Abstract:By cage experiments, life tables of cotton aphid, Aphis gossypii, in transgenic cotton fields (cvs. GK12 and SGK321) were established to evaluate key factors affecting aphid populations. These studies were carried out in Nanpi County, Hebei Province in July, 2004 with the non-transgenic parental cotton varieties (cvs. Simian3 and Shiyuan321) as control. It showed that both GK12 and SGK321 had no significant impacts on natural control efficacy of the biological and non-biological death factors of cotton aphids. Except for the factor of natural death and others, predation was the key factor affecting population dynamics of cotton aphid. Rain ranked the second, parasitism by insects and pathogens had weak control efficacy. Except that cotton aphid had longer developmental period in SGK321 field, transgenic cotton GK12 and SGK321 had no adverse impacts on development and fecundity of cotton aphids. It indicated that predation was the key factor affecting population dynamics of cotton aphids in GK12 and SGK321 and their respective parental cotton fields. And impacts of GK12 and SGK321 on development and fecundity of cotton aphids were different.