Overwintering of the Spirea Aphid, Aphis citricola VAN DER GOOT (Homoptera : Aphididae) on Citrus and Spirea Plants

Abstract

Some differences in overwintering habits were noted between the populations of Aphis citricola on Spiraea thunbergii and on Citrus unshiu. A. citricola laid eggs at almost the same time on both plants. The aphid overwintered holocyclically and unholocyclically on spirea but only holocyclically on citrus. The time of egg hatching was different on the two plants, those on spirea hatching more than a month earlier than those on citrus. The sprouting of the host plant did not lead directly to the egg eclosion. The possibility was suggested that the two overwintering populations might differ from one another in their life cycles and that a biotypic differentiation might occur in this aphid. The appearance of emigrants on spirea was more than twenty days earlier than on citrus when the citrus grove invasion began. It was suggested that the spirea emigrants might not play a major role in the spring infestation in citrus groves but that the citrus overwintering population might be important in this infestation.