Abstract: The green ash, Fraxinus pennsylvanica Marsh., is infested with a leafcurl ash aphid in Beijing, China. Colonies of compact aphids live in curled leaves on the tips of twigs throughout the vegetation period. It causes malformations and some curled leaves turn to yellow. It was identified as an alien species, the Nearctic species Prociphilus fraxinifolii  (Riley, 1879). This is the first record of the species in China. The present paper described its diagnostic characteristics and recorded five predatory natural enemies (Harmonia axyridis, Chrysopa pallens, Episyrphus balteata, Deraeocoris punctulatus and Deraeocoris ater) and three attending ants (Camponotus japonicus, Formica fusca, and Lasius niger) of this aphid found in Beijing.

Key words: Prociphilus fraxinifolii, Fraxinus pennsylvanica, alien insect species, morphology, predatory natural enemies