Cotton Leaf Folder
Sylepta derogata is also called as the cotton leaf folder. As the name is indicating the pest makes the leaves to roll. The older larvae roll the edges of leaves with the help of silken threads and feed on the leaf tissues after making roll. American cotton is worse affected. It is not a problem in BT Cotton. Like all the other pest of cotton the control of this pest should be planned after the determination of threshold levels. Biological control is considered to be optimum in case of the ideal conditions of temperature and humidity. During harsh conditions, chemical control is only option left. Attack of this pest is less on Native Cotton or Local Cotton.
Pink Boll Worm
Pectinophora gossypiella is one of the most destructive pests of cotton crop in Pakistan. It attacks the flowering stage when the female lays eggs on the base of flower. The larvae make a very small hole and move inside the flower. The affected boll fails to open or it opens in a very awkward fashion indicating the attack of pink boll worm. It hibernates in between the seeds and Double Seeds are also the best indication of the damaged seeds. Farmers should avoid the use of Double Seeds that are stuck together by the silken threads of pupal stage of this pest. Cotton sticks serve as the best hiding place for this insect. It is not a problem in BT Cotton.
American Boll Worm
Helicoverpa armigera is also called as the American bollworm and it is an important pest of chickpea and American Cotton. It is a polyphagous insect and is considered to damage a range of vegetable and other crops in Pakistan as well as other countries of South Asia. When it attacks the early stages it hollows the squares from inside and the damaged squares fall on the ground. It directly affects the cotton crop and results in lower yields. When the boll is mature it makes a prominent hole on the boll and results in the damage of the crop. The damage of American Bollworm is not observed in a uniform behavior rather it attacks in patches and affects the crop in patch. It shifts from one boll to another and damages dozens of bolls during life time. Biological control of this insect is the best option but in harsh conditions when biological control is not effective, chemical control serves as the only option for the control of American bollworm. It is not a problem in BT Cotton.
Phenococcus gossypiphilous was first reported in 2005 in Pakistan and in 2006-07 it affected the whole cotton belt of Pakistan. Life cycle of mealy bug is very rapid and it feeds on almost all kind of vegetables and flowers mainly due to the polyphagous habit. It damages the cotton crop by sucking the cell sap and decreasing the plant vigor. It also secretes some toxic saliva secretions that inhibit the growth and disturbs plant metabolism. Sometimes it can also secrete the cottony wax and when the attack exceeds the threshold level honey dew also increases in percentage and so is the sooty mold. Chemical control is not the only solution because the biological control of mealy bug served to control most of the pest population in the Cotton belts of Pakistan. IPM of any insect should focus on all the possible methods and techniques to ensure the discouragement of pest populations in a particular habitat or area.
Thrips tabaci is one of the most threatening pests of cotton, onion and garlic. The rasping sucking mouth parts of this insect damages the vegetative as well as the reproductive parts of many crops. In cotton the attack of thrips is greatly observed on the flowers and leaves where it congregates near the base of flowers or the leaves. Most of the farmers get the confusion in determining the attack of thrips. The mode of damage is different as compared to other insect pests of cotton. Crumpled and silvery appearance of leaves is the main sign of the thrips attack on American cotton. Insect Pest Management should be well directed in order to control the sucking as well as the chewing insect pests of cotton crop. In many countries like USA thrips is considered to be the vector of many viruses like the streak virus of peas and yellow spot of pineapple.
Amrasca biguttula is one of the most damaging pests of cotton crop in Pakistan. Damage of Cotton Jassid is very different as compared to that of other insect pests of cotton. Cup formation of leaves is observed in the peak of its attack. It also secretes the toxic secretions that are passed along with the saliva and the plant metabolism gets a greater shock due to the very presence of this particular insect pest of cotton. It also disturbs the boll formation as the boll formation is reduced after the attack of Jassid. It also affects the ladyfinger crop and also causes a greater damage to the winter vegetables which serves as an alternate source of food when the cotton season is not in progress.
Bemisia tabaci is said to be the most notorious pest of American cotton mainly due to its ability to transmit the CLCV also called as the Cotton Leaf Curl Virus. Mainly this insect pest damages the cotton crop in four ways. It sucks the cell sap and results in loss of vigor. It also injects the toxic saliva that results in a great damage to the cotton leaves. It sucks the cell sap and secretes the honey dew that invites the infestation of sooty mould. Sickly black appearance of the plant results in less absorption of sunlight and the photosynthesis process is adversely affected in one way or the other. Transmission of CLCV is one of the most important damage of cotton whitefly.