Management of insect pests of cotton

Cotton is one of the most important commercial crops of India. Cotton crop is infested with different kinds of insects in the production cycle. Jassids, thrips, aphids and whiteflies are among sucking pests and bollworm (American and spotted) and spodoptera caterpillars which attack on leaves and bolls.

American bollworms can cause upto 40 -50 % crop losses in severe incidences. The high resistance in American bollworms towards the insecticides is/was challenging and scientific research have developed transgenic cotton hybrids popularly known as Bt Cotton.

Bt cotton hybrids have excellent control of American boll worm and insecticides may not be required to use on cotton crop to control this boll worm.

Insect pests of Cotton

1. American boll worm (Helicoverpa armigera):

The larvae of boll worms will feed on the inside contents of bolls making holes and larva’s head will be inside and body be outside. The feacal pellets will be seen on the bolls. Each larva of American boll worm can damage up to 30 – 40 bolls. Minimum infestation of this Helicoverpa armigera or American boll worm is noticed on transgenic Bt Cotton varieties.

2. Pink bollworm (Pectinophora gossypiella Saunders):

Pink boll worm feeding behavior is similar to American bollworm infestation. When the pink boll worm attacks the flowers making them irregular shape more or less like rose flowers usually called the rosette. Worms feeds inside the bolls, seed kernels and the entry holes will be covered with their fecal matter. Boll dropping is noticed due to the pink bollworm attack.

3. Tobacco caterpillar (Spodoptera litura Fab.)

Spodoptera litura moths will lay eggs on the young plants, larvae hatch out consume the epidermal layer of the leaves leaving the leaves mesh like. Severe infestations may also lead to total defoliation.

Recently another species of Spodoptera, the army worm Spodoptera frugiperda have become a very serious insect which may also infest on young cotton plants cutting the germinated cotton plants.

4. Spotted bollworm (Earias insulana and Earias vitella Fab.)

Spotted boll worm larvae directly feeds on the cotton squares, flowers, bolls and sometimes on the shoots. Spotted boll worms can damage the cotton plant branches in vegetative phase causing the terminal shoot drying and dying. When these boll worms attack on the bolls holes are formed and they get rotten.

The boll worm complex other than the American boll worm may be controlled by using the following chemicals with proper usage methodologies.

5. Jassids (Amrasca biguttula)

Cotton plants are also infested by jassids in the leaves making them pale coloured by sucking sap, leaves turn downward and plants grow very slow. the leaves turn downwards and colour of the plant turns pale.  

In case of severe infestations marginal chlorosis of the leaves is noticed.

 6. Cottonaphid (Aphis gossypii)

Aphids also infest on cotton crop. The young growing tips die, leaves will shrink and may bend backwards.

The gum like honey dew is noticed on the infested branches and leaves later Black sooty mould is formed due to the excretion from the fungi after consuming the honey dew excreted by aphids.

 7. Thrips (Thrips tabaci) of Cotton.

Thrips are another sucking insect type which suck the sap of the young cotton leaves, the leaves turn yellowish to pale green.

The younger leaves turn upward with reduced size and severe infestations may make the leaf edges turn brownish burnt like.

8. Red cotton bug: Dysdercus cingulatusi

Red cotton bug adults and older nymphs feed on the emerging bolls and later they may also attack on the cotton seeds.

Bugs may also transmit cotton fibre staining fungi or bacteria which reduces the quality of the cotton fibre. The lints turn red, bolls may rot turning black.

The molecule listed below may be used in the management of above pests

8. Whitefly: Bemisia tabaci

Cotton crop is also infested by whitefly and they attack the young plants, sucks the juice and like aphids simultaneously excretes the honey dew on the leaves and there will be development of sooty mould which leads to reduced photosynthesis as the leaves will be covered with black mould.

Many viral infections can be transmitted by whiteflies from plant to plant and fields to fields.

Management of Whiteflies

9. Mealy bugs: Phenacoccussp, Ferrisa sp and  Maconellicoccus sp 

Mealy bugs are also common sucking pests in cotton crop. Mealy bugs are found in clusters under surface of the leaves with waxy secretion.

Sooty mould is also noticed in the plants with mealy bug infested plants. Plants become weak and yields will be reduced if not managed.

Management of Mealy bugs in cotton:

• Weeds are always the alternate hosts and proper sanitation, weed free farms will have minimum infestations.
• Continuously monitor the incidence and early detection will help to manage effectively
• Use of Encyrtid parasitoids, Acerophagus papayae @ 100 per village against Paracoccus marginatus and Aenasius bambawaeli against Phenococcus solenopsis are recommended.

 11. Mite pest on cotton

Red Spider Mite: Tetranychus Cinnabarinus (Tetranychide acarira), Yellow Mite / Broad Mite: Polyphagotarsonemus latus (Tarsonemidal acarina) and Wolly Mite : Aceria gossypii  are three types of mites which usually infest cotton crop. The mites attack cotton plants at early stages of crop growth normally found under surface of the leaves sucking the sap.

Many times the mites produce web and they tend to live inside the web. The leaves show the chlorotic patches on the leaves where the mite infestation is noticed.

Management of mites in cotton

              ****

K SANJEEVA REDDY,

Senior Agronomist, BigHaat. 

For more information kindly call on 8050797979 or give missed call on 180030002434 during office hours 10 AM to 5 PM

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