| The paper studied the population dynamics,the technique of manual trap and the prevention effect of Coccinella undecimpunctata Linnaeus against aphid in the cotton fields of south Xinjiang.The results showed that Coccinella undecimpunctata Linnaeus was key natural enemy affecting the population dynamics of Aplid gossypii Glover in different cotton varieties.The number of dominant species was over 80%.The population of Coccinella undecimpunctata Linnaeus appeared obviously a following relation with Aplid gossypii Glover and lagged about one week later behind Aplid gossypii Glover.The traped number of Coccinella undecimpunctata Linnaeus was related to the location of the trap boxes and trap materials in boxes.The number of trapped Coccinella undecimpunctata Linnaeus in the boxes hanged on the trees of the forest belt around the cotton field,placed on the ridge of field and in the cotton field was the most,few and the fewest,respectively.The number of trapped Coccinella undecimpunctata Linnaeus in the honey boxes,pollen and honey mixture boxes,pollen boxes and control boxes varied from large to less.Released to the center aphis-cotton plant in field,the overwintered Coccinella undecimpunctata Linnaeus could prevent cotton plants against Aphis harm.Compared with cotton without release of ladybird,the height of the center aphis cotton,the fruit branch number,the bud number,the boll number and the yield per plant increased 59.5%,20.3%,100%,81.4%,and 81.1%,repectivly. |