[Grey system analysis on dominant natural enemies influencing Aphis gosspyii population]

The populations of Aphis gosspyii and its natural enemies before cotton boll stage were investigated systematically in 1983, 1984, 1986, 1988, 1994 and 1995. The relationship between daily total predation of natural enemies and Aphis gosspyii population size was studied with the grey system theory and method, and the relational grade of various natural enemies to ideal superior natural enemies was analyzed. The results show that Propylaca japonica was the major natural enemy influencing Aphis gossypii, followed by Chrysopa septempunctata, then by Therdion octomaculatum and Erigonidium graminicola.