Gynoparous, oviparous, and apterous green peach aphids,Myzus persicae(Sulzer), preferred radish,Raphanus sativusL., to the winter host, peach,Prunus persicaBatsch, in laboratory tests of settling behavior. Preference for radish was strongest in the apterae and weakest in the oviparae; however, in all cases the degree of preference was significant (P= 0.01). Gynoparae discriminated between peach and a nonhost species,Acer saccharinumL., although few aphids settled on either species during the test. Although feeding preferences may allow green peach aphid to discriminate between tree species, these results indicate that such preferences cannot explain the movement of migrants from secondary to primary hosts. Apterae discriminated readily between various secondary hosts. Marked differences in preference occurred even between species which have been shown to be highly suitable for reproduction. Rates of settling were higher on preferred hosts than nonpreferred hosts, indicating that the rate of interplant movement may be significantly greater on nonpreferred hosts.