Learn about how to control pests of cotton and fibre crops!
1. Red Cotton Bug:
Dysdercus Koenigii Fabr. (Heteroptera- Pyrrhocoridae):
It is a serious pest of cotton and sucks juice with its long beak from the seed of either green or ripe cotton bolls. Both the nymphs and adults are voracious feeders and cause extensive damage to the plant. The main symptom of attack by this pest is the shrivelling of bolls in the plant. A severe infestation by this pest causes serious impairment to the vitality of the plant and destroys the germinating power of the seed by the loss of its oil contents. Besides these features, the formation of lint is badly affected.
Although D. koenigii is a major pest of cotton, this insect has been reported to thrive well on other malvaceous plants like Hollyhock, lady’s finger (Okra) or in other non-malvaceous plants like sweet potato, tobacco etc.
Life History:
The eggs of D. koenigii when freshly laid are soft to touch, they are almost round yellowish-white in colour and a little over 1 mm. long. They are laid in loose clusters, about 80-100 per cluster normally in cracks on the surface of the moist soil or under fallen leaves round about the plants.
The eggs hatch out under favourable conditions in about 7 days. Small, active yellowish-red first instar nymphs hatch out which resemble the adults except in size and absence of wings. They are about 1.5 mm. long dorsally flattened and convex possessing 4 – jointed antennae and two jointed tarsi. The nymph generally clusters round the cotton bolls. In course of time moulting occurs and there are normally 4 moults or 5 instars before a fully developed adult individual is formed.
The average time taken for all the 4 moults is BOSS days under favourable conditions. The duration between any two successive moults is dependent on many factors one of them being food. Under unfavourable conditions, there may be 5 moults and 6 instars and the moulting period may extend to 82 days. Generally the entire life cycle of this pest is completed in about 42-45 days.
This insect normally breeds on cotton from August to November, on Hollyhock from November to March or April, and on lady’s finger (Okra) from April to July each year. Many of them hibernate in the adult stage from December to middle of March.
There are several ways of controlling this pest. Often the mechanical methods such as hand picking, trapping etc. are adopted. Chemical control chiefly advocates the employment of certain synthetic insecticides like dust 5% malathion or carbaryl as spray.
2. Dusky Cotton Bug:
Oxycarenus Laetus Kirby (Heteroptera- Lygaeidae):
It is a minor pest of cotton. The adult bugs are very small about 4 to 5 mm. in length, brown in colour. Both the young and adult sucks the sap of immature seeds of the cotton. Lint is stained when they are crushed in factories. There are several other host plants belonging to Family Malvaceae.
Each female lays white 15 to 40 eggs singly or in groups of 4 to 18 on the half open bolls which become pink later on. After about one week or more nymph emerges. There are seven instars. The total time taken for development ranges from 30 to 40 days. There are several generation in a year.
The dusky cotton bugs can be controlled by applying methyl demeton 25EC @ 1 litre/ha in 1000 litres of water in the form of spray on the crop.
3. Cotton Leaf Roller:
Sylepta Derogata Fabr. (Lepidoptera- Pyraustidae):
The cotton leaf roller occurs in all the cotton- growing tracks and is an important sporadic pest. It is distributed throughout the India. Damage is done by the caterpillars. The larvae feed on cotton leaves and in the years of serious outbreaks, cotton plants may be completely defoliated.
Life History:
The moths are active at night when 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 at first feed on the lower surface of the leaves. The damage is caused by caterpillars. The larvae grow through 7 stages and are full fed in 15-35 days. The full grown larvae measure about 25-30 mm. in length. They are greenish-grey or pink and are found feeding inside the rolled leaves.
Pupation takes place either on the plant or inside the rolled leaves or in the soil. They emerge as moths in 6-12 days and live for about a week. Moths are yellowish- white in colour with black or brown spots on the head and thorax. They measure about 28-40 mm. across the spread wings. They remain active from March to October. The life cycle is completed in 23-53 days and the pest passes through 5 or 6 generations in a year.
The pest, as in other cases, can be controlled by spraying the infested crop with carbaryl 0.1% or endosulfan 0.05% or fenitrothion 0.075%.
4. Cotton Jassid:
Empoasca Devastans Dist. (Homoptera- Cicadellidae):
The jassids are popularly known as ‘leaf hoppers’, because their legs are specially developed and modified for hopping like those of locusts and grasshoppers. All the nymphal stages as well as adults inflict the same type of damage. Like other bugs, they suck out the cell sap from the plant tissue. Adults are about 3 mm. long and greenish yellow in the summer and have a reddish tinge in the winter.
Life History:
The eggs are usually inserted into the parenchymatous tissue, between the vascular bundles and the epidermis. Each female lays about 15 yellowish eggs, which hatch in 4-11 days. The nymphs moult 5 times and the whole life cycle is completed in about 2 weeks to more than a month and half depending on the climatic conditions.
On transformation into winged adults, they live for 5-7 weeks feeding constantly on the plant juice. The pest completes 7 generations in a year but as many as 11 generations have been recorded in some parts of the country.
The jassids can be controlled by spraying the infested crop at 15 days intervals with a number of insecticides like phosphamidon 0.02%, malathion 0.05%, endosulfan 0.05% and monocrotophos 0.03%.
5. Cotton Whitefly:
Bemisia Tabaci Genn. (Homoptera- Aleurodidae):
The common name whitefly is applied to a group of small (about 1 mm. or so) sucking insects. The damage is caused by sucking the cell sap. The growth of the plants is adversely affected and when the attacks appears late in the season, the yield is lowered considerably.
Life History:
The females lay eggs singly from 70-119 eggs per female in 1-4 weeks’ time. The insect can often breed parthenogenetically i.e. without mating. The eggs are light yellow in the beginning but turn brown later on. They hatch in 3-5 days in April to September, 5-17 days in October – November and 33 days in December – January.
The elliptical nymphs feed on the cell sap and grow into 3 stages to form the pupae within 9-14 days in April – September, and 17-81 days in October- March. In 2-8 days, the pupae change into white flies. The whole life cycle is completed in 14-122 days and 11 generations are completed in one year.
The pest can be controlled by spraying the infested crop at 15 days intervals with any one of these insecticides- phosphamidon 0.02%, malathion 0.05%, endosulfan 0.05%, methyl demeton 0.025%.
6. Spotted Boll – Worm:
Earias Fabia Stoll (Lepidoptera- Noctuidae):
It is equally a serious pest of cotton and the young larvae devour the tender shoots, leaves, flower buds and ripening bolls of the plant. The lint and seeds are completely destroyed and the yield is reduced by 10 – 50%. Like D. koenigii this pest also infests other food plants like lady’s finger (Okra), Hollyhock etc.
The female lays round eggs about 2-4 hundred in number singly on bolls, terminal leaves or buds or flowers. These eggs hatch in 4 – 7 days into dark pale greenish larvae with black dots and short spine like hairs on either side of the back. As soon as they hatch, they bore into the tender shoots and later on reach the flowers and bolls. The full grown larvae having a brownish white body, spotted with different colours like brown, green, black and orange.
Hence it is called “spotted boll worm”. The larval period lasts for 9-16 days depending upon atmospheric conditions. At the end of the larval period they move out of the boll and pupate in a tough grey silken cocoon on plant or soil. The pupal period ranges from 10-12 days after which fresh moth emerges. The entire life cycle spreads over a period of 26-35 days.
Control:
While the mechanical control is occasionally employed by hand picking the caterpillars and destroying them, the most common method of control is spraying of the insecticides like endosulfan 35EC @ 1.25-1.50 litres/ha in 1000 litres of water, 0.1% carbaryl or 0.03% monocrotophos at 15 days intervals 2-3 time controls the pests. Removal of damaged parts of the plant is also useful.
7. Pink Boll – Worm:
Pectinophora Gossypiella Saund. (Lepidoptera- Gelechiidae):
This is another serious pest of cotton, and the caterpillar 8-10 mm in length, damages the bolls vehemently, consequently the seeds inside the bolls are completely devoured and the formation of lint is affected. In fact the infestation of a boll commences with the tiny caterpillar entering the boll at its base through a minute hole. Inside the boll, the caterpillar excavate a long sinuous tunnel eating away tissues on its ways and damaging the lint badly.
It finally reaches to seed which it tunnels and feeds on the nutrient available in the seeds. It should be pointed out here that the caterpillars of this pest unlike those of Earias fabia never attack the shoots. In addition to cotton, lady’s finger (Okra), Hollyhock etc. also serve as suitable hosts for this pest.
The adult moth is dark brown in colour 8-9 mm spread across the wings, with irregular black margins on the forewings. The hind wings are silvery grey and both wings are fringed with long hairs posteriorly. The tips of hind wings are sharply pointed.
The female lays elongate, oval eggs about 0.5 mm long and 0.25 mm. broad. They have minute longitudinal zigzag ridges and they are laid either singly or in groups on or near a bud or boll. The eggs which are green at first turn yellowish brown gradually and hatch in about 4-10 days into small active yellowish caterpillars. Soon after emergence the young caterpillars starts attacking the crops. They gradually become pink in colour hence, called “pink bollworm” and they bore into bolls and webs together two seeds to make a resting place especially for hibernation.
This feature of two seeds attached together is known as “double seeds” and in this condition the entire larval life is passed lasting for about 2-4 weeks. This is followed by pupation inside a flimsy silken cocoon in the soil or within the boll but outside the seed. The pupal period lasts about 10-14 days when the adult moth emerges. There are several generations in a year.
The most effective method of physical control is the heat treatment in which the infested cotton seeds are heated to a temperature of 65°C for 30 seconds. This will kill all the caterpillars inside the seeds.
Chemical control involves the use of endosulfan 35 EC @ 1.25- 1.50 litres/ha in 1000 litres of water. Rest of the insecticides used are same as for spotted boll worm.
8. Indigo Caterpillar:
Spodoptera Exigua Hubner (Lepidoptera- Noctuidae):
It is a polyphagous insect pest. It has been referred to as the indigo caterpillar because in earlier days when the indigo industry was flourishing, this pest used to be quite injurious to young indigo crop. The damage is caused by caterpillars which are gregarious, moving in swarms and destroys the young leaves of jute. It is also a minor pest of rice, cotton, tobacco, gram, maize etc.
The eggs are laid in clusters (up to 200 eggs) on the leaves. The egg clusters are covered with buff coloured hairs. The eggs hatch in 2-4 days. The larvae are blackish and there are six instars. Larval development takes 15-20 days. Pupation takes place in the soil and lasts for about 6 days. The adult is a small brown moth of wing span upto 25 mm. and they live for 8-10 days. The total life cycle is completed in about 21-30 days. There are several generations in a year.
Cultural methods of control such as ploughing and burning the crop stubbles, flooding the infested field and the removal of weeds, all help to lower the pest population. The adult caterpillars can be controlled by spraying endosulfan 35EC @ 450-1500 ml/ha mixed with 500-1000 litres of water depending up on the severity, growth and type of caterpillars.
9. Sunnhemp Hairy Caterpillar:
Utetheisa Pulchella Linn. (Lepidoptera- Arctiidae):
The caterpillar is known as “Sunnhemp hairy caterpillar”. The caterpillar feeds on the leaves and capsules. The adult moth is creamy white with black and red spots on the fore wings and dark black spots on the margin of the hind wings. The full grown larva measures about 3.8 mm. in length and is provided with red, white markings on the body, the head is slightly brown in colour.
Life History:
The female moths lay small whitish eggs on the tender leaves and shoots. Newly hatched larvae feed on the leaves. In the mature crop caterpillars feed on pods. Pupation takes place in the leaves as well as in the soil. The entire life cycle is completed in about 5 weeks. There are several generations in a year.
The caterpillars can be controlled by spraying the crop with endosulfan 35 EC @ 1.5 litres/ha in 1000 litres of water. The caterpillars and moths can also be destroyed by hand picking.
10. Jute Semi-Looper:
Anomis Sabulifera Guen. (Lepidoptera- Noctuidae):
It is a specific pest of jute and is the most destructive in the jute tracts of India and neighbouring countries. It is considered to be the most serious pest of jute foliage. The infestation is said to come about in three successive waves of which the middle one is the most injurious. The apical buds of the plant are most vulnerable and the intensity of infection tends to vary inversely with the age of the foliage.
Life History:
The pest hibernates during winter in pupal stage in the soil and the moths emerge with the first moist warm weather. The moths lay eggs on the jute plant singly particularly on the underside of the young leaves. The eggs look very much like a tiny drop of water on the leaf. There may be several such eggs on each leaf. A single moth can lay more than 150 eggs. The egg period lasts for about 2 days after which a small, green caterpillar hatches out.
The tiny caterpillars on emerging start feeding on the apical leaves and the buds. The full grown larva is about 4 cm. and it attains this size after 5 moults during a period of about 2-3 weeks. The pupation may take place on the plant or in the soil. The pupal period lasts for only a week or so after which the moths emerge and begin to produce the next generation. The whole life cycle takes about one month, thereafter several generations are completed in a year.
Control:
The pest can be successfully controlled by spraying the crop with methyl – parathion 0.04%. Spraying endosulfan 35EC @ 450-1500 ml/ ha mixed with 500-1000 litres of water is also very effective.
11. Jute Stem – Girdler:
Nupserha Bicolor Postbrunnea Dutt (Coleoptera- Lamiidae):
This pest was reported to be serious on jute crops. The main damage is caused by the adult beetle while preparing sites for egg laying on the stem. It is distributed throughout the jute belt in India.
The female while preparing for laying eggs, cuts with the help of its sharp mandibles, two rings around the stem so that the distance between these two rings is generally 1-1.4 cm. and thereafter it makes, with its mandibles again a slit on the stem between these two rings. The depth of this slit reaches down to the pith level where a single egg is deposited.
The average number of eggs laid per female is 35, hence the same number of jute stems are damaged within 2-3 weeks. The eggs are yellowish, about 1.5 mm. long and 0.5 mm. broad. They hatch in 3-4 days. On hatching, the larvae travel downwards along the central hallows area, resulting from the disintegration of the pith. The total larval period during the normal jute season varies between 30-50 days. The mature larva measures about 1.4 cm. and at the advent of winter the larva enters the diapause phase.
Before pupation or diapause, the larva makes a pupal chamber within the hollow of the stem. The diapause phase lasts till a favourable combination of environmental factors is obtained during the following summer but under unfavourable conditions it may last for several years. The pupa closely resembles the adult beetle in form and size. It measures about 0.8 cm. The emergence of the adult largely depends on the time and amount of rain fall.
The jute girdler can be controlled by spraying methyl demeton 25 EC @ 800 ml/ha or dimethoate (Rogor) 30 EC @ 600 ml/ha in 500 litres of water.
12. Jute Stem Weevil:
Apion Corchori Marshall (Coleoptera- Apionidae):
This stem borer is a weevil which is also commonly called the jute Apion. The weevil can cause appreciable damage to early sown jute or where the crop is grown for seed. It damages the quality of the jute fibre. The female weevil bores holes for oviposition by means of its rostrum in the jute stem.
A single female has been observed to lay upto to 675 eggs during a period of 124 days. On an average an egg measures about 0.43 mm. in length and 0.33 mm. in breadth. The larvae emerge after 3-5 days and start feeding on the surrounding tissues. They are full-fed in 8-11 days. The full grown grub is about 2.85 mm. in length and about 1 mm. in breadth. The grub period may be as short as 8 days.
The mature grub makes a rough chamber inside the stem and pupates therein. The pupa measures about 2.1 mm. in length and about 1 mm. in its maximum breadth. The pupal period may be 4-6 days after which the adult weevil emerges from the pupal case through an exit which is either made by the larva before pupation or by the weevil itself.
The adult is a tiny weevil about 1.8 mm. in length and 0.8 mm. in breadth with a very conspicuous snout. It is dark brown or dull black in colour clothed with small whitish setae. The whole life cycle can be completed in about 15-24 days, but the maximum longevity of the adult has been reported to be as much as 209 days.
Thus, there are a large number of over lapping generations during the jute season. Winter is generally passed in adult stage and the weevils concealing themselves in various bushes, shrubs and hedges and start laying eggs on the new crop next year.
The pest can be controlled by spraying the crop with methyl parathion 0.03% which kills the grubs inside. The jute stem weevils both adults and caterpillars can be controlled by spraying endosulfan 35 EC @ 450-1500 ml/ha mixed with 500-1000 litres of water depending on the growth stage and type of caterpillars. The pest may be suppressed by removal and destruction of infested plants and by collecting and destroying the stubble after harvest.