POPULATION DYNAMICS OF INSECT PESTS OF COTTON AND THEIR NATURAL ENIMIES

The present research work aimed to study the population dynamics of different insect pests of cotton and their natural enemies at the Research Farm of Agricultural University, Peshawar, Pakistan during 2009. Whitefly, Bemisia tabaci (Gennadius); aphids, Aphis gossypii (Glover); leafhopper, Amrasca biguttula biguttula (Ishida); leaf beetle, Cerotoma trifurcate (Forster); red cotton bug, Dyesdercus koenigii (Fabricius) were the major insect pests while ladybird, beetle Coccinella septempunctata (Linnaeus); spider, Dictyna sp. (Linnaeus) and ants, Solenopsis invicta (Buren) were the natural enemies recorded on cotton. Densities of insect pests and natural enemies peaked from June to October. Highest density of 5.78 tabaci leaf^-1 was recorded on 10th August, 2.61 gossypii leaf^-1 on 20th June, 6.56 biguttula biguttula leaf^-1 on 10th August, 0.89 trifurcate leaf^-1 on 30th August and 1.58 koenigii leaf^-1 on 9th October. The highest density of 1.42 C. septempunctata leaf^-1 on 10th August, 0.56 Dictyna sp. leaf^-1 on 19th September and 1.22 invicta leaf^-1 on 20th June were recorded. The pest and natural enemies completely disappeared after mid-October.