Dynamics of insect pests and predatory enemy communities in cotton fields in north of the Huaihe River, Anhui Province

The dynamics of insect pest and predatory enemy communities in cotton fields in north of Huaihe River, Anhui Province was studied.35 species of insect pests and 24 species of predatory enemies were found.The dominant species of insect pests are Aphis gossypii,Bemisia tabaci,Tetranychus cinnabarinus, and Adelphocoris spp., and the dominant species of predatory enemies are Singa pygmaea,Propylaea japonica,Pardosa T-insignita, Erigonidium graminicolum,Theridion octomaculatum,Nabis sinoferus,Orius similis and Paederus fuscipes.Among the dominant species, the distribution ratio of S.pygmaea, P.T-insignita, E.graminicolum, T.octomaculatum, O.similis and P.fuscipes on the cotton plants is:lower part ＞middle part＞upper part;for B.tabaci and Adelphocoris spp.,it is:upper part＞middle part＞lower part;for N. sinoferus,it is:upper part＞lower part＞middle part before July 30,and lower part＞upper part＞middle part after Aug.9;for A.gossypii, it is:upper part＞lower part＞middle part before June 20,but lower part＞upper part＞middle part after June 30;for P.japonica,it is:upper part＞middle part＞lowe r part befor e July 10,but lower part＞upper part＞middle part after July 20.T. cinnabarinus mainly exists in the lower part of the cotton plant in the prophase and then moves up.The evenness of the communities is relatively low during the early development stage of the cotton plant,but rises gradually during the middle development stage and declines eventually during late development stage.The change trend of the enemy community concentration is inversely related to its evenness.During the middle development stage of cotton,the community is most diverse.Species community diversity and evenness index has significant relationship with the guild community diversity,the correlation coefficient is 0.9904.