In addition, mealybug also injects toxins into the host tissues.
The flower buds, flowers, immature bolls and even the leaves fall down, and the growth of the plant are retarded. The infested plants bear fewer bolls of smaller size and there is incomplete opening of bolls. The entire plant remains stunted and shoot tips develop a bushy appearance. The cotton plant exhibits a die-back of growing shoots and twigs, ultimately reducing the yield.
This damage of the pest is initiated from the borders and spreads to the main cotton crop. White cottony heads appear on the infested plants where intensive infestation of all the stages can be observed. Its infestation starts in patches and in case of severe infestation, the infested plants give the appearance of a field sprayed with a defoliant or herbicide.
Control:
Management of mealy-bug is difficult due to its wide host range, wax coating on the body, dense colonies, nature of hiding in cracks and crevices in the bark, crawling off the host plants and easy spread to other areas.
However, the following IPM strategy helps to keep the pest under check:
(i) To check the spread of mealybug, remove regularly the weeds growing adjacent to road sides, pathways, water channels and waste lands,
(ii) Destroy the infested host plants along with the pest very carefully, preferably by burning/deep ploughing, but never throw in open water channels,
(iii) Avoid growing cotton near the fields of tomato, sorghum and bakain trees, as they serve as alternate hosts of mealybug,
(iv) Grubs of green lace wing, Chrysoperla carnea (Stephens) and adults of Cryptolaemus montrouzieri Mulsant could be used as biological control agents as they feed on the nymphs of the mealy-bug.
(v) In case of severe infestation, spray any one of the following insecticides in 300-400 litres of water per ha-
(a) Carbamates. 2.5 kg of carbaryl 50WP or 625 g of thiodicarb 75WP.
(b) Organophosphates. 1.25 litres of profenophos 50EC or 2.0 litres of quinalphos 25EC or 2.0 kg of acephate 75SP or 5.0 litres of chlorpyriphos 20EC.
(c) Insect growth regulator. 1.25 litres of buprofezin 25EC.
(d) The first spray should preferably be done with carbamates and if required, repeat spray after 5-7 days with organophosphates.
(e) Since damage of mealybug is normally localised to border rows, treat only these rows with the above pesticides.
7. Pink BoIIworm, Pectinophora Gossypiella (Saunders) (Lepidoptera: Gelechiidae):
The pink bollworm is one of the most destructive pests of cotton in the world and is found in America, Africa, Australia and Asia. It is highly destructive in the Punjab, Haryana and 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. In the adult stage, the insect is a deep brown moth, measuring 8-9 mm across the spread wings. There are blackish spots on the fore wings, and the margins of the hind wings are deeply fringed.
Life-Cycle:
The yearly life-cycle begins with the emergence of moths in the summer. The emergence takes place at two distinct times- in May-June, and then in July-August. 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 one week and the caterpillars, on emergence, are white and 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, however, pupate. Just a few of them reach the ground, but the great majority keeps 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 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 seeds 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. The pest passes through several broods during its active period.
Trichogramma achaeae Nagaraja & Nagarkatti (Trichogrammatidae) parasitizes the eggs of this pest throughout India and the incidence is 6-27 per cent in North India. It appears late in the season and is common in area where pesticides are used sparingly.
Releases of Trichogramma spp. at 1,50,000 parasitized eggs ha-1 at weekly intervals have proved promising for bollworm control. Apanteles angaleti Muesebeck (Braconidae) parasitizes 1-17 per cent of the larvae of the host. It is widely distributed in India and the parasitoid is associated with the host throughout the year.
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 Quadri and Bracon lefroyi D. (Braconidae). An eulophia parasitizes the pupae of this pest. The anthocorid bug, Triphles tantilus Motsch. (Anthocoridae) also feeds on eggs and first instar larvae.
Damage:
Damage is caused in various ways. When flower is infested, a typical rosette-shaped bloom harbours the larvae. There is excessive shedding of the fruiting bodies. Of the total shedding, 52.4-88.8 per cent is caused by all the bollworms collectively; one half may be due to the attack of pink bollworm.
The attacked bolls fall off prematurely and those which do mature do not contain good lint. The damaged seed-cotton gives a lower ginning percentage, lower oil extraction and inferior spinning quality. It is considered that by controlling the pink and spotted bollworms, the cotton yield can be increased upto 50 per cent.
Control:
(i) The destruction of off-season cotton sprouts, alternative host plants or the burning of plant debris from cotton fields, minimizes the incidence of this pest,
(ii) Deep ploughing with a furrow-turning plough by the end of February is also helpful in reducing the carry over of this pest to the next season.
(iii) Release of Trichogramma chilonis Ishii @ 1,50,000/ha starting from 70th day after sowing at weekly interval with a total of 8-10 releases is effective against bollworm.
(iv) In case the bollworm damage exceeds 5 per cent, the crop should be sprayed immediately and thereafter at 10-day interval with any of the following insecticides in 315-375 litres of water per ha-
(a) Organophosphates. 2.0 litres quinalphos 25EC, 1.25 litres monocrotophos 36SL, 5.0 litres chlorpyriphos 20EC, 1.5 litres triazophos 40EC, 2.0 litres ethion 50EC, 2.0 kg acephate 75SP, 1.25 litres of profenophos 50EC.
(b) Carbamates. 2.5 kg carbaryl 50WP, 625 g thiodicarb 75WP.
(c) Synthetic pyrethroids. 500 ml cypermethrin 10EC, 200 ml cypermethrin 25EC, 400 ml deltamethrin 2.8EC, 250 ml fenvalerate 20EC, 250 ml alphamethrin 10EC, 750 ml β-cyfluthrin 0.25SC, 750 ml fenpropathrin 10EC.
(d) Miscellaneous. 150 ml spinosad 48SC, 100 ml flubendiamide 48SC, 500 ml indoxacarb 15SC, 625 g thiodicarb 75WP, 375 ml novaluron 10EC.
(v) At least 5-6 sprays are required for effective control of bollworms. Same insecticide should not be sprayed repeatedly to avoid the development of pesticide resistance and appearance of secondary pests. Also, avoid using insecticides of the same group in more than three sprays.
8. Spotted Bollworms, Earias Insulana (Boisduval) and E. vittella (Fabricius) (Lepidoptera: Noctuidae):
These two species of bollworms are widely distributed in North Africa, India, Pakistan and other countries, and are serious pests of cotton. In Punjab, they cause heavy damage to American cotton and are also found on okra (Abelmoschus esculentus L.), sonchal (Malva parviflora), gulkhaira (Althaea officinalis), hollyhock (Althaea rosea) 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 plants or causing heavy shedding of the fruiting bodies. In the attacked bolls, the lint is spoiled by larval feeding. Okra fruits become distorted and are rendered unfit for human consumption.
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. vittella moths are of the same size and have a narrow light longitudinal green band in the middle of the fore wing.
Life-Cycle:
The pests breed practically throughout the year but during the winter only the pupae are found hiding in plant debris. The moths that appear in April live for 8-22 days and lay 200-400 eggs at night, singly on flower buds, brackets and tender leaves of okra or cotton plants. The hairy parts of the plants are preferred for oviposition.
In warm weather, 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 during the summer.
In winter, the eggs hatch in about one week and 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.
Trichogramma chilonis Ishii (Trichogrammatidae), an egg parasite is widely distributed in India and Pakistan. In North India, the incidence varies from 3 to 15 per cent. The release of parasitoids in cotton fields is very useful in reducing the incidence of pest.
Trichogramma brasiliensis (Ashmead) (Trichogramma-tidae), the exotic parasitoid, has been tried in the Punjab and other cotton growing areas. The releases of this parasitoid reduced the incidence by 50 per cent in experimental fields. The unilative releases in July-August and inoculative releases afterwards are recommended.
Another egg parasitoid, Trichogrammatoidea sp. near guamensis (Trichogrammatidae) is also associated with this pest. Brachymeria nephantidis Gahan (Chalcididae) has also been recorded from pupae of Earias sp. and parasitism ranges from 13 to 57 per cent in different months. The parasitoids associated with larvae of P. gossypiella are also associated with this pest.
Damage:
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 30-40 per cent shedding of the fruiting bodies. The infested bolls open prematurely and produce poor lint, resulting in lower market value.
Control:
(i) The pest can be suppressed with clean cultivation and the destruction of alternative food plants, particularly when cotton or okra is not growing in that locality,
(ii) Chemical control measures are same as in case of pink bollworm. The economic threshold level is 10 per cent incidence in shoots or reproductive parts.
9. American Bollworm, Helicoverpa Armigera (Hubner) (Lepidoptera: Noctuidae):
The American bollworm has become a serious pest of cotton in northern parts of India. It was first reported on cotton in 1977 in Punjab. In 1983, it appeared in serious form in the northern cotton growing belt and reduced yield by 40-50 per cent. Again in 1990, it caused severe losses to cotton in Haryana, Punjab and Rajasthan.
The incidence of this pest has decreased after the introduction of Bt cotton The insecticides effective against pink bollworm are also effective against this pest. The economic threshold is 10 per-cent incidences in reproductive parts.
Control:
(i) Avoid the cultivation of okra, moong, arhar, dhaincha and castor in and around cotton crop,
(ii) Avoid growing American cotton in orchards.
(iii) Chemical control measures are same as in case of pink bollworm. Prefer to use acephate/chlorpyriphos against grown up larvae (more than 1.25 cm long) of American bollworm. Spinosad and indoxocarb should be used only in emergency at higher incidence of pest when it becomes difficult to control with other insecticides.
10. Cotton Leaf Roller, 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 tracts and is an important sporadic pest. Besides cotton, it has also been recorded on various other malvaceous plants like okra, gulkhaira (Althaea officinalis), kanghi buti (Abutilon indicum) and some forest trees.
Damage is done by caterpillars, which measure about 25-30 mm in length when full- grown. They are greenish grey or pink and 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 dark brown wavy lines on the wings.
Life-Cycle:
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, then they mate and lay 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 leaf 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. They emerge as moths 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.
From March to June, the infestation develops mostly in thick plantations of forest trees but during the monsoon, it spreads to nearby fields of American cotton. The low maximum temperature, high relative humidity and cloudy weather are considered to be favourable for the rapid multiplication and spread of this pest.
Trichogramma spp. (Trichogrammatidae) attack the eggs while Brachymeria tachardiae Cam. (Chalcididae), Elasmus indicus Rohn. (Elasmidae), Goryhus nursei Cam. (Ichneumonidae) and Trichospilus pupivora Ferrieri (Eulophidae) are associated with the larvae of this pest. T. pupivora was also introduced in Pakistan from India and releases were made but it failed to establish there.
Damage:
The larvae feed on cotton leaves and in years of serious outbreaks, the cotton plants may be completely defoliated. American cotton is preferred over desi cotton by this pest.