Identification of insect pests of Cotton and their damage symptoms

Dr. M. Thippaiah professor Dept. of Entomology College of Agriculture GKVK, UAS Bangalore- 65

It is a important fiber crop in India and also high valued commercial crop for textile industries India occupies the largest area in the world under cotton and it ranks third in production At present this crop is grown in an Area- 12.18 million ha Production- 13.73million bales (170kgs each) All the 4 spices of cotton i.e.

Gossypium herbaium G. herborium G. hirsutum G. barbadens

are grown in India commercially that's why India is much important in cotton cultivation Factors that affects poor yield in cotton

Cultivation in rainfed condition

Timely not taking plant protection measures

Use of high yielding varieties- attracts more pest

Indiscriminate use of pesticides particularly broad spectrum pesticides leads emergence pests

Maximum pesticides consumption In cotton – 52.58 % Rice - 24 % Pulses - 17.18 %

60 % of total pesticides produced are diverted to cotton because of this

Pest resurgence – only the crop where in synthetic pyrethroids are recommended Main problems of synthetic pyrethroids are Resurgence of white flies in 1995 in AP Resurgence of Helicoverpa in 1988-89 in AP To avoid this they recommended only 2-3 sprays of pyrethroids alternated with conventional insecticides

Change in species composition Environmental pollution Health hazards Destruction of natural enemies Most of the insects develops resistance

Crop loss – 50-60 % due to insect pests

In India expenditure on plant protection i.e. pest control on varalaxmi hybrid ranges from 43-72 % i.e. 12-25 sprays are taken up to control different insect pests

There are more than 1326 species of insects have been reported attacking cotton in the world. However, in India only 162 species have been recorded ,

Among which 14-15 species may be called as major pests due to their occurrence in serious proportions almost every year

Insect pests of cotton are classified as

Sucking pests

Boll worms

Defoliators

Root / Stem feeders or Borer pests

Non insect pests

1 Leaf hopper Amrasca biguttula biguttula Cicadellidae Hemiptera

2 Aphids Aphis gossypii Aphididae Hemiptera

3 Solenopsis mealy bug

Phenacoccus solenopsis Pseudococcidae Hemiptera

4 White fly Bemisia tabaci Aleyrodidae Hemiptera

5 Thrips Thrips tabaci Scirtothrips dorsalis

Thirpidae Thysanoptera

Cotton stainers6 Red cotton bug Dysdercus cingulatus Pyrrhocoridae Hemiptera

7 Dusky cotton bug Oxycaraenus hyalinipennis Lygaeidae Hempitera

Sucking pests of Cotton

Leaf hopper : Amrasca biguttula biguttula ( Cicadellidae : Hemiptera)

It is a major pest in all cotton growing region of India Introduction of American cotton the leaf hopper become severe in 1970’s and J.K series are also more susceptible to leaf hoppers Favourable conditions for multiplicationDry weather or cloudy weather in South India ideal for multiplication of leaf hoppers

Adults are small, measures 2-3mm in length, wedge shaped hoppers and green in colour with black spots on the head and posterior end of

fore wings

Nature and symptoms of damage Both nymphs and adults suck the sap from under surface of leaves as a result tender leaves turn yellow, the leaf margin curl down wards, margins become yellow in the beginning and later reddish in colour and starts drying

In severe cases, leaves get a bronze or brick red colour which typical ‘hopper burn’ and crop growth retarted

The infestation occur in seedling stage and seedlings gets killed, the number of flowers and bolls are reduced

Life Cycle of the pest Eggs : are laid singly with in leaf veins and epidermis on upper surface of the leaf Matured leaves of one month old crop are more preferred for egg laying Each female lays – more than 20 eggs I.P – 4-11 daysNymphs – there are 4 nymphal instars Nymphs are light green in colour and translucent found between veins of leaves on ventral surface N.P – 7-21 days Total life cycle- 15-45 days

There are 11 generations / year

Leaf curl down wards, margins become yellow in the beginning and later reddish in colour and starts drying

Symptoms The leaf gradually dries up and drops The plants become stunted The number of flowers and bolls production gets reduced The quality of cotton lint is also reduced The loss of plant vitality, there will be up to 35 % in yield

Aphids : Aphis gossypii ( Aphididae : Hemiptera)

Adults are soft bodied, yellowish green in colour, winged or wingless insects They produce parthenogenetically / Ovo-viviparously They produce – 8-22 nymphs/ day/female Nymphs: there are 5 nymphal instars, N.P – 2weeks

Nature and symptoms of damage

Nymphs and adults suck the sap from the tender shoots and leaves as a result Plant cause stunted growth, gradual drying and leaf curl down wards and finally death of the plants

Infestation occur both in the early stage and later stage They also excrete lot of honey dew and sooty mould development takes place on the leaves and plants are dark appearance

The damage is more severe in young seedlings

Solenopsis mealy bug : Phenacoccus solenopsis ( Pseudococcidae : Hemiptera )

P.Solenopsis has emerged as a major pest of cotton in the Northern zone, causing heavy reduction in yield.

P.Solenopsis has two dark stripes on either side of the middle ridge of the body is a distinctive character of females

Dark stripes

It takes 25-30 days to complete one generationA female adult produces about 150-600 eggs in the ovisac and within 3-9 days the crawlers come out and actively move and spread out and settled down for food on plant parts and gradually develops waxy coating

Nature of damage The insect sucks the sap from almost all parts of the plant including leaves, stems, exposed roots and fruiting bodies, thus considerably weakening these parts

The shoot tips develop a bushy appearance and the entire plant may become stunted

In affected plants bolls are few in number, deformed and small in size

The pest secrete sweet honey dew, which encourages the development of black sooty mould, adversely affecting photosynthesis

Ants attracts by the honey dew, have been observed carrying mealy bugs from plant to plant

White fly : Bemisia tabaci ( Aleyrodidae : Hemiptera )

Adult white flies Adults fly

Both nymphs adults congregating on the under surface the leaf

Adults are small soft bodied, yellow coloured insects with Wings and body are dusted with white waxy coating

It is a polyphagous pest it attacks bhendi, potato, tomato etc., In early days it is a minor pest and in 1980’s on wards it become a major pest

Life cycle of the pest

Eggs : stalked eggs laid singly on the lower surface of the leaves Each female lays 120 eggs I.P – 3-5 days

Nymphs : First instars are very active , highly mobile are called as crawlers and greenish yellow in colour Second and third instar nymphs are flat, scale like and immobileAfter fourth moult it stops feeding, and 4th nymphal stage is pseudopupal stage and extends 2 days N.P -5-33 days

Total life cycle – 45-50 days when temp. 40-500C

Complete its development with in 15 days at 30o c

Nature and symptoms of damage Adults and nymphs insert their stylets on under surface of the leaves

and suck the sap As a result the vitality of plant and plant growth is stopped and shedding of

buds and bad opening of bolls, retention quality of lint decreases

They excrete honey dew as a result development of sooty mould and they decrease photosynthetic activity of the plant

It also transmits the leaf curl virus disease of cotton

Symptoms White chlorotic spots appear on the leaves and later join

to form irregular yellowing of leaves.

Leaves fall prematurely

Number and quality of flowers, squares and bolls gets reduced

Nymphs and adults secrete honey dew which leads to sooty mould formation

Favourable condition for multiplication of the white flies Introduction of new variety which is susceptible

to the pest Prolonged dry spell

Excess nitrogen application

Frequent irrigation and closer spacing

Indiscriminate use of insecticides, especially synthetic pyrethroids

Abiotic factors i.e Change in Temp. RH and Intermittent rainfall

Thrips : Thrips tabaci – Infests flowers

Scirtothrips dorsalis – Usually found on leaves (Thripidae : Thysanoptera )

Nymphs and adults lacerate the tissues on the undersurfaces of the leaves and suck the sap as a result shriveling of leaves and curl up and become crumbled or crinkled. When infestation is severe, we observe Silvery patches seen on lower surface in early stage of attack and brown colour in the upper surface in theadvanced stage Ragged edges / broken edges and

Finally plants are sickly appearance

Adults are small, slender, yellowish to brown with fringed wings Nymphs are very minute, slender yellowish and microscopic

Cotton stainers

Red cotton bug : Dysdercus cingulatus ( Pyrrhocoridae : Hemiptera )

Adults are bright red coloured bugs with eyes, scutellum and antennae are black in colour

Ventral side of the abdomen with white stripes

A prominent black spot is present on each side of the hemelytron

Nymphs and adults suck the sap from tender ripening bolls as well as from developing Seeds The seeds become shriken and loose its viability and quality of the lint is reduced

The proboscis of this bug will always have a bacterium, Nematospora gossypii The moment they insert the proboscis, the bacterium enter the boll and multiply and lint get discolured that why this bug also called cotton stainer

Eggs : are laid in loose soil in masses and protect with soil or dry leaves Each female lays 100-130 eggs around the base of the plant I.P – 4-7 daysNymphs : are reddish with white band on the abdomen N.P – 28-29 days Nature and symptoms of damage

Overall :

Development of bolls will be affected

Oil content of seed is reduced

Staining of the lint

Seeds become unfit for sowing

Alternate hosts:

Bhendi, Hibiscus, Maize, Sorghum etc.,

Dusky cotton bug : Oxycaraenus hyalinipennis ( Lygaeidae : Hemitera )

Adults are small flat bugs with dusky brownish in colour or blackish in colour with dusky white wings/ transparent wings

The activity starts once the bolls gets open

Nymphs and adults live together and suck the sap from developing seeds such seeds fail to ripen, they shrivel, oil content decreases The faecal matter accumulates and staining the lint black colour These will enter the storage and continue to feed and affect the quality of the lint During ginning these bugs get crushed and then lint get stained Some factors favours more incidence of the pest

Sow the crop late On ratoon crop Prolong the season

Eggs : are cigar shape, white in colour and laid in clusters of 2-10 on half opened bolls or flower buds I.P – 6-10 daysNymphs : there are 5 nymphal instars N.P – 30-40 days

Nature and symptoms of damage

Boll worms of Cotton

1 American bollworm Helicoverpa armigera Noctuidae Lepidoptera

2 Spotted bollworms Earias vittella & E. insulana

Noctuidae Lepidoptera

3 Cotton pink bollworm

Pectinophora gossypiella Gelechiidae Lepidoptera

Cotton bollworms are the most destructive group of insects found on cotton in all cotton growing areas of the world.

There are three kinds of bollworms, viz., spotted bollworms, American bollworm and pink bollworm. Among the three, the spotted bollworms occurs early, when the plant is 15-20 cm height and continues to feed on shoot.

The other two occur from square formation stage, and pink bollworm continues till picking of kapas and goes even to ginning mills

American boll worm : Heliocoverpa armigera ( Noctuidae : Lepidoptera)It is a polyphagous pest and it has got large number of alternate hosts i.e. 96 species of crops 61 species of weedsIt will keep multiplying and will be always above ETL

Damage- 40-65% of damage to cotton plant

Adult

Adults are medium sized, light brown coloured mothsFore wings- are light brown with a prominent black spots on the wingHind wing- are grey coloured with broad black patch along the apical margin

Lifecycle of the pest

Eggs- are laid singly on tender shoots, squares, flower buds, bracts, bolls I.P – 3-4 days

Larva

Pupa- Pupation takes place in soil P.P- 9-12 days Adult moth

Larva passes 5-6 instars, measures 3.5 to 4.0cm in length, variously coloured / different colour morphs, palegreen, dark green, pale brown, dark brown and can be recognized by a yellowish line on either side of the body L.P- 30-40 days

Nature and symptoms of damage In the early stage – the larva feeds on tender leaves

later bores in to squares or young flower buds and developing bolls and feeds internally as a result the buds and young bolls flare up and finally drop off

Larva habit of putting of head and thorax inside the boll and remaining body out side with this habit it has potentiality of destroying more bolls than what it feeds

Entry hole don’t be plugged with excreta(large entry holes) a single larva can damage more of bolls

Matured bolls does not drop-off one or two locules will be affected

Microorganisms will colonize and colour the lint and larva usually feed on the seeds In the initial stage the incidence is low but once the crop producing boll its incidence is high and it will continue till harvest

Larva fed on flower

Larva feed on flower bud

Larva habit of putting of head and thorax inside the boll and remaining body out side with this habit it has potentiality of destroying more bolls than what it feed.

Entry hole don’t be plugged with excreta

Spotted boll worms or Spiny boll worms1.Earias vitella ( Noctuidae : Lepidoptera )2. Earias insulana

Adult moth of E. vitella Larva and adult of E.vitella E. vitella

More predominant in South India, especially in high rainfall area Fore wings are yellowish white with wedge shaped green band in the

middle from base to outer margin Larva : light brown with white patches and ventral aspect green in colour and body covered with bristles / setae

These two species are the most important pests of cotton causing heavy loss to the crop every year Damage loss : 40-50 % of young shoots, 50-57 % of bollsThese are small to medium sized moths, measuring 25mm in length

Fore wings are yellowish white with wedge shaped green band in the middle from base to outer margin

Larva Adult

Earias vitella

Earias insulana

More predominant in North India i.e areas where receiving scanty rains

Fore wings are completely green in colour

Larva : Dull greenish white in colour with No. of black markings and orange coloured dots on prothoracic region

Life cycle of the pest

Eggs – are laid singly or in groups of 2-3 on tender leaves, squares, young shoots, bolls Each females lays 63 - 700 eggs I.P – 3-10 days

Caterpillars are light brown in colour with white patches or markings, ventral aspect green in colour and measures 1.5- 2cm in length and body covered with bristles or setae

Larva dull greenish white and number of black markings and orange coloured dots on prothoracic region L.P- 9-20 days in warm weather 50-60 days in winter

Pupa- Pupation takes places out side the bolls in tough boat shaped dirty white silken cocoon or on the plants , fallen leaves or soil or base of the plant P.P – 4-87 days depending on temp.

Nature and symptoms of damage The newly hatched larva bores in to tender shoots during vegetative stage feeds internally as a result infested shoots withers, droops and dries

During reproductive stage- They bore into the buds , flowers and bolls and feeds internally as a result infested buds, flowers and bolls drop down

Bored holes on bolls plugged with excreta and entire inner content of square totally fed and quality can be destroyed

Symptoms Drying and drooping of young shoots

Shedding of buds, flowers, bolls, flaring of bracts

Bored holes on bolls are plugged with excreta

The newly hatched larva bores in to tender shoots during vegetative stage feeds internally as a result infested shoots wither.

Bored hole are plugged with excreta

Pink boll worm Pectinophora gossypiella ( Gelechiidae : Lepidoptera )

Adult is a dark brown moth and measure 1 cm in length.Fore wings- are narrow, trapezoidal in shape

Hind wings- are round to wards apical margin

Both fore wings and hind wings are fringed

Life cycle of the pestEggs : female moth lays small flat eggs singly on the tender leaves, flowers, squares and developing bolls Each female lays 400 eggs I.P – 4-25 daysLarva : there are 3 larval instars First instars and second instars larvae are green in colour and later instars, smooth pinkish coloured body with brown coloured head L.P – 8-41 days Pupa : the fully grown larvae pupates among fallen leaves, debris, dropped bolls, under clods of soil P.P- 10-15 days Climate plays an important role in determining the abundance of the pest

Moderate temp.

Cloudy weather

Moderate rains

Nature and symptoms of damage Larvae feeds on leaf tissues and later bores in to flower buds, flowers bores in to the bolls First brood develops by feeding on the anthers, style and occasionally on ovaries in the flower buds When they are found on flowers, the flowers do not open and give ‘ rosette appearance ’ Subsequent broods develop within young and matured bolls, and entry hole not visible out side and they feed on inner contents thus affecting bolls, flowers, young infested bolls drop down and finally lint become black colour Symptoms Premature shedding of flower buds and bolls

Infested flowers are rosette appearance or clustering together

Premature opening of the bolls

Lint quality declines and seed germination reduced

Presence of interlocular burrow in the opened bolls

Pectinophora gossypiella

Adult moth rosette appearance of flower

Early instar

Larval feeding Grown up larva Damaged boll

Larva inside the matured boll Larva feeds inner content