Cotton is an important cash crop in Pakistan, which is the fourth largest cotton producer in the world after China, India, and the United States. Cotton is a good source of fibre and edible oil, but in Pakistan, the average yield is poor as compared to other countries. The infestation of many harmful insect pests is the main cause of its low yield. The cotton crop is home to a variety of insects, the most damaging of which is bollworms and sucking pests. Despite the replacement of traditional cotton with Bt cotton, which resulted in successful control (85–90%) of cotton bollworms, sucking insect pest infestations persist.
Pests of cotton
Pest can reduce cotton yield by up to 70-80%.
Chewing pests of Cotton
- American bollworm
- Pink bollworm
- Spotted bollworm
- Armyworm
Sucking pests of Cotton
- Whitefly
- Aphid
- Jassid
- Thrips
American bollworm
The larvae are voracious eaters, and their attack on cotton begins as soon as the monsoon rains arrive. From the inside, an attack hollows out the square, preventing it from developing into flowers. A single larva can damage 10-12 buds, leaves, squares, and bolls. The attacked boll has large holes in it, indicating that it has been attacked. Outside the borehole, there are granular faecal balls. The fruits stop developing, mature quickly, and then fall off.
Spotted bollworm
The larvae bore into the terminal portion of the shoot when the cotton plants were young, causing them to wither and dry up. Later, the larvae cause damage to cotton flower buds, flowers, and fruits by boring into them. The bolls that have been attacked openly prematurely and larval feeding spoils the lint.
Pink bollworm
Larvae enter in squares, which then bloom into Rosetted flowers. Later, the larvae that invade the bolls leave no visible evidence of their presence. The entry point becomes bulgy. Damaged bolls fall off early, and those that do mature develop lint of inferior quality. A symptom of the attack is the formation of double seeds. Pink bollworms account for half of the overall damage caused by all bollworms.
Armyworm
The caterpillar is the only one that causes damage. For the first few days, eat gregariously, then disperse to feed individually. They eat plant leaves, especially the green fleshy area of new growth in between the veinlets, leaving the skeletons of the leaves behind. The skeleton dries up and crumbles to the ground.
Aphid
Aphids attack terminals, leaves, buds, and stems from early to late in the season. The pest’s nymphs and adults feed on the tender parts of plants. When there is a serious attack, the plant becomes weak, the leaves curl up, the plant dries out, and eventually dies. Aphid honeydew has the potential to contaminate lint.
Whitefly
Feed on plant sap, causing plants to wilt, drop leaves, and even die under extreme pest pressure. secrete honeydews, which encourage sooty mould, which decreases crop yield potential by blocking sunlight and decreasing nutrient assimilation. The transmission of the cotton leaf curl virus (CLCv) is carried out by this insect.
Thrips
Terminals, leaves, buds, and stems are all damaged early in the season by nymphs and adults. Severe damage causes the rising point to be destroyed (tipping out), resulting in lateral branching. In hot and dry weather, it is a serious pest. Leaves become wrinkled and fall off in extreme infestations, causing premature boll opening. The leaves of infested plants turn a silvery-white colour.
Jassid
Both the nymph and adult Jassids damage cotton crops. They suck the cell sap from the leaves undersides and inject poisonous material into the leaf. As a result of the attack, the leaf turns yellow or brownish, the margins curl downwards, and the leaves eventually fall.
Control measures
Non-chemical control
- Reduced the amount of fertilizer used.
- Weed eradication
- Remove previous crop stubbles, as they harbour many insects and pathogens.
- To uncover the pupated larvae and eggs, deep ploughing should be recommended.
- Caterpillars are hand-picked.
- Avoided the cotton sowing before April 15th.
- Use egg parasitoid trichograma chilonis
- Predators include chrysoperla carnea, encarsia spp. and ladybird beetle
Seed treatment
Delinting can be accomplished with either concentrated sulphuric acid or imidacloprid 70WS. This kills the hibernating larvae and ensures that the seed is distributed evenly during sowing. Delinted seed is handled with fungicides such as Actara ST 70 WS, Dividend Star 036 FS, and Dynasty CST 125 FS, or any other appropriate fungicide.
Resistant varieties
Sowing can be done with CCRI Multan varieties like CIM-663, CIM-632, CIM-602, CIM-600, CIM-177, CIM-178, and CIM-179, as well as CCRI Sakrand varieties like CR1S-129, CR1S-510, CR1S-585, CR1S-543, and CR1S-613.
Chemical control
For sucking insects
- Nurelle D 505EC 500 ml /acre
- Polo 500SC 250 ml /acre
- Confidor 200SL 250 ml /acre
- Mospilan 20SP 125 gm /acre
For chewing insects
- Proclaim 019EC 200 ml/acre
- Larvin 80DF 450 gm/acre
- Tracer 240SC 80 ml/acre
- Deltaphos 360EC 600 ml /acre
- Karate 2.5EC 400 ml/acre
Talstar 10EC 250 ml/acre
Shabana Hassan1, Sahar Bilal2 and Muhammad Usman Shafi3: MSc Hons, Department of Entomology, Faculty of Agricultural Sciences, University of the Punjab Lahore
