These are located on the stems at the apical growing point, usually with one or more swollen pairs of leaves associated with them. Galled shoots are often prevented from flowering, but flowering is occasionally seen above the galled growing point. Post-emergence galls and associated leaves rot and turn black. After the apical growing region rots, the plant sends out a new shoot from a lower meristem.

Produces large (> 1cm diameter) spherical galls on the apical growing region of host plant stems (terminals). Stiling et al. (1992) described the life cycle of the midge on the marsh composite, sea oxeye,Borrichia frutescens (L.) de Candolle, which was its only known host plant at the time. Since this initial study, we have found two additional hosts of A. borrichiae, marsh elder, Iva frutescens L., and dune elder, Iva imbricata Walt.; like the sea oxeye, both are composites.