Cotton is the world’s leading fibre crop and is called as white gold. Cotton production, processing and its trade provide livelihood and employment to millions of people worldwide. Export of raw cotton earns valuable foreign exchange. So this is a good cash crop for farmers.
Cotton is affected by several insects from seedling stage to maturity stage which cause severe economic loss to farmers. Timely plant protection with appropriate products helps in preventing the damage to crops by the insects.
We may classify different insect attacks to the cotton crop, according to the growth stage of the crop. Which will be easier for farmers to identify the particular pest attack at particular growth stage of crop and can take appropriate prevention measures.
Major insect pests of cotton
The insect pests of cotton are broadly classified as sucking insect pests and cotton bollworms.
Sucking insects of cotton
These groups of insects suck the cell sap from different plant parts resulting in stunted growth of the plant.
Examples are : Thrips, Jassids, Aphids, Whiteflies, Red cotton bug, mealy bug.
Cotton Bollworms
These groups of insects mainly attack the cotton reproductive parts like flowers, bolls and hamper the cotton production.
Examples are: spotted bollworm, helicoverpa, spodoptera (tobacco caterpillar), semi looper, pink bollworm
Cotton insect pests are further classified as their time of attack in different growth stages of the cotton plant as given below.
Sucking insect pests of cotton
Cotton Aphids
Cotton aphids are small, slow moving insects that feed primarily on the underside of cotton leaves.
Nymphs are small and blackish. Aphids live in colonies and reproduce parthenogenetically.
Nymphal stage lasts7 to 9 days & adults live for 12 to 20 days and there may be 12 to 14 generations in a year.
Nymphs and adults suck sap from the leaves, twigs and buds. The leaves wrinkles and curls.
Aphids excrete honeydew which encourages black sooty mold growth. Honey dew attracts ants.
Spray Imidacloprid 17% SL@ 100ml/acre or Thiamethoxam 25% WG @ 50-80grams/Acre.
Cotton Jassids
Jassids attack during 1to 50 days of age and the attack is severe in low temperatures 20 - 25º C.
Nymphs and adults are greenish yellow in colour.
Both nymphs and adults suck sap from the underside of the leaves. Leaves turn yellow in colour and curl downwards and dry up when infestation is severe.
Spray Imidacloprid 17% SL @ 100-150 ml per acre or Acephate 75% SP @ 300-350Gram/acre.
Cotton Thrips
Thrips are one of the most common early seedling pests on cotton.
Thrips suck sap from the leaves causing leaf curl affecting photosynthetic activity.
severe infestations may make the leaf edges turn brownish burnt like,plant tip loss or seedling death.
Spray Bifenthrin 10 % EC @ 350-400 ml per acre or Spray Imidacloprid 17% SL@100-150 ML per acre.
SOME PESTICIDES FOR CONTROLLING COTTON APHIDS,THRIPS AND JASSIDS ARE
Cotton whiteflies
Whiteflies are small, powdery white insects found on the undersides of leaves.
White flies feed on cell sap of leaves interfering photosynthesis.
Due to the excretion of honeydew,sooty mold formation occurred all over the surface of the leaves.Also lint of opened bolls result in blackening of lint.
Very Important is to maintain nutritional balance: (N2 strictly to be used as per recommendation).
1st application: Spray Acetamiprid 100-200 gram/ acre depending on crop canopy.
2nd application Diafenthiuron 50%WP @ 250gr per acre.
As an added advantage Acephate may be mixed with any of the chemicals @400gr per acre.
SOME PESTICIDES FOR CONTROLLING COTTON WHITEFLIES ARE
Red spider mite
Red spider mites attack cotton in early and later stages also.
They are generally found on the undersurface of leaves and wire fine webbings. During heavy infestation the mites may be found all over the leaf surfaces.
Mites puncture the leaf tissue and suck the plant sap.
Removal of plant sap, chlorophyll and other plant pigments results in reddish bronze discoloration of leaves.
Severe infestation leads to premature defoliation of leaves.
SOME PESTICIDES FOR CONTROLLING COTTON RED SPIDER MITES ARE
Red cotton bug
Red cotton bugs are more active in September and October.
Eggs are laid in moist soil or in crevices in the ground, hatch in 7-8 days and reddish orange nymphs emerge, nymphal period is for 5-7 days. The life cycle takes 50 to 90 days.
Nymphs and adults suck sap from leaves and green bolls, stain the lint with their excreta or body juices that gives way for growth of bacteria and fungi. They are also called stink bugs because of the foul smell they emit.
For effective control spray (CHLORPYRIPHOS + CYPERMETHRIN) @ 300ml/acre Or Bifenthrin @ 400ml/ per acre.
Mealy bug
Adults and nymphs weaken the plants by sucking sap from leaves, twigs, stems, roots and fruiting bodies.
Bolls are deformed, fewer in number and smaller in size in affected plants.
Honey dew secreted by the pest encourages development of black sooty mould which adversely affects photosynthetic activity.
Cotton mealy bugs can be controlled by spraying Thiamethoxam 80-100gr or along with Diafenthiuron 250gr/acre along with detergent or Shampoo or Imidaclprid @100ml per acre.
SOME PESTICIDES FOR CONTROLLING COTTON MEALY BUGS ARE
Cotton Bollworms
Spotted bollworm
Moths lay eggs on flower buds, branches and twigs.Eggs hatch in 3-4 days.
Caterpillars cause damage by boring into the growing shoots, buds, flowers and bolls.
The attacked shoots become dry and ultimately die.
Flowers and buds dropped off. Infested bolls do not mature properly and open prematurely and quality of the lint is spoiled.
The best way to control this insect is at egg hatching and first instar larva stage by spraying Chlorpyriphos 50% + Cypermethrin 5% @ 300-400 ml per acre or Chloropyriphos 50% EC @400 ml per acre.
In case significant infestation use Emamectin Benzoate 5% SG @ 80-100grams per acre.
Helicoverpa
Heliothis is a polyphagous insect.
Eggs are laid on tender parts of the plant. Egg stage is 3-5 days. Larvae stage is 17-35 days. Pupal stage is 17 to 20 days.
Moths are about 19 mm long, with a wing span of 25-37 mm. Eggs are spherical in structure.
A single caterpillar can damage 30 to 40 bolls.
It is most ideal to control this insect at egg stage itself to avoid crop loss.
Helicoverpa infestation has been arrested with the introduction of Bt-II technology in Cotton in India.
In a few cases where F2 seed/ Spurious Bt seed is used, Helicoverpa infestation may appear.
Spray Bifenthrin 330ml +Acephate 75% SP 330gm /Acre or Emamectin Benzoate 5% SG @100gram/acre.
Spodoptera (Tobacco caterpillar)
The eggs are laid on the under surface of the leaves near midrib, hatch in 5-8 days.
The caterpillars are pale green in colour, with dark brown bands.
Larval period 20 to 30 days. Pupation occurs in soil or in plant debris. Pupal period 7to 15 days.The life cycle is completed in 50 to 60 days.
The larvae feed heavily on the under surface of the leaves and skeletonize them leaving only the midrib and veins.They also attack flowers, buds and squares causing considerable loss.
For effective control of larvae spray Emamectin Benzoate 5% SG @80 to 100gr/acre or (Chloropyrifos 50% + Cypermethrin 5%) @300ml/acre.
Semi looper
The larvae congregate in groups and move actively.
They Feed on leaf lamina making small holes on leaves.
The grown up larva feed voraciously and leave only mid ribs and veins.
In severe cases, they attack flowers, buds and squares.
spray Emamectin Benzoate 5% SG @80 to 100gr/acre or (Chloropyrifos 50% + Cypermethrin 5%) @300ml/acre.
Pink bollworm
Pink Bollworm Larvae feed on developing and mature bolls, especially on the seed.
When the larvae puncture the flower bud, the flower does not open fully.
When the pink boll worm attacks the flowers, making them irregular in shape more or less like rose flowers usually called the rosette.
Full grown larvae are about 1/4 inch in length and are pink in colour. Younger larvae of the pink bollworm are white in colour, and are difficult to see in the lint of developing bolls.
The small pupa is also commonly found inside mature bolls, or inside seeds of ginned cotton.
Worms feed inside the bolls, seed kernels and the entry holes will be covered with their fecal matter.
Boll dropping is observed due to the pink bollworm attack.
Life cycle-Egg stage – 4 to 25 days, Larval stage 8 to 41 days,Pupae 6 to 10 days and Adult 4 to 5 days. In a year there would be 4 to 6 generations.
spray Emamectin Benzoate 5% SG @80 to 100gr/acre or (Chloropyrifos 50% + Cypermethrin 5%) @300ml/acre.
SOME PESTICIDES FOR CONTROLLING COTTON BOLLWORMS ARE
Minor insects of cotton
Cotton nematodes
In low fertile soils where cotton is repeatedly cultivated, nematode damage becomes a common problem.
In case of severe infestation plant growth will be hampered.
If the plants are uprooted one can see the gall formation on roots at the early stage of the cotton crop.
Apply Fipronil @ 8-10 kg per acre.
Regular application of compost /FYM / Green manure will reduce the nematode infestation in the long run.
Cotton Gray weevil
Normally it is a minor pest but sometimes it becomes a serious problem for the plant.
Grey weevil appears mostly during April to July month.
Adults are greyish in colour, 4-5 mm long with protruding snout. The life cycle is completed in 42 to 65 days.
The grubs and adults feed on roots of cotton seedlings and hamper the crop growth.
At a later stage adults feed on leaves, buds, flowers and young bolls and make round holes.
Apply Cartap Hydrochloride @ 8 kg -10 Kg per acre.
DISCLAIMER: The above recommended pesticides and their doses are for education and information purpose only. Please follow proper pesticide application guidelines, local agriculture experts advice and other recommended criteria before application to crop.
CONCLUSION
Cotton is a good cash crop which gives good economic benefits to farmers. But it also attracts certain insect pests which hamper the crop production. Following proper pest control measures in particular time will minimize the insect pests attack and give better economic results.
Hope this article may give certain information about cotton insect pests and their management. Please give your valuable feedback here and share the article.
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